Дисертації з теми "Cosmology: large-scale structure of Universe"
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Dupuy, Hélène. "Precision cosmology with the large-scale structure of the universe." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066245/document.
Повний текст джерелаThis thesis provides innovative results of different types. What they have in common is the quest for precision in the description of the physical phenomena at work in the universe. First, a toy model mimicking the propagation of light in an inhomogeneous spacetime has been presented. In this study, we chose a traditional Swiss-cheese representation. Often used in the litterature, such models offer the advantage of dealing with exact solutions of the Einstein equations, which do not affect the global dynamics of the universe while making it strongly inhomogeneous. We have exemplified how initial presumptions, such as the cosmological principle, can alter scientific conclusions, such as the estimation of cosmological parameters from Hubble diagrams. This work resulted in two publications in 2013, one in Physical Review D and another one in Physical Review Letter. The major result exposed in this thesis is the proposition of a new way of dealing with the neutrino component in cosmology. The idea is to decompose neutrinos into several single-flow fluids in order to get rid of velocity dispersion in each of them. The research field to which it belongs is the study of the formation of the large-scale structure of the universe thanks to cosmological perturbation theory in the relativistic and/or nonlinear regimes. This work resulted in three publications in JCAP, one in 2014 and two in 2015
Mehta, Kushal Tushar. "Measuring the Universe with High-Precision Large-Scale Structure." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/325226.
Повний текст джерелаMcGill, Colin Andrew. "The large-scale structure of the universe : some theoretical considerations." Thesis, University of Oxford, 1987. http://ora.ox.ac.uk/objects/uuid:967fd0f2-817e-48ae-b57c-c1fb0dd435fb.
Повний текст джерелаNtelis, 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.
Повний текст джерелаThis 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
Hatton, Stephen John. "Probing the large-scale structure of the Universe with future galaxy redshift surveys." Thesis, Durham University, 1999. http://etheses.dur.ac.uk/4494/.
Повний текст джерелаMelia, Fulvio. "The linear growth of structure in the Rh = ct universe." OXFORD UNIV PRESS, 2017. http://hdl.handle.net/10150/622916.
Повний текст джерелаManti, Serena. "Cosmic large scale structure: insights from radio astronomical experiments." Doctoral thesis, Scuola Normale Superiore, 2016. http://hdl.handle.net/11384/85877.
Повний текст джерелаCroft, Rupert Alfred Charles. "Galaxy clusters and the formation of large-scale structures in the universe." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308751.
Повний текст джерелаHoyle, Fiona. "The structure and scale of the universe." Thesis, Durham University, 2000. http://etheses.dur.ac.uk/4250/.
Повний текст джерелаCollis, Olivari Lucas. "Intensity mapping : a new approach to probe the large-scale structure of the Universe." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/intensity-mapping-a-new-approach-to-probe-the-largescale-structure-of-the-universe(cd5b7586-7210-441e-838f-545d397893e5).html.
Повний текст джерелаVan, De Rijt Nicolas. "Signatures of the primordial universe in large-scale structure surveys." Palaiseau, Ecole polytechnique, 2012. http://pastel.archives-ouvertes.fr/docs/00/72/78/11/PDF/PhDthesis.pdf.
Повний текст джерелаThe study of the large-scale structure of the Universe is one of the most important tools used to understand the origin and evolution of the Universe. In this thesis, we focus on two different facets of this study: cosmological perturbation theory and cosmic shear. Cosmological perturbation theory describes how the large-scale structure of the Universe has been created out of the tiny initial perturbations. This evolution is described using fluid equations, and in this thesis, we introduce new versions of this Boltzmann hierarchy. The advantages and disadvantages of each hierarchy are thoroughly analysed. We also introduce a novel technique, dubbed the eikonal approximation, which enables us to better understand the results of existing perturbation theory approaches. Moreover, its broad range of applicability allows us to generalise many results. Cosmic shear describes how gravitational lensing deforms the image of the sky. In this thesis, we compute in great detail the bispectrum of cosmic shear to second order in the gravitational potentials. The complete calculation is done on the full sky, making the results much more general than the existing ones. To ease the otherwise impossible numerical calculations, we introduce the (extended) Limber approximation
Leaf, Kyle, and Fulvio Melia. "A two-point diagnostic for the H ii galaxy Hubble diagram." OXFORD UNIV PRESS, 2018. http://hdl.handle.net/10150/627132.
