Tesi: "Expansion of universe"

1

Burrage, Clare Joanna. "Scalar fields and the accelerated expansion of the universe". Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611090.

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2

Humphreys, Neil Paul. "Obervational analysis of the inhomogeneous universe". Thesis, University of Portsmouth, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310380.

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3

Davis, Tamara Maree Physics Faculty of Science UNSW. "Fundamental aspects of the expansion of the universe and cosmic horizons". Awarded by:University of New South Wales. Physics, 2004. http://handle.unsw.edu.au/1959.4/20640.

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We use standard general relativity to clarify common misconceptions about fundamental aspects of the expansion of the Universe. In the context of the new standard Lambda-CDM cosmology we resolve conflicts in the literature regarding cosmic horizons and the Hubble sphere (distance at which recession velocity equals c) and we link these concepts to observational tests. We derive the dynamics of a non-comoving galaxy and generalize previous analyses to arbitrary FRW universes. We also derive the counter-intuitive result that objects at constant proper distance have a non-zero redshift. Receding galaxies can be blueshifted and approaching galaxies can be redshifted, even in an empty universe for which one might expect special relativity to apply. Using the empty universe model we demonstrate the relationship between special relativity and Friedmann-Robertson-Walker cosmology. We test the generalized second law of thermodynamics (GSL) and its extension to incorporate cosmological event horizons. In spite of the fact that cosmological horizons do not generally have well-defined thermal properties, we find that the GSL is satisfied for a wide range of models. We explore in particular the relative entropic "eworth"e of black hole versus cosmological horizon area. An intriguing set of models show an apparent entropy decrease but we anticipate this apparent violation of the GSL will disappear when solutions are available for black holes embedded in arbitrary backgrounds. Recent evidence suggests a slow increase in the fine structure constant over cosmological time scales. This raises the question of which fundamental quantities are truly constant and which might vary. We show that black hole thermodynamics may provide a means to discriminate between alternative theories invoking varying constants, because some variations in the fundamental "econstants"e could lead to a violation of the generalized second law of thermodynamics.

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4

QUIROGA, ALEXANDER ARGUELLO. "IMPACT OF THE COSMIC NEUTRINO BACKGROUND IN THE EXPANSION OF THE UNIVERSE". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2009. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=14883@1.

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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Os neutrinos são produzidos copiosamente no Universo primordial e são hoje as espécies mais abundantes de partículas após os fótons. Com a descoberta da oscilação de neutrinos sabe-se que eles possuem massa. Os efeitos de neutrinos na formação de estruturas têm sido muito estudados e a comparação com os dados observacionais estabelece limites sobre a soma de suas massas. Nesta monografia abordamos outro aspecto dos neutrinos em cosmologia que tem sido pouco estudado na literatura: a sua influência na expansão global e suas possíveis implicações observacionais. Um aspecto interessante dos neutrinos do fundo cósmico é que, dentro dos limites actuais em suas massas, ao menos uma espécie deve ter passado de um regime relativístico a não-relativístico desde o desacoplamento matéria-radiação até o presente. Essa mudança de regime poderia acarretar em efeitos observacionais característicos desse processo. Neste trabalho investigamos a equação de estado dos neutrinos em função de sua massa e sua temperatura. A partir desse resultado, obtemos a taxa de expansão e a distância de luminosidade em função do desvio para o vermelho para um Universo contendo neutrinos massivos, além de matéria escura, constante cosmológica e radiação. Embora espera-se que o impacto dos neutrinos nessas quantidades observáveis seja pequeno, o objetivo deste trabalho é verificar se ele pode ser mensurável no contexto da emergente cosmologia de presição.
Neutrinos are produced copiously in the primordial Universe and today they are the most abundant specie of particles after the photons. With the discovery of neutrinos oscillation it is known that at least two of them have mass, although the absolute values are unknown. The effects of massive neutrinos in the large scale structure formation have been much studied and the comparison with observational data establishes limits over the neutrinos mass sum. In this dissertation we broach other aspect of neutrinos in cosmology which has been few studied in literature: its influence in the global expansion and the possible observational implications. An interesting aspect of cosmic neutrinos background is that inside the present masses limits at least one specie must have passed from a relativistic regime to a non-relativist one, since the matter-radiation decoupling until now. This change in regime could cause observational effects characteristics of this process. In this research we investigate the neutrinos state equation in function of their mass and temperature. From this result, we obtain the expansion rate and the luminosity distance in function of the Universe red-shift considering the presence of massive neutrinos, besides the dark matter, cosmological constant and radiation. Even through we expect that the neutrinos impact in these observable be small, the objective of this work is to verify if it can be measured in the context of the emergent precision cosmology.

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5

Ali, Sahba Yahya Hamid. "Probing the expansion history of the universe using upernovae and Baryon Acoustic Oscillations". University of the Western Cape, 2016. http://hdl.handle.net/11394/5054.

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Philosophiae Doctor - PhD
The standard model of cosmology (the ɅCDM model) has been very successful and is compatible with all observational data up to now. However, it remains an important task to develop and apply null tests of this model. These tests are based on observables that probe cosmic distances and cosmic evolution history. Supernovae observations use the so-called `standard candle' property of SNIa to probe cosmic distances D(z). The evolution of the expansion rate H(z) is probed by the baryon acoustic oscillation (BAO) feature in the galaxy distribution, which serves as an effective `standard ruler'. The observables D(z) and H(z) are used in various consistency tests of ɅCDM that have been developed. We review the consistency tests, also looking for possible new tests. Then the tests are applied, first using existing data, and then using mock data from future planned experiments. In particular we use data from the recently commissioned Dark Energy Survey (DES) for SNIa. Gaussian Processes, and possibly other non-parametric methods, used to reconstruct the derivatives of D (z) and H (z) that are needed to apply the null tests of the standard cosmological model. This allows us to estimate the current and future power of observations to probe the ɅCDM model, which is the foundation of modern cosmology. In addition, we present an improved model of the HI galaxy number counts and bias from semi-analytic simulations, and we use it to calculate the expected yield of HI galaxies from surveys with a variety of phase 1 and 2 SKA configurations. We illustrate the relative performance of the different surveys by forecasting errors on the radial and transverse scales of the BAO feature. We use the Fisher matrix method to estimate the error bars on the cosmological parameters from future SKA HI galaxy surveys. We find that the SKA phase 1 galaxy surveys will not contend with surveys such as the Baryon Oscillation Spectroscopic Survey (BOSS) whereas the full "billion galaxy survey" with SKA phase 2 will deliver the largest dark energy Figure of Merit of any current or future large-scale structure survey.
South African Square Kilometre Array Project (SKA) and German Academic Exchange Service (DAAD)

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6

Gupta, Rahul. "Supernova Cosmology in an Inhomogeneous Universe". Thesis, Stockholm University, Stockholm University, Department of Physics, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-42162.

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The propagation of light beams originating from synthetic ‘Type Ia’ supernovae, through an inhomogeneous universe with simpliﬁed dynamics, is simulated using a Monte-Carlo Ray-Tracing method. The accumulated statistical (redshift-magnitude) distribution for these synthetic supernovae observations, which is illustrated in the form of a Hubble diagram, produces a luminosity proﬁle similar to the form predicted for a Dark-Energy dominated universe. Further, the amount of mimicked Dark-Energy is found to increase along with the variance in the matter distribution in the universe, converging at a value of Ω_X ≈ 0.7.

It can be thus postulated that at least under the assumption of simpliﬁed dynamics, it is possible to replicate the observed supernovae data in a universe with inhomogeneous matter distribution. This also implies that it is demonstrably not possible to make a direct correspondence between the observed luminosity and redshift with the distance of a cosmological source and the expansion rate of the universe, respectively, at a particular epoch in an inhomogeneous universe. Such a correspondences feigns an apparent variation in dynamics, which creates the illusion of Dark-Energy.

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7

Mazumdar, Anupam. "Dynamics of inflation". Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325580.

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8

de, Cruz Pérez Javier. "Implications of Dynamical Dark Energy in the expansion of the Universe and the Structure Formation". Doctoral thesis, Universitat de Barcelona, 2021. http://hdl.handle.net/10803/671792.

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En aquesta tesi s’estudien diferents models cosmològics, tots ells caracteritzats per considerar, de manera efectiva, una lleu evolució temporal de l’Energia Fosca, en contrast amb l’actual model estàndard de la cosmologia. El terme Energia Fosca s’utilitza per fer referència a una misteriosa forma d’energia que sembla impregnar tots els racons del Univers i que provoca que les galàxies s’allunyin les unes de les altres. El ritme predit d’expansió del Univers varia d’un model a un altre així com la quantitat d’estructura observada i la distribució d’aquesta. Degut al bon moment de la cosmologia observacional tenim a la nostre disposició una gran quantitat de dades que ens permeten posar a prova els diferents models existents. Un exemple d’aquests models, seria el Running Vacuum Model (RVM), que ha estat estudiat en detall en aquesta tesi i que considera una expressió per la densitat d’energia del buit motivada en el context de les Teories Quàntiques de Camp. Un altre exemple de models cosmològics serien els anomenats models de camp escalar que suposen que l’equació d’estat de l’Energia Fosca, en el moment present, és lleugerament diferent del valor predit pel model estàndard. No noées s’han considerat models acomodats dins del marc de la teoria de la Relativitat General, sinó que també s’han estudiat les prediccions teòriques del model presentat per Brans i Dicke al 1961 i que resulta ser el primer intent d’extensió de la teoria d’Einstein. El model de Brans i Dicke està caracteritzat pel fet que la interacció gravitatòria està no només mediada per un camp tensorial, sinó també per un camp escalar. Les prediccions teòriques dels diferents models estudiats, tant a nivell de background com a nivell de pertorbacions, han sigut contrastades amb les mes recents dades cosmològiques revelant que l'anteriorment esmentada evolució temporal de l’Energia Fosca ajuda a rebaixar, de manera considerable, algunes de les tensions que afecten al model estàndard. La comparació teoria-observacions s’ha dut a terme mitjançant una rigorosa metodologia que involucra diferents eines estadístiques. Per tant les conclusions obtingudes al llarg d’aquesta tesi es basen en un procés robust i en un estudi detallat dels diferents models cosmològics considerants.
The high quality observations performed during the last two decades, have allowed to demonstrate, with high confidence range, that the Universe is in expansion and to be more precise in accelerated expansion. In order to explain the accelerated evolution the name of dark energy was coined. It refers to a some mysterious form of diffuse energy presumably permeating all corners of the Universe as a whole. We may say that the canonical picture of our Universe defined in the framework of General Relativity, whose field equation were found by Einstein in 1917, is built upon the assumption that the observed acceleration is caused, in fact, by a rigid cosmological constant term denoted by Λ. Thanks to the aforementioned cosmological measurements, we have been able to pin down its value to an impressive level. Dark energy is not the only element, beyond the conventional baryons and photons, required by the observations since we also need large amounts of what is commonly call as dark matter. We call such an overall picture of the Universe the “concordance (or standard) cosmological model” or simply ΛCDM. Therefore, we attribute the observed accelerated expansion of the Universe to the existence of a repulsive force, exerted by the Λ term, which works against the attractive gravitational force and tends to push the clusters of galaxies apart at a speed continuously increasing with the cosmic expansion. Throughout this thesis a wide variety of models, beyond the standard model have been studied. The corresponding analyses have been carried out by studying in detail the theoretical predictions at the background and perturbation level, with the purpose of testing them with the large amount of cosmological data which we currently we have access to. The ultimate goal is to see if we can detect signals of new physics that help to alleviate some of the tensions that affect the ΛCDM. The concordance model, has remained robust and unbeaten for a long time since it is roughly consistent with a large body of cosmological data. Because of this fact, it is not reasonable to look for models with a very different behaviour than the ΛCDM, but to study models that exhibit small departures with respect to the standard model in key aspects. We have studied the Running Vacuum Models (RVM) in depth. They are characterized by having a time-evolving vacuum energy density, whose functional expression is motivated in the context of Quantum Field Theory in curved space-time. It is fundamental that its expression contains a constant term, which mimics the standard behaviour in order to first generate the transition from a decelerated to an accelerated Universe and to ensure that the fit of the structure formation data is not ruined. We have also studied the Peebles & Ratra model, which is a particularly successful scalar field model φCDM for which the potential takes the form V (φ) ∼ φ−α . The dimensionless parameter α encodes the extra degree of freedom that this model has with respect to the standard model. It is found to be small and positive, therefore V (φ) can mimic and approximate cosmological constant that is decreasing slowly with time. In the late Universe the contribution of the scalar field, φ, surfaces over the matter density, thus becoming the dominant component. Not all the models studied are motivated within a theoretical framework, since we have also considered some interesting phenomenological approaches. Last but not least, at the end of the thesis the Brans & Dicke (BD) gravity model was studied in detail. The main feature of this model is that the Newtonian constant coupling GN is replaced by a dynamical scalar field G(t) = 1/ψ(t), coupled to the curvature. As a consequence the gravitational interaction is not only mediated by the metric field, as in the General Relativity case but also for the aforementioned scalar field ψ. The obtained results clearly point out to an interesting conclusion, those models which consider an effective time-evolving dark energy are able to alleviate some of the tensions affecting the ΛCDM. Among the different tensions there are two that stand out, namely the σ8 -tension and the H0-tension.