Повний текст джерелаKwan, J., C. Sánchez, J. Clampitt, J. Blazek, M. Crocce, B. Jain, J. Zuntz, et al. "Cosmology from large-scale galaxy clustering and galaxy–galaxy lensing with Dark Energy Survey Science Verification data." OXFORD UNIV PRESS, 2017. http://hdl.handle.net/10150/623270.
Повний текст джерелаMarcondes, Rafael José França. "Interacting dark energy models in Cosmology and large-scale structure observational tests." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-17102016-123725/.
Повний текст джерелаA cosmologia moderna oferece um ótimo entendimento do universo com uma precisão impressionante, possibilitada pelas tecnologias modernas das gerações mais novas de telescópios. O modelo cosmológico padrão, porém, não é livre de problemas do ponto de vista teórico, deixando perguntas ainda sem respostas. Uma possibilidade que tem sido proposta é a existência de um acoplamento entre setores escuros. A ideia de uma interação entre os componentes escuros poderia ajudar os físicos a entender por que vivemos em uma época do universo na qual a matéria escura e a energia escura são comparáveis em termos de densidades de energia, o que pode ser considerado uma estranha coincidência dado que suas evoluções com o tempo são completamente diferentes. Matéria escura e energia escura são geralmente tratadas como fluidos perfeitos. A interação é introduzida ao permitirmos um tensor não nulo no lado direito das equações de conservação dos tensores de energia-momento. Prosseguimos com uma abordagem fenomenológica para testar modelos de interação com observações de distorções no espaço de redshift. Em um universo plano composto apenas por esses dois fluidos, consideramos, separadamente, duas formas de interação, através de termos proporcionais às densidades de energia escura e de matéria escura. Uma expressão analítica para a taxa de crescimento aproximada por f = Omega^gamma, onde Omega é a contribuição percentual da matéria escura para o conteúdo do universo e gamma é o índice de crescimento, é deduzida em termos da interação e de outros parâmetros do modelo no primeiro caso, enquanto para o segundo caso mostramos que uma interação não nula não pode ser acomodada pela aproximação do índice de crescimento. As expressões obtidas são então utilizadas para comparar as previsões com dados observacionais de crescimento de estruturas em um programa para Monte Carlo via cadeias de Markov. Concluímos que tais dados atuais por si só não são capazes de restringir a interação devido às suas grandes incertezas. Utilizamos também observações de aglomerados de galáxias para analisar seus estados viriais através da equação de Layzer-Irvine modificada a fim de detectar sinais de interação. Obtemos medições de taxas viriais observadas, constante de interação, taxa virial de equilíbrio e desvio do equilíbrio para um conjunto de aglomerados. Uma análise combinada indica uma constante de interação 0.29^{+2.25}_{-0.40}, compatível com zero, mas uma taxa virial de equilíbrio combinada de 0.82^{+0.13}_{-0.14}, o que significa uma detecção em um intervalo de confiança de 2 sigma. Apesar desta tensão, o método produz resultados encorajadores enquanto ainda permite melhorias, possivelmente pela remoção da suposição de pequenos desvios do equilíbrio.
Baxter, Eric J., Eduardo Rozo, Bhuvnesh Jain, Eli Rykoff, and Risa H. Wechsler. "Constraining the mass–richness relationship of redMaPPer clusters with angular clustering." OXFORD UNIV PRESS, 2016. http://hdl.handle.net/10150/622071.
Повний текст джерелаIlić, Stéphane. "The large scale structures. A window on the dark components of the Universe." Thesis, Paris 11, 2013. http://www.theses.fr/2013PA112243/document.
Повний текст джерелаThe dark energy is one of the great mysteries of modern cosmology, responsible for the current acceleration of the expansion of our Universe. Its study is a major focus of my thesis : the way I choose to do so is based on the large-scale structure of the Universe, through a probe called the integrated Sachs-Wolfe effect (iSW). This effect is theoretically detectable in the cosmic microwave background (CMB) : before reaching us this light travelled through large structures underlain by gravitational potentials. The acceleration of the expansion stretches and flattens these potentials during the crossing of photons, changing their energy, in a way that depend on the properties of the dark energy. The iSW effect only has a weak effect on the CMB requiring the use of external data to be detectable. A conventional approach is to correlate the CMB with a tracer of the distribution of matter, and therefore the underlying potentials. This has been attempted numerous times with galaxies surveys but the measured correlation has yet to give a definitive result on the detection of the iSW effect. This is mainly due to the shortcomings of current surveys that are not deep enough and/or have a too low sky coverage. A part of my thesis is devoted to the correlation of FDC with another diffuse background, namely the cosmological infrared background (CIB), which is composed of the integrated emission of the non-resolved distant galaxies. I was able to show that it is an excellent tracer, free from the shortcomings of current surveys. The levels of significance for the expected correlation CIB-CMB exceed those of current surveys, and compete with those predicted for the future generation of very large surveys. In the following, my thesis was focused on the individual imprint in the CMB of the largest structures by iSW effect. My work on the subject first involved revisiting a past study of stacking CMB patches at structures location, using my own protocol, completed and associated with a variety of statistical tests to check the significance of these results. This point proved to be particularly difficult to assess and subject to possible selection bias. I extended the use of this detection method to other available catalogues of structures, more consequent and supposedly more sophisticated in their detection algorithms. The results from one of them suggests the presence of a signal at scales and amplitude consistent with the theory, but with moderate significance. The stacking results raise questions regarding the expected signal : this led me to work on a theoretical prediction of the iSW effect produced by structures, through simulations based on the Lemaître-Tolman-Bondi metric. This allowed me to predict the exact theoretical iSW effect of existing structures. The central amplitude of the measured signals is consistent with the theory, but shows features non-reproducible by my predictions. An extension to the additional catalogues will verify the significance of their signals and their compatibility with the theory. Another part of my thesis focuses on a distant time in the history of the Universe, called reionisation : the transition from a neutral universe to a fully ionised one under the action of the first stars and other ionising sources. This period has a significant influence on the CMB and its statistical properties, in particular the power spectrum of its polarisation fluctuations. In my case, I focused on the use of temperature measurements of the intergalactic medium during the reionisation in order to investigate the possible contribution of the disintegration and annihilation of the hypothetical dark matter. Starting from a theoretical work based on several models of dark matter, I computed and compared predictions to actual measures of the IGM temperature, which allowed me to extract new and interesting constraints on the critical parameters of the dark matter and crucial features of the reionisation itself
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.
Повний текст джерелаIn 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
Sánchez, C., J. Clampitt, A. Kovacs, B. Jain, J. García-Bellido, S. Nadathur, D. Gruen, et al. "Cosmic voids and void lensing in the Dark Energy Survey Science Verification data." OXFORD UNIV PRESS, 2017. http://hdl.handle.net/10150/623046.
Повний текст джерелаIlic, Stéphane. "The large scale structures. a window on the Dark components of the Universe." Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00933818.
Повний текст джерелаGnedin, Nickolay Y., George D. Becker, and Xiaohui Fan. "Cosmic Reionization on Computers: Properties of the Post-reionization IGM." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/624497.
Повний текст джерелаLeaf, Kyle, and Fulvio Melia. "Analysing H(z) data using two-point diagnostics." OXFORD UNIV PRESS, 2017. http://hdl.handle.net/10150/625514.
Повний текст джерелаLeistedt, B., H. V. Peiris, F. Elsner, A. Benoit-Lévy, A. Amara, A. H. Bauer, M. R. Becker, et al. "MAPPING AND SIMULATING SYSTEMATICS DUE TO SPATIALLY VARYING OBSERVING CONDITIONS IN DES SCIENCE VERIFICATION DATA." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/622062.