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9

Helou, Alexis. "Beyond the trapping horizon : the apparent universe & the regular black hole". Sorbonne Paris Cité, 2015. http://www.theses.fr/2015USPCC140.

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Dans le contexte de la Relativité Générale, le concept d'horizon permet de séparer l'espace-temps en zones de comportement causal différent. En particulier l'horizon apparent, et la notion très proche d'horizon de confinement, sont définis à partir de grandeurs locales. Nous sélectionnons ces horizons comme l'outil pertinent pour décrire les situations dynamiques à symétrie sphérique, telles que le trou noir ou la cosmologie. Le principe d'Holographie indique en effet que l'information contenue dans un volume donné serait encodée sur la surface renfermant le volume. Ainsi l'horizon apparent contiendrait des informations sur le trou noir qu'il délimite ou sur l'Univers qu'il borne. Dans cette optique, nous appliquons les lois de la thermodynamique à l'horizon apparent cosmologique, en utilisant un ensemble d'outils adaptés à la symétrie sphérique : le vecteur de Kodama, l'énergie de Misner-Sharp, la première loi unifiée. Ceci nous permet de retrouver les équations de Friedmann qui régissent la dynamique de notre Univers. Un paramètre de température thermodynamique est ensuite calculé, qui caractérise une émission à l'horizon. Ceci est ensuite généralisé aux trous blancs et cosmologies en contraction. Enfin nous étudierons le rôle de l'horizon apparent dans le paradoxe de l'information des trous noirs
In the context of General Relativity, the concept of horizon divides the spacetime into regions of different causal behaviour. In particular, the apparent horizon and closely related trapping horizon are defined from local quantities. We select these horizons as the relevant tool to describe spherically symmetric, dynamical situations, such as black holes or cosmology. Indeed the Holographic principle indicates that the information contained in the bulk of a given region, would be encoded on the boundary surface of the region. Then the apparent horizon would contain information on the black hole or on the Universe it bounds. In this optic, we apply the laws of thermodynamics to the cosmological apparent horizon, using a set of tools well-suited to spherical symmetry : the Kodama vector, the Misner-Sharp energy, the unified first law. This will allow us to recover the Friedmann equations, which govern the dynamics of our Universe. A thermodynamical parameter identified as a temperature is then computed, which characterizes the emission at the horizon. This is then generalized to white holes and contracting cosmologies. Finally we study the role of the apparent horizon in the information loss paradox for black holes

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10

Wiegand, Alexander [Verfasser]. "The inhomogeneous Universe : its average expansion and cosmic variance / Alexander Wiegand. Fakultät für Physik - Cosmology and Astroparticle Physics". Bielefeld : Universitätsbibliothek Bielefeld, Hochschulschriften, 2012. http://d-nb.info/1026077605/34.

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11

Cognola, Guido, Emilio Elizalde, Shin'ichi Nojiri, Sergei D. Odintsov e Sergio Zerbini. "String-inspired Gauss-Bonnet gravity reconstructed from the universe expansion history and yielding the transition from matter dominance to dark energy". American Physical Society, 2007. http://hdl.handle.net/2237/8845.

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12

Bamba, Kazuharu, Shin'ichi Nojiri e Sergei D. Odintsov. "Inflationary cosmology and the late-time accelerated expansion of the universe in nonminimal Yang-Mills- F(R) gravity and nonminimal vector-F(R) gravity". American Physical Society, 2008. http://hdl.handle.net/2237/11280.

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13

Benitez, Herrera Sandra Verfasser], Wolfgang [Akademischer Betreuer] Hillebrandt e Shawn [Akademischer Betreuer] [Bishop. "Model-Independent Approach to Reconstruct the Expansion History of the Universe with Type Ia Supernovae / Sandra Benitez Herrera. Gutachter: Wolfgang Hillebrandt ; Shawn Bishop. Betreuer: Wolfgang Hillebrandt". München : Universitätsbibliothek der TU München, 2013. http://d-nb.info/1046670786/34.

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14

Alimi, Jean-Michel. "Contributions : instabilite gravitationnelle dans un univers en expansion et formation des grandes structures, effets ponderomoteurs dans les plasmas magnetises". Paris 6, 1987. http://www.theses.fr/1987PA066234.

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Analyse de la fonction de correlation spatiale des galaxies, obtenue a partir de catalogues de galaxies, selon differentes procedures. La distribution des galaxies isolees dans le catalogue cfa est etudiee. Etude du collapse gravitationnel non lineaire de particules sans collision, du point de vue analytique et numerique. On montre l'importance du traitement tridimensionnel de ces processus gravitationnels et quelles peuvent en etre les consequences sur la formation des galaxies

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15

Duran, Sancho Ivan. "Constraining Cosmological Models of Dark Energy". Doctoral thesis, Universitat Autònoma de Barcelona, 2013. http://hdl.handle.net/10803/125917.

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Avui en dia, l'Univers sembla estar experimentant una fase d'expansió accelerada, com ho demostren les dades de supernoves i posteriorment corroborada per una sèrie de mesuraments cosmològiques -molt recentment pel satèl·lit Planck. Mentre que aquesta expansió pot ser descrit en la teoria de la gravetat d'Einstein mitjançant la invocació de l'existència d'una positiva, però extremadament petita constant cosmològica, Λ, connectat al buit quàntic, s'han proposat moltes alternatives. A grans trets, el contingut d'energia de l'univers actual es pot dividir en 5% de la matèria bariònica i el 95% d'un invisible (conegut com el "sector fosc", perquè els seus components no interactuen electromagnèticament), el 25% del qual constituït per matèria no-relativista, partícules massives d'interacció feble ("matèria fosca freda") i un 75% d'un component amb una enorme pressió negativa, l'anomenada "energia fosca". La naturalesa d'aquest últim component és completament desconegut, això justifica que s'han proposat molts candidats "de prova". De moment, la més simple i de més èxit és la constant cosmològica, esmentada anteriorment. No obstant això, pateix de dos inconvenients principals a nivell teòric: el problema de la coincidència i el problema del “fine-tunning”. L'objectiu d'aquesta memòria és proposar i ajustar els models cosmològics de l'energia fosca que eviten aquestes dificultats. Aquesta tesi està organitzada de la següent manera: Els capítols § 2, § 3 i § 4 s'introdueixen conceptes bàsics utilitzats en considerar els diferents models que conformen el nostre treball de recerca. Els següents capítols se centren en els diferents models cosmològics. Al § 5, l'energia fosca compleix el principi hologràfic i es postula que interactua (també sense gravetat) amb la matèria fosca. El principi hologràfic estableix una escala de longitud, en aquest cas la longitud d' Hubble, és a dir, la distància que limita els esdeveniments causalment connectats. Al capítol § 6, s'estudia amb més profunditat el model anterior, i es presenta una alternativa al mateix. Tots dos models comparteixen l'evolució fons idèntica però cada component es comporta de manera diferent, la qual cosa indueix un comportament divers quan es consideren les pertorbacions. Això permet discriminar observacionalment un model de l'altre. Un model d'energia fosca hologràfica més es proposa en el § 7, aquest amb l’escala de longitud determinada per el Radi de Ricci (és a dir, la mida màxima d'una pertorbació que condueix a un forat negre). Un cop més, es suposa una interacció no-gravitacional entre l'energia fosca i la matèria fosca. Al § 8, s'estudia un model unificat (amb una unificació entre la matèria fosca ad energia fosca) proposat anteriorment. Atès que l'espai de paràmetres que s'ajusta a les dades observacionals és molt petit (i també en vista del seu interès teòric), descomponem el component únic en matèria fosca freda i buit que interactuen entre ells. Com a conseqüència, l'espai de paràmetres permesos queda augmentada considerablement. Encara que els models esmentats anteriorment imiten a nivell de fons el model ΛCDM estàndard, els components foscos evolucionen de manera molt diferent. Per estudiar-los rigorosament, els codis numèrics de les pertorbacions cosmològiques han de ser adequadament modificats, amb l'inconvenient d'incrementar notablement el temps de càlcul. Aquest fet és alleujat al § 9, on un nou mètode per calcular l'espectre de potència dels models d'energia fosca és proposat. Finalment, en el § 10 tres noves parametritzacions del paràmetre de desacceleració, amb base a arguments termodinàmics sòlids, es proposen i es contrasta amb les dades observacionals.
Nowadays the Universe appears to be undergoing a phase of accelerated expansion, as witnessed by supernovae data and later corroborated by a host a cosmological measurements -very recently by the Planck satellite. While this expansion can be described in Einstein’s theory of gravity by invoking the existence of a positive but exceedingly small cosmological constant, Λ, connected to the quantum vacuum, many alternative, and sometimes sophisticated, explanations have been proposed. Roughly, the energy content of the present universe can be split into 5% of baryonic matter and 95% of a non-visible (dubbed the “dark sector” because its components do not interact electromagnetically) whose 25% consists of non-relativistic, weakly interacting massive particles (“cold dark matter”) and a 75% of a component with a huge negative pressure, the so-called “dark energy”. The nature of the latter component is completely unknown; this justifies that many “trial” candidates have been proposed. By far, the simplest and most successful one is the cosmological constant, mentioned above. However, it suffers from two main drawbacks at the theoretical level: the coincidence problem and the fine tuning problem. The aim of this Memoir is to propose and constrain cosmological models of dark energy that circumvent these difficulties. This Memoir is organized as follows: The Chapters §2, §3 and §4 introduce basic concepts widely used when considering the different models that conforms our research work. The following Chapters focus on the different cosmological models. In §5 dark energy is considered connected to the holographic principle and posits that it interacts (also non-gravitationally) with dark matter. The holographic principle sets a length scale, in this case the Hubble length, i.e., the scale of the causally connected events. In §6 the previous model is studied more deeply and an alternative to it is presented. Both models share identical background evolution but each component behaves differently, which induces a diverse behavior at the perturbative level. This allows to observationally discriminate one model from the other. A further holographic dark energy model is proposed in §7; this one based on the Ricci length (i.e., the maximum size a perturbation can have leading to a black hole). Again, a non-gravitational interaction is assumed between dark energy and dark matter. In §8, a unified dark model (featuring a unification between dark matter ad dark energy) previously proposed is studied. Since the parameter space that fits the observational data is very narrow (and also in view of its theoretical interest), we decompose the single energy component into cold dark matter and quantum vacuum interacting with one another. As a consequence the allowed parameter space gets substantially augmented. Although the models mentioned above mimic at the background level the standard ΛCDM model, the dark components evolve very differently. To rigorously study them, the numerical codes for the cosmological perturbations must be suitably modified, with the drawback of notably increasing the computational time. This is much alleviated in §9 where a novel method to calculate the matter power spectrum of dark energy models is proposed. Finally, in §10 three model independent parameterizations of the deceleration parameter, based on solid thermodynamic arguments, are proposed and contrasted with the observational data.

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16

Ntelis, Pierros. "Probing Cosmology with the homogeneity scale of the universe through large scale structure surveys". Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC200/document.