Повний текст джерелаFreudenburg, Jenna Kay Cunliffe. "Precision Cosmology with Weak Gravitational Lensing and Galaxy Populations." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595544137004009.
Повний текст джерелаMore, Surhud, Hironao Miyatake, Masahiro Takada, Benedikt Diemer, Andrey V. Kravtsov, Neal K. Dalal, Anupreeta More, et al. "DETECTION OF THE SPLASHBACK RADIUS AND HALO ASSEMBLY BIAS OF MASSIVE GALAXY CLUSTERS." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621397.
Повний текст джерелаZeng, Houdun, Fulvio Melia, and Li Zhang. "Cosmological tests with the FSRQ gamma-ray luminosity function." OXFORD UNIV PRESS, 2016. http://hdl.handle.net/10150/621735.
Повний текст джерелаFromont, Paul de. "Cosmologie et gravité des régions sphériques compensées." Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC148/document.
Повний текст джерелаThis thesis is devoted to the study of the imprints of dark energy on the formation of the large scale structures in the Universe. I define the spherically compensated cosmic regions as the large-scale environment around local extrema in the density field. For central minimum, this region can be identified with standard cosmic voids. Using numerical simulations, I show that these regions, once properly identified, can be used efficiently to distinguish competitive cosmological models. I show that the average shape of these density profiles and their statistical properties can be analytically computed in the primordial Universe. Using an appropriate dynamical formalism, I show that it is possible to follow the nonlinear evolution of these structures until today. This allows to reconstruct the shape of such large scale regions from first principles. I exhibit a fundamental property of these regions which maintains constant a particular size : the compensation radius. Around this radius, the nonlinear evolution of the matter field can be analytically derived. By studying the gravitational collapse in gravity models beyond General Relativity, I show that it is possible to constrain efficiently both cosmology and the nature of gravity. Beside giving a physically motivated model for both shape and statistical properties of such large scale matter profile, this work also define new cosmological probes that could be used to test the nature of our Universe
Rubira, Henrique. "Melhorias na predição da estrutura de larga escala do universo por meio de teorias efetivas de campo." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-08102018-145202/.
Повний текст джерелаWith future cosmological surveys, cosmology will enter in the precision era. New data will improve the constraints on the standard cosmological model enhancing our knowledge about the universe history, its components and the behavior of gravity. In this context, it is vital to come up with precise theoretical predictions for the formation of large-scale structure beyond the linear regime. The best way of solving the fluid equations that describe the large-scale universe is through lattice simulations, which faces difficulties in the inclusion of accurate baryonic physics and is very computationally costly. Another approach is the theoreti- cal calculation of the correlation statistics through the perturbative approach, called Standard Perturbation Theory (SPT). However, SPT has several problems: for some cosmologies, it may not converge and even when it converges, we cannot be sure it converges to the right result. Also, it contains a special scale that is the loop momenta upper-bound in the integral. In this work, we show results for the 3-loop calculation. The term of third order is larger than the terms of 2-loops and 3-loops, making explicit SPT problems. In this work, we describe the recent usage of Effective Field Theories (EFTs) on Large Scale Structure problems to correct SPT issues and complement cosmological simulations. EFTs are used in other areas of physics, such as low energy QCD, serving as a complement to lattice calculations. EFT improves the predictions for the matter power spectrum and bispectrum by adding counterterms that need to be fitted. The free parameters, instead of being a problem, bring relevant information about how the small-scale physics affects the scales for which we are trying to make statistical predictions. We show the calculation of the 3-loop EFT counterterms. EFTs are also used to explain main points connecting the matter density field with tracers like galaxies and halos. EFTs highlighted how to construct a complete basis of operators that parametrize the bias. We explain how we can use EFT to improve the bias prediction to non-linear scales. We compute the non-linear halo-bias by fitting the bias parameters in simulations. We also show the EFT renormalization in Lagrangian coordinates. Finally, we explain another critical EFT application to cosmology: in primordial physics. It can be used to parametrize deviations to the slow-roll theory within the inflationary paradigm.