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Cette thèse présente ma contribution à la mesure de l’échelle d’homogénéité à l’aide de galaxies, avec l’interprétation cosmologique des résultats. En physique, tout modèle est constitué par un ensemble de principes. La plupart des modèles de cosmologie sont basés sur le principe cosmologique, qui indique que l’univers est statistiquement homogène et isotrope à grande échelle. Aujourd’hui, ce principe est considéré comme vrai car il est respecté par ces modèles cosmologiques qui décrivent avec précision les observations. Cependant, l’isotropie de l’univers est maintenant confirmée par de nombreuses expériences, mais ce n’est pas le cas pour l’homogénéité. Pour étudier l’homogénéité cosmique, nous proposons un postulat d’homogénéité cosmique. Depuis 1998, les mesures des distances cosmiques à l’aide de supernovae de type Ia, nous savons que l’univers est maintenant en phase d’expansion accélérée. Ce phénomène s’explique par l’ajout d’une composante énergétique inconnue, appelée énergie sombre. Puisque l’énergie noire est responsable de l’expansion de l’univers, nous pouvons étudier ce fluide mystérieux en mesurant le taux d’expansion de l’univers. L’échelle d’oscillation acoustique Baryon (BAO). En mesurant cette échelle à différents moments de la vie de notre univers, il est alors possible de mesurer le taux d'expansion de l’univers et donc de caractériser cette énergie sombre. Alternativement, nous pouvons utiliser l’échelle d’homogénéité pour étudier cette énergie sombre. L’étude l’échelle de l’homogénéité et l’échelle BAO réclament l’étude statistique du regroupement de la matière de l’univers à grandes échelles, supérieure à plusieurs dizaines de Megaparsecs. Les galaxies et les quasars sont formés dans les vastes surdensités de la matière et ils sont très lumineuses: ces sources tracent la distribution de la matière. En mesurant les spectres d’émission de ces sources en utilisant de larges études spectroscopiques, telles que BOSS et eBOSS, nous pouvons mesurer leurs positions. Il est possible de reconstruire la distribution de la matière en trois dimensions en volumes gigantesques. Nous pouvons ensuite extraire divers observables statistiques pour mesurer l’échelle BAO et l’échelle d’homogénéité de l’univers. En utilisant les catalogues de diffusion de données 12 de la version 12 de données, nous avons obtenu une précision sur l’échelle d’homogénéité réduite de 5 par rapport la mesure de WiggleZ. À grande échelle, l’univers est remarquablement bien décrit en ordre linéaire selon le modèle LCDM, le modèle standard de la cosmologie. En général, il n’est pas nécessaire de prendre en compte les effets non linéaires qui compliquent le modèle à petites échelles. D’autre part, à grande échelle, la mesure de nos observables devient très sensible aux effets systématiques. Ceci est particulièrement vrai pour l’analyse de l’homogénéité cosmique, qui nécessite une méthode d’observation. Afin d’étudier le principe d’homogénéité d’une manière indépendante du modèle, nous explorons une nouvelle façon d’inférer des distances en utilisant des horloges cosmiques et SuperNovae de type Ia. C'est la théorie la plus couramment utilisée dans le domaine des hypothèses astrophysiques
This thesis exposes my contribution to the measurement of homogeneity scale using galaxies, with the cosmological interpretation of results. In physics, any model is characterized by a set of principles. Most models in cosmology are based on the Cosmological Principle, which states that the universe is statistically homogeneous and isotropic on a large scales. Today, this principle is considered to be true since it is respected by those cosmological models that accurately describe the observations. However, while the isotropy of the universe is now confirmed by many experiments, it is not the case for the homogeneity. To study cosmic homogeneity, we propose to not only test a model but to test directly one of the postulates of modern cosmology. Since 1998 the measurements of cosmic distances using type Ia supernovae, we know that the universe is now in a phase of accelerated expansion. This phenomenon can be explained by the addition of an unknown energy component,which is called dark energy. Since dark energy is responsible for the expansion of the universe, we can study this mysterious fluid by measuring the rate of expansion of the universe. Nature does things well: the universe has imprinted in its matter distribution a standard ruler, the Baryon Acoustic Oscillation (BAO) scale. By measuring this scale at different times in the life of our universe, it is then possible to measure the rate of expansion of the universe and thus characterize this dark energy. Alternatively, we can use the homogeneity scale to study this dark energy. Studying the homogeneity and the BAO scale requires the statistical study of the matter distribution of the universe at large scales, superior to tens of Megaparsecs. Galaxies and quasars are formed in the vast overdensities of matter and they are very luminous: these sources trace the distribution of matter. By measuring the emission spectra of these sources using large spectroscopic surveys, such as BOSS and eBOSS, we can measure their positions. It is thus possible to reconstruct the distribution of matter in 3 dimensions in gigantic volumes. We can then extract various statistical observables to measure the BAO scale and the scale of homogeneity of the universe. Using Data Release 12 CMASS galaxy catalogs, we obtained precision on the homogeneity scale reduced by 5 times compared to WiggleZ measurement. At large scales, the universe is remarkably well described in linear order by the ΛCDM-model, the standard model of cosmology. In general, it is not necessary to take into account the nonlinear effects which complicate the model at small scales. On the other hand, at large scales, the measurement of our observables becomes very sensitive to the systematic effects. This is particularly true for the analysis of cosmic homogeneity, which requires an observational method so as not to bias the measurement In order to study the homogeneity principle in a model independent way, we explore a new way to infer distances using cosmic clocks and type Ia SuperNovae. This establishes the Cosmological Principle using only a small number of a priori assumption, i.e. the theory of General Relativity and astrophysical assumptions that are independent from Friedmann Universes and in extend the homogeneity assumption

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Sainte, Agathe Victoria de. "Mesure de la position du pic d'oscillations acoustiques baryoniques dans les forêts Lyα et Lyβ des spectres des quasars du relevé eBOSS-SDSS IV". Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS373.

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La propagation des oscillations acoustiques baryoniques a laissé une empreinte dans la répartition de la matière de l’univers, visible sous la forme d’un excès de probabilité pour deux objets d’être séparés par une distance égale à l’échelle acoustique. La mesure de l’échelle acoustique dans la fonction de corrélation à deux points de la matière au redshift z, parallèlement et perpendiculairement à la ligne de visée donne accès, respectivement, aux rapports DH(z)/rd et DM(z)/rd où DH est la distance de Hubble, DM la distance angulaire comobile et rd l’horizon acoustique. On peut suivre la répartition de la matière en utilisant les absorptions Lyman-alpha visibles, sous la forme de forêts, dans les spectres des quasars à haut redshift. Puisque chaque spectre donne accès une centaine d’absorptions, cela permet de mesurer l’échelle acoustique même quand la densité de quasars observés est faible. Dans cette thèse, je décris le processus d’analyse qui, en utilisant environ 200 000 spectres de quasars du relevé eBOSS-SDSS IV, aboutit aux mesures DH(2.34)/rd = 8.86+/-0.29 et DM(2.34)/rd = 37.41+/-1.86. En combinant ces résultats avec les mesures de l’échelle acoustique à d’autres redshifts, j’obtiens la plus forte contrainte actuelle, à bas redshift, sur les paramètres Omega-m et Omega-Lambda dans le cadre du modèle Lambda-CDM
The propagation of the baryonic acoustic oscillations has been unprinted in the matter distribution in the Universe as a probability excess for two objets to be separated by the acoustic scale. Measuring the acoustic scale in the matter 2 point correlation function at redshift z, along and transversally to the line-of-sight, gives access to the DH(z)/rd et DM(z)/rd ratios, with DH the Hubble distance, DM the comoving angular distance and rd the acoustic horizon. We are able to trace the matter in the Universe by using the Lyman-alpha absorptions which shape the spectra of the high redshift quasars. Since each spectrum contain hundreds of absorption, this allow us to measure the acoustic scale even if the observed quasar density is low. In this thesis, I describe the analysis of about 200,000 spectra from the eBOSS-SDSS IV survey which conducts to the measurements DH(2.34)/rd = 8.86 0.29 et DM(2.34)/rd = 37.41 1.86. By combining these results with measurements of the acoustic scale at other redshifts, I obtain the strongest current constraints at low redshift on the Omega-m and Omega-Lambda Lambda-CDM parameters

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Comparat, Johan. "Baryonic acoustic oscillations with emission line galaxies at intermediate redshift : the large-scale structure of the universe". Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4720/document.

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J'ai démontrer la faisabilité de la sélection de la cible pour les galaxies en ligne des émissions lumineuses. Je comprends maintenant les principaux mécanismes physiques de conduite de l'efficacité d'une sélection, en particulier le rapport à la photométrie de parent. Une question reste perplexe, je ne pouvais pas encore estimer quantitativement l'impact de la poussière sur l'efficacité de la sélection. J'espère que d'aborder cette question avec l'ensemble des données décrites dans le chapitre 4.En dehors de la ligne de sélection de la cible de la galaxie d'émission, j'ai étudié, au premier ordre, les deux principales erreurs systématiques sur la détermination de l'échelle BAO nous attendent en raison de l'utilisation galaxies en ligne des émissions comme traceurs de la question. J'ai d'abord montré le caractère incomplet de la distribution redshift, en raison de la mesure du décalage spectral avec [Oii], est lié à la résolution instrumentale. Je trouve qu'il ya deux régimes intéressants. Pour une observation des plus brillants [OII] émetteurs, une résolution modérée est suffisante, alors que pour une enquête plus faible, la plus haute de la résolution le meilleur. Deuxièmement, j'ai estimé le biais de la galaxie linéaire des sélections discuté avant et je trouve qu'ils sont très biaisés. D'une part, ce sont d'excellentes nouvelles pour les observateurs, comme le temps nécessaire pour observer à un signal donné au bruit dans le spectre de puissance diminue avec le carré de la partialité. D'autre part, elle constitue un nouveau défi pour les algorithmes de reconstruction et la fabrication de catalogues simulacres
In this PhD, I demonstrate the feasibility of the target selection for bright emission line galaxies. Also I now understand the main physical mechanisms driving the efficiency of a selection, in particular the relation to the parent photometry. A puzzling issue remains, I could not yet estimate quantitatively the impact of the dust on the selection efficiency. I hope to address this question with the data set described in chapter 4.Apart from the emission line galaxy target selection, I investigated, at first order, the two main systematic errors on the determination of the BAO scale we expect due to using emission line galaxies as tracers of the matter. First I showed the incompleteness in the redshift distribution, due to the measurement of the redshift with [Oii], is related to the instrumental resolution. I find there are two interesting regimes. For an observation of the brightest [Oii]emitters, a moderate resolution is sufficient, whereas for a fainter survey, the highest the resolution the best. Secondly, I estimated the linear galaxy bias of the selections discussed before and I find they are highly biased. On one hand, this is great news for the observers, as the time required to observed at a given signal to noise in the power spectrum decreases with the square of the bias. On the other hand, it constitutes a new challenge for reconstruction algorithms and the making of mock catalogs. The work in progress described in the last chapter shows I am starting to try and handle these questions in a robust manner

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Graef, Leila Lobato. "Cenários unificados para a expansão acelerada do Universo". Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-18082015-112701/.

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Nos encontramos atualmente em um momento histórico privilegiado para a cosmologia. Na última década, o grande progresso das observações astronô- micas permitiu que diversos modelos cosmológicos pudessem ser testados com grande precisão. Com uma série de resultados observacionais sendo lançados, obtivemos informações valiosas sobre a expansão acelerada do universo primitivo e a expansão acelerada atual. Em sua essência, tais esforços observacionais buscam esclarecer algumas das questões mais fundamentais da cosmologia moderna, como a compreensão do mecanismo responsável pela aceleração do universo. Muitas perguntas estão associadas à tal questão, entre elas podemos citar: (i) Qual a natureza da substância, ou qual a origem do fenômeno, que está atualmente acelerando a expansão do universo? (ii) Por qual razão esta expansão acelerada iniciou recentemente (nos últimos 5-8 bilhões de anos), e não no passado distante ou no futuro remoto? (iii) Qual a variante inflacionária que operou no universo primitivo e qual sua conexão (se existe alguma) com o atual estágio acelerado do universo? Em nossa compreensão, as indagações acima fazem parte dos maiores problemas da cosmologia atual. A ampla abrangência de tais questões significa que avanços em qualquer uma delas terá implicações teóricas e observacionais em outras áreas envolvendo a interface formada pela Astronomia, Cosmologia e Física de Partículas. As três questões acima estão diretamente conectadas com os objetivos do presente trabalho. Acreditamos também que seu estudo pode lançar alguma luz e melhorar nossa compreensão sobre questões mais fundamentais da física. Neste contexto, analisamos diferentes modelos cosmológicos para a acelera- ção do universo à luz dos mais recentes dados observacionais de supernovas, radiação cósmica de fundo e oscilações acústicas de bárions. Propomos, aqui, alternativas ao Modelo Padrão da Cosmologia, ao mostrar que diversos fenômenos físicos podem estar associados à expansão do universo, gerando a aceleração observada sem a necessidade de se introduzir componentes desconhecidas no universo além da matéria escura. Além de desenvolver uma revisão crítica do Modelo Padrão, discutimos nesta tese especialmente três modelos para a expansão acelerada do universo. O primeiro deles considera a aceleração cósmica como sendo efeito da criação quântica de partículas de matéria escura, ou radiação, às custas do campo gravitacional variando continuamente com a expansão do universo. O segundo modelo considera o processo de viscosidade volumar no fluido cosmológico como sendo responsável pela aceleração. Esta viscosidade volumar se deve à perda de equilíbrio termodinâmico durante a expansão do fluido. O terceiro modelo, o modelo de decaimento do vácuo, considera como responsá- vel pela aceleração uma energia do vácuo que decai nas outras componentes cósmicas continuamente ao longo do tempo. Analisamos as relações existentes entre estes três modelos, além do Modelo Padrão, e as condições sob as quais os mesmos fornecem uma dinâmica equivalente para o universo. Também obtemos interessantes vínculos para os parâmetros destes modelos ao fazermos, além de uma análise observacional, uma análise teórica baseada na dinâmica e na termodinâmica associada a cada cenário. Sugerimos que estes cenários são capazes de aliviar diversos problemas conceituais do Modelo Padrão da Cosmologia. Numa segunda etapa, mostramos que os processos físicos descritos acima podem ser responsáveis tanto pela aceleração cósmica atual, quanto pela aceleração primordial que se supõe ter ocorrido no universo antigo. Tal abordagem fornece uma descrição unificada para a evolução cosmológica. Acreditamos ser de fundamental importância que o processo que dirigiu a aceleração primordial possa ser relacionado com o mesmo responsável pela atual fase de expansão acelerada do universo. Além disto, é possível que as dificuldades que atingem a interface que une a Relatividade Geral, a Cosmologia e a Teoria Quântica de Campos possam ser amenizadas através de uma melhor compreensão do processo de criação gravitacional de partículas, do decaimento do vácuo e suas conexões com o contexto da inflação primordial. Para comparar e vincular os modelos propostos, analisamos também o processo de formação das estruturas cosmológicas nestes modelos. Introduzimos a teoria de perturbações cosmológicas, primeiramente, através de uma análise do Modelo Padrão. A partir daí, apresentamos uma abordagem mais geral para o tratamento das perturbações chamada teoria de campo efetiva para a inflação. Neste contexto, analisamos quais previsões são obtidas ao se quebrar algumas suposições usualmente assumidas nestes modelos. Por fim, através de uma análise do espectro de potências primordial do modelo de criação gravitacional de partículas e do modelo de viscosidade, mostramos, pela primeira vez, que os mesmos podem ser capazes de gerar um cenário inflacionário para o universo primitivo em concordância com as observações atuais.
We are currently in a privileged moment for cosmology. In the last decade, the great progress of astronomical observations made possible that several cosmological models could be tested with great accuracy. With several observational data being released we obtained valuable information concerning the primordial acceleration of the universe and the recent accelerated expansion. Essentially, these observational efforts aim to clarify some of the most fundamental questions of modern cosmology, which concerns the understanding of the mechanism responsible for the acceleration of the universe. Many questions are related to this issue, among them we can mention: (i) What is the nature of the substance, or what is the origin of the phenomenom, responsible for the acceleration of the expansion? (ii) For which reason the accelerated expansion started recently (within the last 5-8 billion years), and not in the distant past or distant future? (iii) What is the inflationary variant that operated in the early universe, and what is its connection (if there is any) with the current accelerated stage of the universe? In our understanding the above questions are part of the biggest problems in modern cosmology. The interconnection between these issues means that advances in any of them will have theoretical and observational implications in other areas involving the interface formed by Astronomy, Cosmology and Particle Physics. The three questions above are directly connected to the objectives of this work. We also belive that their study can shed some light in our understanding of the remaining issues. In this context, we analyze different cosmological models for the acceleration of the universe in the light of the latest data released from supernovae, cosmic microwave background and baryon acoustic oscillations, comparing the results with the ones concerning the Standard Model of Cosmology. We propose alternatives to the Standard Model of Cosmology, by showing that several physical phenomena can be associated to the expansion of the universe, producing the observed acceleration without the need to introduce unknown components in the universe besides the dark matter. In addition to developing a critical revision of the Standard Model, we discuss in this thesis especially three models for the accelerated expansion of the universe. The first one considers the cosmic acceleration as an effect of the creation of dark matter particles, or radiation, at the expense of the gravitational field varying continuously with the expansion of the universe. The second model considers the process of bulk viscosity in the cosmological fluid as being responsible for the acceleration of the universe. This bulk viscosity is due to the loss of local thermodynamic equilibrium during the expansion of the fluid. The third model, the vacuum decaying model, considers as responsible for the acceleration, a vacuum energy which decays continuously into other cosmological components. We analyze the relations between these three models, and also the Standard Model, and the conditions under which they provide an equivalent dynamic to the universe. We also obtain interesting constraints for the parameters of these models by making, besides an observacional analysis, a theoretical analysis based on the dynamics and thermodynamics associated to each scenario. We will show that these alternative scenarios are able to alleviate several theoretical problems of the Standard Cosmological Model. In a second part, we show that the physical phenomena described above may be responsible for the recent cosmic acceleration, as well as for the primordial acceleration that is supposed to have occurred in the early universe. Such approach provides an unified description for the cosmological history. We belive it is of great importance that the process responsible for inflation can be identified with the one responsible for the current phase of accelerated expansion of the universe. Moreover, it is quite possible that the difficulties concerning the interface connecting General Relativity, Cosmology and Quantum Field Theory can be reduced through a better understanding of the gravitational particle creation process, the decay of the vacuum and its connections with the primordial inflationary context. In order to constrain and compare the models proposed here, we also analyse the process of cosmological structure formation in these models. We firstly introduce the perturbation theory through an analysis of the Standard Model. Then we introduce a more general approach to the treatment of cosmological perturbations which is called effective field theory of inflation. In this context, we analyse which predictions are obtained when we break some of the assumptions usually imposed in these models. Finally, through an analysis of the primordial power spectrum of the gravitational particle creation model and the viscosity model, we show, for the first time, that these models are able to describe an inflationary scenario for the early universe totally in agreement with current observations.

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Ahlström, Kjerrgren Anders. "Galaxies as Clocks and the Universal Expansion". Thesis, KTH, Fysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-294426.

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The Hubble parameter H(z) is a measure of the expansion rate of the universe at redshift z. One method to determine it relies on inferring the slope of the redshift with respect to cosmic time, where galaxy ages can be used as a proxy for the latter. This method is used by Simon et al. in [1], where they present 8 determinations of the Hubble parameter. The results are surprisingly precise given the precision of their data set. Therefore, we reanalyze their data using three methods: chi-square minimization, Monte Carlo sampling, and Gaussian processes. The first two methods show that obtaining 8 independent values of the Hubble parameter yields significantly larger uncertainties than those presented by Simon et al. The last method yields a continuous inference of H(z) with lower uncertainties. However, this is obtained at the cost of having strong correlations, meaning that inferences at a wide range of redshifts provide essentially the same information. Furthermore, we demonstrate that obtaining 8 independent values for the Hubble parameter with the same precision as in [1] requires either significantly increasing the size of the data set, or significantly decreasing the uncertainty in the data. We conclude that their resulting Hubble parameter values can not be derived from the employed data. [1] J. Simon, L. Verde and R. Jimenez, Constraints on the redshift dependence of the dark energy potential, Physical Review D 71, 123001 (2005).
Hubbleparametern H(z) är ett mått på universums expansionshastighet vid rödskift z. En metod som bestämmer parametern bygger på att hitta lutningen av sambandet mellan rödskift och kosmisk tid, där det sistnämnda går att ersätta med galaxåldrar. Denna metod används av Simon et al. i [1], där de presenterar 8 värden av Hubbleparametern. Resultaten är förvånansvärt precisa, med tanke på precisionen i deras data. Vi omanalyserar därför deras data med tre metoder: chi-2-miniminering, Monte Carlo-sampling och Gaussiska processer. De två första metoderna visar att när 8 oberoende värden av Hubbleparametern bestäms fås mycket större osäkerheter än de som presenteras av Simon et al. Den sistnämnda metoden ger en kontinuerlig funktion H(z) med lägre osäkerheter. Priset för detta är dock starka korrelationer, det vill säga att resultat vid många olika rödskift innehåller i princip samma information. Utöver detta visar vi att det krävs antingen en mycket större mängd data eller mycket mindre osäkerheter i datan för att kunna bestämma 8 oberoende värden av Hubbleparametern med samma precision som i [1]. Vi drar slutsatsen att deras värden av Hubbleparametern inte kan fås med den data som använts. [1] J. Simon, L. Verde and R. Jimenez, Constraints on the redshift dependence of the dark energy potential, Physical Review D 71, 123001 (2005).

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France, Lydéric. "Interactions entre processus magmatiques et hydrothermaux aux dorsales océaniques à expansion rapide : implications pour la dynamique de la lentille magmatique axiale". Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2009. http://tel.archives-ouvertes.fr/tel-00448699.

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Ce travail de thèse est basé sur des observations de terrain, sur une étude pétrographique et géochimique des roches formées à la base du complexe filonien dans l'ophiolite d'Oman et au niveau du Site IODP 1256, ainsi que sur une étude expérimentale. De nouvelles contraintes sont apportées sur les processus se produisant à la transition magma / système hydrothermal dans la croute océanique formée au niveau des dorsales à expansion rapide. L'intrusion de gabbros isotropes dans la base du complexe filonien a provoqué son réchauffement et sa recrystallization en « dikes granoblastiques » jusqu'à des températures de 1030°C. Des xénolites de microgabbro à orthopyroxene dérivées des dikes granoblastiques sont souvent observées dans le niveau de gabbros isotropes épais de 100 mètres environ qui est présent à la base du complexe filonien. Ces différentes caractéristiques sont à relier à des migrations verticales vers le haut du sommet de la lentille magmatique supérieure qui est observée aux dorsales rapides. Les nombreuses évidences d'assimilation (xénolites et patchs granoblastiques) dans le niveau des gabbros isotropes appuient l'hypothèse que ce niveau représente la fossilisation de la lentille magmatique supérieure. L'étude expérimentale a consisté à tester l'effet de la fusion partielle du complexe filonien préalablement hydrothermalisé. Les résultats montrent que la fusion commence à 850°C, confirment l'origine résiduelle des dikes granoblastiques et des xénolites associées, et attestent de l'origine anatectique des plagiogranites océaniques qui sont couramment observés à proximité de la base du complexe filonien. La composition en éléments majeurs et traces du liquide anatectique a été déterminée. Ce liquide représente le principal contaminant pour les MORBs primitifs émis au niveau des dorsales rapides. La lentille magmatique supérieure présente au niveau des dorsales médio-océaniques à expansion rapide est ici décrite comme un système dynamique qui peut migrer verticalement, et qui est fossilisée lorsqu'elle se déplace hors axe.

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Italia, James Sebastian. "Development and Applications of Universal Genetic Code Expansion Platforms:". Thesis, Boston College, 2019. http://hdl.handle.net/2345/bc-ir:108354.

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Thesis advisor: Abhishek Chatterjee
The emergence of genetic code expansion (GCE) technology, which enables sitespecific incorporation of unnatural amino acids (UAAs) into proteins, has facilitated powerful new ways to probe and engineer protein structure and function. Using engineered orthogonal tRNA/aminoacyl-tRNA synthetase (aaRS) pairs that suppress repurposed nonsense codons, a variety of structurally diverse UAAs have been incorporated into proteins in living cells. This technology offers tremendous potential for deciphering the complex biology of eukaryotes, but its scope in eukaryotic systems remains restricted due to several technical limitations. For example, development of the engineered tRNA/aaRS pairs for eukaryotic GCE traditionally relied on a eukaryotic cell-based directed evolution system, which are significantly less efficient relative to bacteria-based engineering platforms. The work described in this thesis establishes a new paradigm in GCE through the development of a novel class of universal tRNA/aaRS pairs, which can be used for ncAA incorporation in both E. coli and eukaryotes. We achieve this by developing engineered strains of E. coli, where one of its endogenous tRNA/aaRS pair is functionally replaced with an evolutionarily distant counterpart. The liberated pair can then be used for GCE in the resulting altered translational machinery (ATM) strain, as well as any eukaryote. Using this strategy, we have been able to genetically encode new bioconjugation chemistries, post-translational modifications, and facilitate the incorporation of multiple, distinct ncAAs into a single protein. The ATM technology holds enormous promise for significantly expanding the scope of the GCE technology in both bacteria and eukaryotes
Thesis (PhD) — Boston College, 2019
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry

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Rauzy, Stéphane. "Etude de la distribution et de la cinématique des galaxies dans l'univers". Aix-Marseille 2, 1993. http://www.theses.fr/1993AIX22010.

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Cette thèse est composée de cinq parties : A) Je définis le champ des vitesses propres des galaxies. B) Je présente un formalisme statistique rigoureux permettant l'obtention de la vitesses radiale propre d'une galaxie à partir des données observationnelles. C) Je montre que l'évaluation du tenseur de corrélation des vitesses est actuellement impossible. D) Je présente des tests géométriques mettant en évidence la présence du grand attracteur. E) J'introduis une méthode à base d'ondelettes permettant la reconstruction du champ des vitesses propres total à partir de sa composante radiale seulement

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Solís, Benites Mario Florencio. "La métrica de McVittie: agujeros negros en el universo en expansión". Bachelor's thesis, Universidad Nacional Mayor de San Marcos, 2017. https://hdl.handle.net/20.500.12672/7645.

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Estudia la métrica de McVittie para el caso plano. Eso requiere de un desarrollo de la relatividad general y la cosmología. Estudia los agujeros negros, en donde deduce la métrica planteada por Karl Schwarzschidl, bajos las mismas consideraciones, métrica estática y con un parámetro distinto a las coordenadas que es la masa; también, realiza una transformación de coordenadas que conduce a versión isotrópica de la métrica de Schwarzschild.
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Lorenc, Jan. "Environment for storytelling : an expansion of Wren's nest utilizing universal design". Thesis, Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/22406.

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Alimi, Jean-Michel. "Contributions instabilité gravitationnelle dans un univers en expansion et formation des grandes structures /". Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37602227f.

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Campbell, Mariam. "Cyclic universes & direct detection of cosmic expansion by holonomy in the McVittie spacetime". Master's thesis, Faculty of Science, 2019. http://hdl.handle.net/11427/31091.

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This dissertation consists of two parts. They are separate ideas, but both fall into the context of General Relativity using dynamical systems. Part one is titled Cyclic Universes. It is shown that a Friedmann model with positive spatial sections and a decaying dark energy term admits cyclic solutions which is shown graphically by the use of phase planes. Coupling the modified Friedmann model to a scalar field model with cross-sectional terms in order to model the reheating phase in the early universe, it is found that there is a violation of the energy condition, i.e. when the universe is in the contracting phase and re-collapses again. We suspect that the cause for this violation is due to the asymmetry of the solution of w together with the cross-sectional terms at the bounce preceding slow-roll inflation. Part two is titled Thought Experiment to Directly Detect Cosmic Expansion by Holonomy. Two thought experiments are proposed to directly measure the expansion of the universe by the parallel transfer of a vector around a closed loop in a curved spacetime. Generally, expansion would cause a measurable deficit angle between the vector’s initial and final positions. Using the McVittie spacetime (which describes a spherically symmetric object in an expanding universe) as a backdrop to perform these experiments it is shown that the expansion of the universe can be directly detected by measuring changes in the components of a gyroscopic spin axis. We find these changes to be small but large enough (∆S ∼ 10−7 ) to be measured if the McVittie spacetime were a representation of our universe.

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Youssef, Ahmed. "Effets quantiques dans des modèles d'univers en expansion". Paris 7, 2011. http://www.theses.fr/2011PA077097.

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Les univers en expansion sont l'objet central de cette thèse. Tout d'abord, nous étudions la théorie quantique des champs dans le prototype de ces univers, à savoir l'espace-temps de de Sitter. En effet, les ( de la théorie des champs dans cet espace souffrent de toutes sortes de divergences infrarouges. Comment calculer correctement en présence de ces divergences et quel est leur sens ultime sont des questions centrales pour les cosmologistes. Nous étudions cette question en détail dans le cas de l'électrodynamique quantique. Nous étudions ensuite plusieurs aspects des théories de modification de la relativité générale. La principale motivation de ces théories est qu'élit donnent naturellement lieu à une phase d'expansion, soit dans l'univers primitif (inflation), soit aujourd'hui (énergie noire). Un trait caractéristique ces modèles est qu'ils conduisent à des théories avec des dérivées d'ordre supérieur, ce qui complique grandement leur analyse. Nous examinons l'équivalence de différentes formulations Hamiltoniennes de ces théories. Nous analysons ensuite les perturbations cosmologiques dans le cas d' modèle particulier, à savoir la gravité de Weyl, à nouveau dans le contexte des univers en expansion
Expanding spacetimes are the central object of this thesis. First, we investigate quantum field theory (QFT) in the prototype of these spacetimes, the de Sitter spacetime. In particular, QFT calculations in Sitter space are plagued by ail sorts of infrared divergences. How to correctly compute in presence of these divergences and vvhat they ultimately are central questions to cosmologists. We study this issue in detail for free electrodynamics. We then study several aspects of higher-derivatives theories of gravity whose major motivation is that they give rise quite naturally to an examine phase either in the early universe (inflation), either today (dark energy). We examine the equivalence of different Hamiltonian formulations of the theories. We also analyze cosmological perturbations of a special higher-derivative theory of gravity, namely Weyl gravity, again in the context expanding spacetimes

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Ceccolini, David. "Relativité d'échelle appliquée à la formation et l'évolution des structures dans un univers en expansion". Paris 11, 2009. http://www.theses.fr/2009PA112038.

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L’objet de ce travail est l’étude de la formation des structures dans un univers en expansion sous l’hypothèse que l’espace-temps est non seulement courbe, mais aussi fractal. Cette fractalité implique une dépendance d’échelle explicite des quantités physiques, décrite dans le cadre de la théorie de la relativité d’échelle. L’équation des géodésiques s’intègre alors en une équation du type Schrödinger, mais peut aussi prendre une forme d’équations de la mécanique des fluides comprenant un terme de potentiel « quantique ». Cette dernière forme est donc semblable à celle utilisée dans l’approche standard mais inclue une énergie potentielle supplémentaire qui joue un rôle auto-organisateur et pourrait contribuer à l’interprétation des effets habituellement attribués à la « matière noire » non baryonique. Le but spécifique de cette thèse est la généralisation de cette approche au cas dépendant du temps, d’un fond cosmologique en expansion. Une méthode progressive a été adoptée : (A) En coordonnées propres le potentiel du fond est celui d’un oscillateur harmonique. On analyse les cas suivants (A1) potentiel du fond cosmologique seul, dépendance du temps négligée ; (A2) potentiel du fond seul, dépendance en fonction du temps de sa densité moyenne prise en compte, calculs perturbatifs ; (A3) potentiel du font et potentiel d’autogravitation de la structure en formation tous deux pris en compte. (B) En coordonnées comobiles, la dépendance temporelle et le potentiel du fond cosmologique sont pris en compte à travers le facteur d’échelle a (t), suivant eux étapes : (B1) fond cosmologique seul ; (B2) prise en compte du fond cosmologique et le l’autogravitation de la structure
The present work studies the formation of structures in an expanding universe under the hypothesis that space-time in not only curved, but also fractal. This fractality involves an explicit scale dependence of physical quantities, described in the framework of the scale relativity theory. The geodesic equation can then be integrated in terms of a Schrödinger-type equation, and it can also be given the form of fluid mechanics equations including a “ quantum potential” term. This last form is therefore similar to the equations used in the standard approach, but it includes an additional potential energy which plays a self-organizing role and could contribute to the interpretation of the effects usually attributed to non-baryonic “dark matter”. The specific goal of this thesis is the generalization of this approach to the time-dependent case of an expanding cosmological background. To this purpose, a progressive method has been adopted. (A) In proper coordinates, the background potential is an harmonic oscillator potential. The following cases have been analysed : (A1) background potential only, time dependence neglected ; (A2) background potential only, time dependence of mean density accounted for, perturbative approach ; (A3) background potential and gravitational self-potential of the structure in formation both taken into account. (B) In comoving coordinates, the time dependence and the cosmological background potential are taken into account through the scale factor a (t), following two steps : (B1) cosmological background only ; (B2) account of cosmological background and of self-gravitation of the structure

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Villegas, Silva Fulgencio. "El Universo de MCVITTIE y algunas soluciones cosmológicas". Doctoral thesis, Universidad Nacional Mayor de San Marcos, 2019. https://hdl.handle.net/20.500.12672/10730.

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Busca soluciones exactas para las ecuaciones de Einstein se ha desenvuelto en dos direcciones diferentes por un lado, el estudio de objetos masivos aislados cuyo campo gravitacional externo es modelado por soluciones asintóticamente planas (métrica de Schwarzschikl); y por otro lado, el estudio a gran escala del universo, en forma global, para predecir su evolución, origen y su destino final (métrica FLRW). Pero hay un tercer camino que trata de mantener estos dos aspectos juntos, se trata de la métrica de McVittie, la cual nos presenta la posibilidad de estudiar los sistemas locales influenciados por la evolución a gran escala del espacio en el que están inmersos. Motivados por este enfoque, realizamos un estudio de la métrica de McVittie en dos etapas. En la primera etapa, analizamos el espacio-tiempo de McVittie para una partícula cargada y a partir de ello, mediante una construcción matemática adecuada, introducimos la constante de Hubble. Posteriormente haciendo uso de las ecuaciones de campo de Einstein, se resuelve la ecuación de McVittie cargada con constante cosmológica negativa. En la segunda etapa, partimos del agujero de gusano atravesable de MorrisThorne, la función de desplazamiento al rojo se hace nula y se realiza un cambio de variable adecuado para la función de forma, se construye una métrica para un agujero de gusano atravesable en el universo de FLRW; posteriormente, se analiza el caso de un agujero de gusano más general, se utiliza la métrica de McVittie, donde el agujero de gusano está modelado por una delgada capa esférica que acrecenta el fluido de quinta esencia, finalmente, se encuentra la evuación dinámica de dicha capa delgada y el radio comoving de la misma.
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Beck, Arnaud. "Simulation N-Corps d'un plasma". Phd thesis, Observatoire de Paris, 2008. http://tel.archives-ouvertes.fr/tel-00359057.

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La simulation N-Corps d'un plasma consiste à calculer l'interaction coulombienne mutuelle entre N particules chargées. Nous avons adapté un algorithme N-Corps de type ``code en arbre'', utilisé avec succès dans le cas gravitationnel, pour la simulation de plasmas. Pour l'instant, nous avons trouvé deux champs d'applications pour lesquels cette technique est particulièrement bien adaptée.

Tout d'abord les problèmes d'expansion de plasma dans le vide. Ce genre de simulation fait coexister des densités d'ordres de grandeur très différents. Certaines zones peuvent avoir un comportement hydrodynamique pendant que d'autres sont peuplées de particules avec des trajectoires balistiques car trop énergétiques. Les protons, notamment, peuvent ainsi être accélérés à des vitesses requises pour la fusion. Ce type de problème, faisant intervenir une interface plasma-vide, est pratiquement impossible à étudier à l'aide des techniques de simulation courantes (e.g. codes MHD, Vlasov, Fokker-Planck, ...).

L'autre champ d'application est celui de la simulation des plasmas modérément ou fortement couplés qui concerne de nombreux plasmas de laboratoire, mais également des plasmas astrophysiques, tels, par exemple, la zone convective du Soleil. Dans les plasmas dits couplés, les collisions ``binaires proches'' entre charges ne peuvent pas être négligées. Or, les modèles numériques de type Fokker-Planck, très majoritairement utilisés pour simuler des plasmas faiblement collisionnels, n'en tiennent pas compte ce qui les rends inadéquats à ce type de plasma. La technique N-Corps, quant à elle, gère chaque particule individuellement et peut très bien décrire précisément les trajectoires de particules subissant ce genre de déviation violente.

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Silva, Paulo Michel Longo Tavares da. "Uma descrição da expansão e aceleração do universo no contexto das teorias f(R)". Universidade do Estado de Santa Catarina, 2012. http://tede.udesc.br/handle/handle/1965.

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This work reviews concisely some of the theoretical attempts to explain the recently observed acceleration of the universe. Emphasis is put on the so-called theories f(R) which involve invariant modi.cations of the Einstein-Hilbert Lagrangian density. The pertinent .eld equations are derived from three distinct formalisms which are known in the literature as the metric formalism, the Palatini formalism and the a¢ ne formalism. For the case of the metric and Palatini formalisms, we carry out some interesting calculations and show the corresponding versions of the Friedmann equations. In addition, we present a minimally coupled Friedmann-Maxwell-f(R) model which may give a cosmological equation of state for w that agrees with available measurements of the red-shift of Ia supernovae.
Diante das observações experimentais da expansão cósmica acelerada, diversos - modelos teóricos surgiram para explicar a aceleração do Universo. Neste trabalho revisamos modelos tais como a constante cosmológica e quintessência, a qual é modelada por um campo escalar. O contexto aqui apresentado foi elaborado a partir das teorias modificadas da gravitação, também conhecidas como teorias f(R). Tal modelo é considerado uma generalização da ação de Einstein-Hilbert onde termos invariantes de curvatura podem descrever um regime acelerado para o universo. As equações de campo podem ser obtidas a partir de três formalismos distintos, a saber, formalismo métrico, Palatini e métrico-afim. Realizamos algumas manipulações algébricas para esses formalismos, bem como a apresentação das equações de Friedmann generalizadas para o formalismo métrico e Palatini. Também apresentamos um modelo no formalismo métrico com um campo de Maxwell acoplado minimamente. As equações de Friedmann-Maxwell-f(R), as quais dependem da forma funcional de f(R) como também do campo Fµv, permitem que uma equação de estado para w pode ser ajustada em concordância com as medidas do red-shift de supernovas IA.

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Tumpkin, Mary A. "An expansion strategy for the universal foundation for better living based on a Jamaican model". Theological Research Exchange Network (TREN), access this title online, 1998. http://dx.doi.org/10.2986/tren.108-0010.

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Teston, Felipe. "Instabilidade gravitacional para um universo estático e em expansão sob influência de termos dissipativos". reponame:Repositório Institucional da UFPR, 2017. http://hdl.handle.net/1884/49566.

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Orientador: Prof. Dr. Gilberto Medeiros Kremer
Dissertação (mestrado) - Universidade Federal do Paraná, Setor de Ciências Exatas, Programa de Pós-Graduação em Física. Defesa: Curitiba, 22/02/2017
Inclui referências : f. 72-74
Resumo: Com o início da fase da recombinação e por consequência o desacoplamento dos fótons da matéria, as primeiras estruturas passaram a ser formadas no Universo. A Cosmologia tenta, desde os séculos passados, determinar relações matemáticas que descrevem o crescimento destas estruturas para pequenas e grandes escalas. Jeans inaugurou o estudo da formação de estruturas em 1902 levando em conta a geração de atuações e a evolução dos modos perturbados para diferentes eras do Universo. Com seu trabalho, Jeans introduziu uma constante que hoje _e conhecida como comprimento de Jeans que descreve a condição mínima, em termos de comprimento de onda, para que uma estrutura cósmica seja formada. Neste trabalho iremos fazer uso das equações de uido da Cosmologia Newtoniana para estudar pequenas utuações de densidade e temperatura em um Universo estático e em expansão.
Abstract: After the decoupling of photons from matter, the process of structure formation was ignited, giving origin to the large scale structure of the Universe as is known today. One of the main goal of the XIX century cosmology was to establish a fundamental framework to describe the growth of small ripples and the mechanism behind the generation of such structures within small and large cosmological scales. The seminal work of Jeans in 1902 gave the _rst approach to deal with structures formation process by taking into account the physical origin of small uctuation, along with the evolution of the perturbed modes during di_erent kinds of cosmological eras. In the aforesaid work, Jeans introduced a characteristic scale, known as Jeans scale, which indicates the minimal condition which assures the formation of cosmic structures. In the present thesis, we are going to make use of such formalism within the context of Newtonian cosmology with a cosmic uid as the main source. Our aim is to examine the small uctuations of matter density along with small uctuation of temperature for a static universe and for an expanding universe.

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Inazumi, Mitsue. "Universal jurisdiction in modern international law: expansion of national jurisdiction for prosecuting serious crimes under international law /". Antwerpen [u.a.] : Intersentia, 2005. http://www.gbv.de/dms/spk/sbb/recht/toc/490917232.pdf.

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Stratonovitch, Jean. "Eléments de réponse au sixième problème de Hilbert (axiomatiser la physique) dans le domaine de la cinématique : prolongement vers une dynamique. Illusions d'optique dans un univers de Bruno. Statut théorique de la lumière dans la cinématique". Université Louis Pasteur (Strasbourg) (1971-2008), 2001. http://www.theses.fr/2001STR13100.

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Bowane, Adrien Gyato. "IGREJA UNIVERSAL DO REINO DE DEUS NA ÁFRICA SUBSAARIANA: IMPLANTAÇÃO, EXPANSÃO E TRANSNACIONALIZAÇÃO". Universidade Metodista de São Paulo, 2014. http://tede.metodista.br/jspui/handle/tede/340.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico
The purpose of this paper is to show the implementation strategies and the expansion of the Universal Church of the Kingdom of God (UCKG) in sub-Saharan Africa, while taking into account the rapid growth of Pentecostalism in the world and the context of religious trans-nationalization. The UCKG is a Brazilian Pentecostal Church that emerged in 1977 and expanded into many countries worldwide. It is present in 39 countries in sub-Saharan Africa concentrating mostly in large cities. Several factors prove its growth and expansion in Africa, among other factors syncretism, i.e., the ability to adapt to African culture. The other factors are: social visibility (especially through the use of media and social assistance), the political secrecy, the practice of exorcism, prosperity discourses, the friendship and partner-ship with African governments, their anti-ecumenical attitude and the adoption of an Episcopal organization. This paper brings some discussions regarding Pentecostalism and neo-Pentecostalism in Sub-Saharan Africa, African Independent Churches (AIC) and the presence of Christianity in Africa since the very beginning.
Esse trabalho trata das estratégias de implantação e expansão da Igreja Universal do Reino de Deus (IURD) na África Subsaariana, tendo conta de crescimento acelerado do pentecostalismo no mundo e no contexto da transnacionalização religiosa. A IURD é uma Igreja neopentecostal brasileira que surgiu em 1977 e se expandiu em vários países do mundo. Ela está presente em 39 países da África subsaariana e se concentra nas grandes cidades. Vários fatores explicam o seu crescimento e expansão no continente africano, entre os quais o sincretismo, isto é, a capacidade de se adaptar à cultura africana. Outros fatores são: a visibilidade social (especialmente no uso da mídia e a assistência social), a política do segredo, a prática de exorcismo, o discurso da prosperidade, a relação de amizade e de parceria com governos africanos, a sua atitude anti-ecumênica e a adoção de uma organização episcopal. Aborda-se também nesse trabalho, o pentecostalismo e o neopentecostalismo na África, as Igrejas Independentes Africanas (IIA) e a presença do Cristianismo no continente africano desde os primórdios.

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Escalera, Eric. "Etude dynamique et structurale des amas de galaxies : une utilisation de la Transformée en Ondelettes". Toulouse 3, 1992. http://www.theses.fr/1992TOU30258.

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Le travail presente ici s'inscrit dans le cadre de la recherche de la structure reelle et de la dynamique des amas de galaxies, avec pour toile de fond une approche plus realiste de la masse (et de la masse cachee) de ces systemes et le choix des scenarios de formation des grandes structures (modeles cosmologiques). Cela revient, a terme, a redefinir ce qu'est un amas de galaxies. Pour cette recherche, nous avons applique une nouvelle methode basee sur la transformee en ondelettes, sur des donnees a 2 dimensions mais aussi a 3 dimensions (vitesses radiales en plus), ce qui est une premiere dans le domaine. Apres avoir teste la methode sur divers modeles et constate l'innovation qu'elle apporte (notamment par son objectivite et par la validite statistique des resultats), nous avons realise l'analyse de trois amas reels: abell 754, abell 151, et coma, pour rencontrer des sous-structures jusque dans le centre de coma. . . Nous presentons egalement les resultats pour six autres amas: perseus, hydra, hercules, abell 2670, abell 3716, et virgo, et nous en discutons les conclusions, notamment par rapport aux travaux anterieurs publies dans la litterature. Les nombreuses irregularites structurales mises en evidence ici contredisent l'hypothese selon laquelle les amas de galaxies seraient des systemes parfaitement reguliers

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Berthonneau, Jérémie. "Le rôle des minéraux argileux dans la dégradation de la pierre : application à la conservation de la "Pierre du Midi" en termes de durabilité et compatibilité des matériaux en oeuvre". Phd thesis, Aix-Marseille Université, 2013. http://tel.archives-ouvertes.fr/tel-00958572.

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De par l'étendue de leur répartition géographique et la facilité de leur extraction, les molasses d'âge miocène du bassin rhodanien ont été largement exploitées par l'homme comme pierre de construction depuis le début de l'ère chrétienne. Le patrimoine bâti provençal érigé à l'aide de ce matériau, connu sous le nom de " Pierre du Midi ", et exposé aux intempéries depuis plus de cinq cents ans présente cependant un certain nombre de morphologies de dégradations. Parmi ces dégradations, la desquamation en plaques a la particularité de se développer en dehors des zones de remontées capillaires ainsi qu'en l'absence de sels solubles, de sollicitation mécanique, de pollution atmosphérique ou de colonisation biologique. Ce phénomène est donc induit par les propriétés intrinsèques du matériau et son comportement vis-à-vis des conditions environnementales. L'objectif de ce travail de recherche est d'établir le rôle joué par les minéraux argileux dans ce phénomène de dégradation spécifique. Une étude de terrain a pu mettre en exergue que le degré de desquamation en plaques observable sur des monuments de périodes de construction équivalentes est variable suivant l'origine des assises. A l'issue de cette reconnaissance, neuf échantillons représentatifs de la variabilité du degré de desquamation en plaques ont été prélevés en carrières. Une étude conventionnelle sur les caractéristiques pétrographiques et la composition minéralogique de ces types de " Pierre du Midi " a tout d'abord été conduite. Par la suite, une définition précise du cortège de minéraux argileux a été menée par le biais d'une approche méthodologique originale. Cette dernière combine la caractérisation cristallochimique au MET-EDS à la simulation des raies 00ℓ de diffraction des rayons X. Cette méthode a permis de déterminer les quantités de chacune des phases de phyllosilicate composant les différents cortèges. Le lien entre la quantité de feuillets de phyllosilicates expansifs et le degré de desquamation en plaques a pu, de ce fait, être mis en évidence. Après avoir déterminé les propriétés de stockage et de transfert des fluides des différents types de pierre, leur comportement hydromécanique a été évalué. L'ensemble de ces propriétés pétrophysiques a permis de mettre en relief la forte hétérogénéité du matériau à l'étude. Les indices de durabilité calculés à partir de ces résultats manquent cependant de pertinence quant à la prédiction du phénomène de desquamation en plaques. Après une analyse statistique (ACP) des données expérimentales, la meilleure interprétation suggère que ce phénomène soit déclenché par l'interaction entre les feuillets de phyllosilicates expansifs et les molécules d'eau. Cette interaction se manifeste par le comportement hydromécanique des pierres qui entraîne leur dégradation. Ce dernier est largement contrôlé par les propriétés physiques de stockage et de transfert des fluides qui conditionnent l'accommodation des déformations au niveau macroscopique.

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Zoubian, Julien. "Observations cosmologiques avec un télescope grand champ spatial : Simulations pixels du spectromètre sans fente d'EUCLID". Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4821/document.

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Les observations des supernovae, du fond diffus cosmologique, et plus récemment la mesure des oscillations acoustiques des baryons et des effets de lentilles gravitationnelles faibles, favorisent le modèle cosmologique LambdaCDM pour lequel l'expansion de l'Univers est actuellement en accélération. Ce modèle fait appel à deux composants insaisissables, la matière sombre et l'énergie sombre. Deux approches semblent particulièrement prometteuses pour sonder à la fois la géométrie de l'Univers et la croissance des structures de matière noire, l'analyse des distorsions faibles des galaxies lointaines par cisaillement gravitationnel et l'étude des oscillations acoustiques des baryons. Ces deux méthodes demandent de très grands relevés du ciel, de plusieurs milliers de degrés carrés, en imagerie et en spectroscopie. Dans le contexte du relevé spectroscopique de la mission spatiale EUCLID, dédiée à l'étude des composantes sombres de l'univers, j'ai réalisé des simulations pixels permettant l'analyse des performances instrumentales. La méthode proposée peut se résumer en trois étapes. La première étape est de simuler les observables, c'est à dire principalement les sources du ciel. Pour cela j'ai développé une nouvelle méthode, adapté à la spectroscopie, qui permet d'imiter un relevé existant, en s'assurant que la distribution des propriétés spectrales des galaxies soit représentative des observations actuelles, en particulier la distribution des raies d'émission. La seconde étape est de simuler l'instrument et de produire des images équivalentes aux images réelles attendues
The observations of the supernovae, the cosmic microwave background, and more recently the measurement of baryon acoustic oscillations and the weak lensing effects, converge to a LambdaCDM model, with an accelerating expansion of the today Universe. This model need two dark components to fit the observations, the dark matter and the dark energy. Two approaches seem particularly promising to measure both geometry of the Universe and growth of dark matter structures, the analysis of the weak distortions of distant galaxies by gravitational lensing and the study of the baryon acoustic oscillations. Both methods required a very large sky surveys of several thousand square degrees. In the context of the spectroscopic survey of the space mission EUCLID, dedicated to the study of the dark side of the universe, I developed a pixel simulation tool for analyzing instrumental performances. The proposed method can be summarized in three steps.The first step is to simulate the observables, ie mainly the sources of the sky. I work up a new method, adapted for spectroscopic simulations, which allows to mock an existing survey of galaxies in ensuring that the distribution of the spectral properties of galaxies are representative of current observations, in particular the distribution of the emission lines. The second step is to simulate the instrument and produce images which are equivalent to the expected real images. Based on the pixel simulator of the HST, I developed a new tool to compute the images of the spectroscopic channel of EUCLID. The new simulator have the particularity to be able to simulate PSF with various energy distributions and detectors which have different pixels

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ALMEIDA, Douglas Monteiro de. "A expans?o universit?ria na Baixada Fluminense: educa??o e desenvolvimento (1998/2010)". Universidade Federal Rural do Rio de Janeiro, 2016. https://tede.ufrrj.br/jspui/handle/jspui/1819.

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CAPES
The relationship between education and development can be treated by different perspectives. Education can be a shuttle of an economic development process as well a fuel toward improvements on both production and living standards. This research has as its starting point the university expansion process in the 2000s. This process of expansion, given the increase in the number of higher education courses in their territory has been analyzed from the speeches (all tied to education theories) used as legitimizing arguments that expansion of higher education. Specifically, we sought to understand what the effects of the implementation of a Federal institution of higher education in the Baixada Fluminense and the new settings or social and economic dynamics of this process. To further elucidate the process was handled the case of the Multidisciplinary Institute of the Federal Rural University of Rio de Janeiro, located in the city of Nova Igua?u, in the Baixada Fluminense.
A rela??o entre educa??o e desenvolvimento pode ser tratada por diferentes ?ticas, tanto a educa??o pode alavancar um processo de desenvolvimento econ?mico como pode ser considerado o que alimenta o avan?o na sociedade atrav?s de melhorias produzidas pela sua popula??o. Esta pesquisa tem como ponto de partida o processo de expans?o universit?ria na d?cada de 2000. Tal processo representou a instala??o e amplia??o de institui??es de ensino superior na Baixada Fluminense. Esse processo de expans?o, dado o aumento no n?mero de cursos de ensino superior no seu territ?rio foi analisado a partir dos discursos (todos atrelados ?s teorias de educa??o) utilizados como argumentos de legitima??o dessa amplia??o do ensino superior. Especificamente, buscou-se compreender quais os efeitos da implanta??o de uma Institui??o Federal de Ensino Superior na Baixada Fluminense e as novas configura??es ou din?micas sociais e econ?micas decorrentes deste processo. Para elucidar melhor o processo foi tratado o caso do Instituto Multidisciplinar da Universidade Federal Rural do Rio de Janeiro, localizado no munic?pio de Nova Igua?u, na Baixada Fluminense.

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Morais, Breytner Ribeiro. "Aceleração e termodinâmica do horizonte aparente da métrica de FLRW no contexto do TEGR". reponame:Repositório Institucional da UnB, 2015. http://repositorio.unb.br/handle/10482/20090.

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Dissertação (mestrado)—Universidade de Brasília, Instituto de Física, Programa de Pós-Graduação em Física, 2015.
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A solução de Friedmann-Lemaître-Robertson-Walker (FLRW) é uma solução exata das equações de Einstein que descreve um modelo de universo isotrópico e homogêneo que pode está expandindo ou contraindo de forma acelerada. Dados observacionais recentes sugerem que o presente universo é aproximadamente plano e que este está expandindo acelerado. Nesta dissertação, no contexto do Teleparallelismo Equivalente à Relatividade Geral (TERG), tentaremos entender a razão pela qual o universo, baseado no modelo de FLRW, está expandindo de forma acelerada. Apresentaremos também uma relação para a primeira lei da termodinâmica para a superfície do horizonte aparente do modelo de FLRW, de onde extrairemos uma expressão para a temperatura no horizonte aparente. ____________________________________________________________________________________ ABSTRACT
The Friedmann-Lemaître-Robertson-Walker (FLRW) solution, is an exact solution of Einstein equations that describes a homogeneous, isotropic model of universe that may be expanding or contracting in an accelerated way. Recent observational data suggests that the present universe is approximately _at and that it is expanding accelerated. In this Dissertation, in the context of the Teleparallelism Equivalent of General Relativity (TEGR), we will try to understand the cause on which the universe, based in the FLRW model, is expanding in an accelerated way. We also present a relation to the _rst law of thermodynamics to the apparent horizon of the FLRW model, and from this relation we will obtain a expression to the temperature at the apparent horizon.

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Lombard, Alix. "Les variations actuelles du niveau de la mer : Observations et causes". Phd thesis, Université Paul Sabatier - Toulouse III, 2005. http://tel.archives-ouvertes.fr/tel-00079969.

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Alors que depuis un peu plus de 2000 ans, le niveau moyen de la mer a peu varié, ce niveau s'est élevé d'environ 2 mm/an au cours du 20ème siècle. Cette hausse soudaine est attribuée au réchauffement climatique d'origine anthropique enregistré depuis plusieurs décennies. Depuis une douzaine d'années, on mesure de façon globale et précise les variations du niveau de la mer grâce aux satellites altimétriques Topex/Poseidon et Jason-1. Ces observations indiquent une hausse moyenne globale d'environ 3 mm/an depuis 1993, valeur sensiblement plus grande que celle des dernières décennies.
Diverses observations disponibles depuis peu nous ont permis de quantifier les contributions des divers facteurs climatiques à la hausse observée du niveau de la mer : expansion thermique de la mer due au réchauffement des océans, fonte des glaciers de montagne et des calottes polaires, apport d'eau des réservoirs continentaux. Le bilan de ces nouvelles observations nous permet d'expliquer en partie la hausse observée du niveau de la mer. En particulier, nous montrons que l'expansion thermique des océans n'explique que 25% de la hausse séculaire du niveau de la mer enregistrée par les marégraphes depuis 50 ans, tandis qu'elle contribue à la hauteur de 50% à la montée du niveau marin au cours de la dernière décennie. Parallèlement, des études récentes estiment que la fonte des glaciers de montagne et des calottes polaires pourraient contribuer pour environ 1 mm/an à l'élévation du niveau de la mer au cours de la dernière décennie.
De plus, la forte variabilité régionale des vitesses d'évolution du niveau de la mer révélée par les observations altimétriques de Topex/Poseidon résulte en grande partie de l'expansion thermique. Nous mettons également en lumière l'importante variabilité spatio-temporelle décennale de l'expansion thermique des océans au cours des 50 dernières années, qui semble dominée par les fluctuations naturelles du climat. De plus nous posons pour la première fois la question du lien qui existe entre les fluctuations décennales de l'expansion thermique des océans et la contribution climatique des eaux continentales au niveau de la mer. Enfin, une analyse préliminaire des observations gravimétriques de la mission spatiale GRACE sur les océans nous permet d'évaluer les variations saisonnières du niveau moyen de la mer liées aux variations du bilan de masse d'eau des océans.

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Araújo, Bruno Gomes de. "A expansão regional das redes de poder da Igreja Universal do Reino de Deus no Brasil". PROGRAMA DE PÓS-GRADUAÇÃO EM GEOGRAFIA, 2018. https://repositorio.ufrn.br/jspui/handle/123456789/25610.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O pentecostalismo se tornou o fenômeno religioso mais significativo no Brasil da segunda metade dos séculos XX e início do XXI, reverberando em sua estrutura social, cultural, política e econômica. A Igreja Universal do Reino de Deus (IURD), fundada em 1977, pelo bispo Edir Macêdo, apesar de não ser pioneira foi a principal protagonista nesse processo, produzindo uma nova dinâmica de expansão baseada no desenvolvimento e integração de múltiplas redes de poder que ultrapassaram o campo religioso convencional ao conquistar espaços nos circuitos superiores de produção da economia urbana, e em particular na indústria midiática, sempre interagindo fortemente com a reconfiguração regional brasileira posta em cada período. Vislumbrando as condicionantes espaciais da expansão e capilarização das redes iurdianas de poder, o núcleo central da tese buscou evidenciar que o desenvolvimento institucional e territorial da IURD de modo a completar sua universalização pelo território brasileiro, foi estruturado a partir de múltiplas estratégias, todas adequadas às condições geográficas específicas encontradas pela cúpula da Igreja (sobretudo a expansão das redes técnicas de informação e de circulação no território, e a normatização do território). Em outras palavras, a presente tese esteve sempre atenta ao ritmo das mudanças sociais e técnicas que marcaram a evolução do processo de integração diferenciada das macrorregiões brasileiras, particularmente no período de 1990 a 2010, quando a última fronteira ao evangelismo iurdiano é cruzada com sua tardia, mas intensa presença na Região Norte. A dispersão regional das redes iurdianas foi desvendada nos diferentes arranjos infraestruturais apresentados, entre eles, as redes de templos, de emissoras de radiodifusão e teledifusão, e a estrutura político partidária. Todos esses subsistemas possibilitaram a superação das contingências impostas pelas heterogeneidades do desenvolvimento socioeconômico nas regiões brasileiras, facilitando, assim, o controle e mobilização do fluxo de pessoas e de informação, bem como, o acesso às áreas mais remotas do território brasileiro.
Pentecostalism became the most significant religious phenomenon in Brazil of the second half of the twentieth and early twenty-first centuries, reverberating in its structure social, cultural, political and economic. The Universal Church of the Kingdom of God (IURD), founded in 1977, by Bishop Edir Macêdo, although not a pioneer, was the main protagonist in this process, producing a new dynamic of expansion based on in the development and integration of multiple networks of power that have conventional religious field by conquering spaces in the upper production of the urban economy, and in particular in the media industry, interacting strongly with the Brazilian regional reconfiguration put in each period. Glimpsing the spatial constraints of expansion and capillarization the core of the thesis sought to show that the institutional and territorial development of the IURD in order to complete its the Brazilian territory, was structured adapted to the specific geographical conditions by the leadership of the Church (especially the expansion of technical information and circulation in the territory, and the normalization of the territory). In other words, the This thesis has always been attentive to the pace of social and technical marked the evolution of the differentiated integration process of the macro-regions Brazil, particularly in the period from 1990 to 2010, when the last frontier evangelism is crossed with its late, but intense presence in the North. The regional dispersion of the iurdianas networks was unveiled in the different infrastructural arrangements presented, among them, the networks of temples, broadcasters, and political party structure. All these subsystems made it possible to overcome the contingencies imposed by heterogeneities of socioeconomic development in the Brazilian regions, thus facilitating the control and mobilization of the flow of people and information, as well as access to the most remote areas of the Brazilian territory.

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Cardoso, Andréa de Matos. "A aquisição de estratégias de escrita através do universo da narrativa investigativa de Agatha Christie". Universidade Federal de Juiz de Fora (UFJF), 2018. https://repositorio.ufjf.br/jspui/handle/ufjf/7011.

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É comum ouvir hoje, ao se abordarem questões de leitura e produção textual na sala de aula de Ensino Fundamental, que o aluno deve ter contato com um leque variado de textos, para que possa ampliar seus conhecimentos sobre a língua, utilizando-a de forma a atingir os objetivos desejados. Neste sentido, é indispensável que se explorem os mais diversos gêneros textuais, independentemente de que tipologia textual nele predomine. Contudo, pelo menos na minha prática, percebo uma tendência em se privilegiar, sobretudo com o trabalho de escrita, quando focamos texto de opinião, diálogo argumentativo, resenha crítica, dentre outros que têm o tipo textual predominantemente dissertativo-argumentativo. Outro fato que sempre me chamou atenção enquanto professora do Ensino Fundamental II, é que as narrativas que envolvem a perspectiva investigativa, tais como as narrativas policiais, agradam aos alunos bastante. Em geral, eles vivenciam essas narrativas em filmes e, em sua grande maioria, em séries, como Dexter e 24 horas, por exemplo. Nesse sentido, concebemos a seguinte hipótese investigativa: tendo em vista que uma das principais características das narrativas policiais é a sustentação do raciocínio lógico o qual implica, justamente, a ordenação do pensamento sequenciado (em variações conforme o autor), em que sentido um trabalho sistematizado de leitura e escrita dentro desse gênero narrativo implicaria a ampliação de repertório de alunos, ou seja, permitiria a eles se apropriarem de aspectos dessa leitura e, sobretudo, escrita? Partindo da prática de leitura em suspense1, a pesquisa desse projeto centrou-se, principalmente, em tentar conceber uma estratégia de escrita que permitisse não somente aos alunos experimentarem o processo de escrita com menos rejeição (como ocorre comumente) como também, ampliarem seu repertório no que diz respeito ao gênero estudado, sobretudo porque essa a questão do raciocínio lógico perpassa vários outros gêneros textuais. Trabalhamos com uma turma de 9o ano do Ensino Fundamental de uma escola pública no município de Volta Redonda, no Estado do Rio de Janeiro, que permita aos alunos ampliarem seu repertório no que concerne à leitura de narrativa policial. Elegemos como autor literário para a pesquisa a escritora Agatha Christie, particularmente com um conto em que o investigador é o clássico detetive Hercule Poirot. Apoiamo-nos, teoricamente, nas teorias do letramento (SOARES), particularmente do letramento literário (AGUIAR e COSSON), na teoria do efeito estético (ISER), de leitura compartilhada (COLOMER), mediação (PETIT) e nas concepções de narrativas policiais de Todorov. Temos como metodologia a pesquisa-ação, visto não somente o caráter interventivo da pesquisa como também a participação efetiva do professor pesquisador em sala de aula.
It’s ordinary to listen today, when debating issues of reading and text production in the classroom of Elementary School, that student should contact with a wide range of texts, for that you can expand knowledge of the language, using in it in order to achieve the desired goals. In this way, It’s essential that explore the most diverse text genres, regardless of that textual typology it predominates. However, at least in my practice, I see a tendency to favour, especially with the work of writing when we focus opinion text, argumentative dialogue, critical review, among others who have predominantly argumentative text-type. Another fact that always caught my attention, while elementary school teacher, is that the narratives, that involve the investigative perspective, such as the police narratives, like them enough. In general, they experience these narratives in film, and, in your vast majority, in TV series like Dexter and 24 Horas. In this way, we have formulated the following investigative hypothesis: considering that one of the main features of narratives cops is the logical-rational support, which implies the ordering of thought sequenced (in variations as the author), in that way a systematic work of reading and writing in this narrative genre, would change the expansion of repertoire of students, in other words, would allow them to take ownership of aspects of that reading and writing? Starting from the reading practice in suspense1 , the research of this project focused in trying to devise a strategy of writing that allowed not only to students try the writing process with less rejection as also, extend your repertoire with regard to genre studied especially because the point of logical reasoning pervades several other genres. We work with a class of ninth grade of Elementary School of public school in the municipality of Volta Redonda in the state of Rio de Janeiro, that allow students to extend your repertoire with regard to police narrative reading. We elect as literary author for research the writer Agatha Christie, particularly with the tales in which the investigator is the classic detective Hercule Poirot. We support, theoretically, in the theories of Literacy (SOARES), particularly the Literary Literacy (COSSON), in the theory of Aesthetic Effect (ISER), shared reading (COLOMER), mediation (PETIT), and on the conceptions of narratives of Todorov. We have how action research methodology seen not only the character of intervention research as well as the effective participation of the teacher in the classroom.

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Souza, Alexandre Pinho dos Santos. "Aplicações cosmológicas do campo espinorial ELKO /". Guaratinguetá, 2016. http://hdl.handle.net/11449/144451.

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Orientador: Álvaro de Souza Dutra
Coorientador: Álvaro de Souza Dutra
Banca: Elias Leite Mendonça
Banca: Denis Dalmazi
Banca: Roldão da Rocha Júnior
Banca: José Abdala Helayë-Neto
Resumo: Dentro da cosmologia, o modelo ΛCDM é considerado, pela comunidade científica, como aquele que melhor descreve o universo. Todavia, tal modelo sofre de alguns males que ainda precisam ser sanados. Entre eles se destacam o problema da constante cosmológica e o problema da coincidência cósmica. Atribui-se, neste modelo, a expansão acelerada do universo a um ente de origem desconhecida, chamado de energia escura. Parte da solução destes problemas está intimamente ligado em saber a natureza da energia escura. Por outro lado, devido a propriedades intrínsecas do espinor ELKO, faz-se possível atribuir ao mesmo o papel de energia escura. Deste modo, constrói-se aplicações cosmológicas do ELKO que possibilitem a resolução completa ou parcial dos problemas mencionados. Estas aplicações consistem basicamente na análise do sistemas de equações de Friedmann oriundas da anexação do Lagrangeano do ELKO na ação de Einstein-Hilbert. Dentro desse sistema se insere a mão o possível decaimento do ELKO em outros elementos que constituem o universo. Com este se alivia o problema da coincidência cósmica, enquanto que se confirma que o ELKO pode figurar como energia escura por meio dos resultados do sistema geral. Ao fim do trabalho se observa uma outra aplicação do ELKO, desta vez no cenário cosmológico de Einstein-Cartan. Neste se mostra que o modelo cosmológico que contém o ELKO como energia escura, e na presença de termo de torção, é análogo ao modelo cosmológico Λ(t)
Abstract: In cosmology the ΛCDM model is the most accepted way to describe the universe. However, this model suffers some problems that have to be solved. Namely there are two of them which are attached in this thesis. They are the cosmic coincidence and the cosmological constant problem. Due this model it is possible to relate the universe's accelerated expansion to dark energy. Part of solving these problems pass through knowing the origin of dark energy. It is known that the spinor ELKO has some fundamental properties that able scientists to connect them to dark universe elements, e.g. dark energy. So, some applications of ELKO in cosmology have been made in order to explore this possibility and to solve those fundamental problems. These application are based on analyzing ELKO in dynamical systems formed by Friedmann's equations, where these equations comes from putting ELKO's Lagranian in the Einstein-Hilbert action. In this system it is inserted a term of decaying. With such term it is possible to alleviate cosmic coincidence problem. On the other hand it is also possible to justify ELKO as dark energy as wished at the beginning. Last but not least, another application of ELKO in cosmology has been investigated. For such case is was shown that, with some considerations and approximations, ELKO in cosmology allied with Einstein-Cartan formalism can mimic Λ(t) cosmology results
Doutor

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Lizárraga, Olivares Kevin Angello. "Ondas gravitacionales en el espacio tiempo de De Sitter". Bachelor's thesis, Universidad Nacional Mayor de San Marcos, 2017. https://hdl.handle.net/20.500.12672/7586.

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Revisión detallada de los cálculos e ideas sobre las ondas gravitacionales en espacio-tiempo plano, del modelo de De Sitter para el universo y así llegar al desarrollo de las repercusiones que tiene la expansión del universo en la propagación de las ondas gravitacionales, la obtención de un radio crítico, fuera del cual no es posible la detección de las mismas.
Tesis

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48

Saïtta, Adrien. "Modélisation élastoplastique du comportement mécanique des sols. Application à la liquéfaction des sables et à la sollicitation d'expansion de cavité". Phd thesis, Ecole Nationale des Ponts et Chaussées, 1994. http://tel.archives-ouvertes.fr/tel-00523272.

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L'étude présentée dans ce mémoire se propose de réfléchir sur les relations existant entre une sollicitation homogène de laboratoire telle que l'essai triaxial classique, et une sollicitation non homogène telle que l'expansion de cavité cylindrique, le lien entre les deux types de sollicitation étant réalisé via un modèle de comportement. Ainsi, le premier chapitre constitue une étude bibliographique destinée à faire le point sur les éléments essentiels concernant la rhéologie des sables et sur les modèles de comportement actuellement utilisés. Le deuxième chapitre propose une nouvelle modélisation du comportement mécanique des sables qui s'inscrit entièrement dans le cadre élastoplastique et, dont l'objectif principal est de prendre en compte la notion de paramètre d'état (Been et Jefferies, 1985) et plus récemment d'indice d'état (Ishihara, 1993) sur le comportement de type lâche ou dense du sable. Le dernier chapitre, est consacré à l'étude des expansions de cavité à partir des modèles basés sur l'élastoplasticité généralisée (Zienkiewiez Pastor et Leung 1985). Ce modèle est tout d'abord appliqué à la sollicitation pressiométrique monotone et cyclique dans des sols cohérents avec prise en compte du couplage eau-squelette. Le cas des sables est finalement étudié, en mettant en oeuvre dans le code de calcul développé pour cette étude le modèle de Pastor, Leung et Zienkiewiez (1985) et en comparant les simulations obtenues à des essais réalisés au cylindre épais par Dupla (1995) dont la sollicitation est proche de la sollicitation pressiométrique. On montre comment à partir de l'essai pressiométrique cyclique, il est possible d'évaluer par démarche inverse le potentiel de liquéfaction d'un massif sableux.

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Costa, Rafael Vilaça Epifani. "O novo templo de Salomão: o projeto de expansão da Igreja Universal do Reino de Deus para o Brasil e o mundo". Universidade Católica de Pernambuco, 2017. http://www.unicap.br/tede//tde_busca/arquivo.php?codArquivo=1307.

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Abstract (sommario):

A construção do Templo de Salomão intitulado neste trabalho como Novo Templo de Salomão foi anunciada no ano de 2010, pelo Bispo Edir Macedo, como um grandioso projeto a ser realizado na cidade de São Paulo pela Igreja Universal do Reino de Deus. Desde a sua inauguração, no ano de 2014, notou-se que, além de uma judaização da estética aplicada a este espaço sagrado com a utilização de objetos, paramentos e decoração com motivos judaicos , a práxis iurdiana passou por mudanças substanciais, que incluem aspectos doutrinários, discursivos, litúrgicos, arquitetônicos e simbólicos, que afetaram todos os templos da denominação. Tais mudanças refletem diretamente o sentido que a IURD está tentando construir em torno dos elementos que constituem o seu novo santuário. As origens, os motivos e o modo como se dá esse processo de ressignificação da simbologia judaica, realizado pela Universal, é o cerne para se compreender o que está por trás desse empreendimento único no mundo, que foi escolhido como objeto de estudo deste trabalho. O intuito desta pesquisa é mostrar que, além de ser um megatemplo construído na capital paulista e o símbolo máximo de poder da denominação fundada por Edir Macedo, o Novo Templo de Salomão se constitui em um projeto de expansão da Igreja Universal do Reino de Deus para os próximos anos.
The construction of the Temple of Solomon - in this work named as New Temple of Solomon - was announced in 2010 by Bishop Edir Macedo as a great project to be held in São Paulo City by the Universal Church of the Kingdom of God (UCKG). Since its birth in 2014, in addition to a convertion of its aesthetics (or appearance) applied in this sacred space with the use of objects, vestments and decoration with Jewish motifs , the UCKG praxis underwent substantial changes; which include doctrinal, discursive, liturgical, architectural, and symbolic aspects that affected all temples from this denomination. Such changes directly reflect the sense that the UCKG is trying to build around the elements that constitute its new sanctuary. The origins, motives and the way in which this process of resignification of the Jewish symbolism, realized by the Universal, is the core to understand what is behind this unique enterprise in world, that was chosen like the main study object of this work. The purpose of this research is to show that, besides being a mega temple built in the capital of the homonymous state of São Paulo and the maximum symbol of power of the denomination founded by Edir Macedo, the New Temple of Solomon is an expansion project from Universal Church of the Kingdom of God for the next years.

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50

Fortes, Hemily Gomes Marciano. "Partículas massivas de spin-2 em espaços curvos de fundo". Universidade Estadual Paulista (UNESP), 2018. http://hdl.handle.net/11449/153629.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Partículas massivas de spin-2 são usualmente descritas pela conhecida teoria de Fierz-Pauli através de um tensor de rank-2 simétrico hµν = hνµ. Recentemente, tem havido um aumento no interesse por teorias que descrevam esse tipo de partícula, principalmente pela possibilidade de oferecer uma explicação alternativa para o problema da aceleração da expansão do universo, pois se o gráviton tivesse uma pequena massa, a força gravitacional diminuiria a grandes distâncias, produzindo tal aceleração. Trabalhos mais recentes têm trazido à tona outras possibilidades além de Fierz-Pauli para se descrever partículas de spin-2 massivas partindo de um tensor de rank-2 não simétrico eµν 6= eνµ, os chamados modelos L(a1). Tendo em vista que toda partícula deve interagir com a gravitação, no presente trabalho buscamos estudar o acoplamento desses novos modelos com um campo gravitacional de fundo. Para isso, a partir da manipulação das equações de movimento, procuramos obter os vínculos necessários para se ter uma teoria com a contagem de graus de liberdade correta. Fizemos também um estudo preliminar da versão sem massa dos modelos L(a1) no espaço curvo a partir da análise das simetrias de gauge existentes. Identificamos ainda os modelos parcialmente simétricos presentes em L(a1)
Massive spin-2 particles are usually described by the well-known Fierz-Pauli theory via a symmetric rank-2 tensor hµν = hνµ. Recently there has been an increase of interest in theories describing this kind of particle, especially because they can contribute to explain the accelerated expansion of the universe, since if the graviton has a small mass, the gravitational force would decrease at large distances, producing such accelerattion. In recent works other possibilities, besides the Fierz-Pauli model, which describe massive spin-2 particles starting from a non-symmetric rank-2 tensor eµν 6= eνµ have been found, the so-called L(a1) models. Since every particle has to interact with the gravitation, we have studied the coupling of the new models with a background gravitational field. Therefore, from the manipulation of the equations of motion, we seek for the necessary constraints in order to achieve the correct counting of degrees of freedom. We also have done a preliminary study of the massless version of the L(a1) models in the curved space from the analysis of the gauge symmetries of the theory. We also have identified the partially symmetric models present in L(a1).
2013/25368-0

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