Laigle, Clotilde. "Observational and theoretical constraints on galaxy evolution at high redshift." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066343.
Повний текст джерелаI present in this thesis new constraints on galaxy formation and evolution while studying the galaxy mass growth and the co-evolution of the cosmic web and the embedded galaxies, from the epoch of cosmic dawn to today.To do so, I first created a new photometric catalog on the COSMOS field with precise photometric redshifts allowing to probe accurately the high-redshift Universe. I analyze this survey while relying heavily on comparisons with virtual galaxy surveys produced from state-of-the- art cosmological hydrodynamical simulations, which capture all our current knowledge of galaxy formation and evolution.From this comparative analysis, in the first part of my thesis I show that the redshift evolution of galaxy properties is reasonably well understood when invoking mass-dependent processes (AGN and stellar feed- back). I highlight also the effect of simplifying assumptions inherent to our observational methods, which bias the physical properties computed from galaxy photometry.Galaxies and haloes are embedded in the cosmic web, an intricate large-scale structure of walls, filaments and nodes. In the second part of my thesis, I show how galaxies and dark haloes gain their angular momentum from the large-scale flow, implying that some of their properties depend on their anisotropic filamentary environment. I then extract the filamentary structure from the observed photometric catalog and measure the dependence of galaxy properties to the anisotropic environment. I find mass and colour gradients towards the filaments. In turn it emerges that galaxy masses and angular momenta are two dependent quantities impacted by their anisotropic environment
Petrie, Stephen. "Determining the characteristic mass of DLA host haloes from 21cm fluctuations." Connect to thesis, 2010. http://repository.unimelb.edu.au/10187/7159.
Повний текст джерелаWe then fit the analytic 21cm power spectrum generated using this formalism to a simulated 21cm power spectrum, with the characteristic mass of DLA host haloes being used as a fitting parameter. The DLA host halo mass is in turn dependent upon two parameters in our model: the minimum mass of haloes M_{min} included in our formalism, and the HI weighting index alpha_{HI}. The neutral hydrogen fraction is another parameter, which we can choose to be the same as that from our simulation volume. If we also choose a value for alpha_{HI} that is motivated by analysis of the dark matter and HI gas content of the haloes in the simulation, then we are able to fit the 21cm power spectrum at both large and small scales, with an M_{min} that is the same or similar to the lowest mass in the simulation's halo catalogue. This in turn gives a similar value for the DLA host halo mass that is known to be the case in the simulation. This demonstrates the viability of the Wyithe (2008) method for determining the DLA host halo mass using observations of 21cm fluctuations. However, degeneracies in the free parameters of our analytic formalism would hinder an accurate determination of the DLA host halo mass from actual future observations. This is due to the fact that the real space, spherically averaged 21cm power spectrum is used throughout this thesis. However, extending our analytic formalism to the redshift space, angular-dependent 21cm power spectrum should be capable of breaking the degeneracy between DLA host halo mass and neutral hydrogen fraction.
Wibking, Benjamin Douglas. "Cosmic structure formation on small scales: From non-linear galaxy clustering to the interstellar medium." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1561556033289855.
Повний текст джерелаPond, Jarrad W. T. "Perturbation analysis of fluctuations in the universe on large scales, including decaying solutions and rotational velocities." Honors in the Major Thesis, University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/1309.
Повний текст джерелаBachelors
Sciences
Physics
Codis-Decara, Sandrine. "De la cosmologie à la formation des galaxies : que nous apprennent les grandes structures de l'Univers ?" Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066343/document.
Повний текст джерелаThis thesis by publication is devoted to the theoretical understanding of the large-scale structure of the Universe and its role in the context of cosmology and galaxy formation. The birth and evolution of galaxies occur within the large cosmic highways drawn by the cosmic web and the natural question which arises is whether galaxies retain a memory of the large-scale cosmic flows from which they emerge. To address this key question, we will first show that in cosmological simulations, the spin of galaxies and the direction of their host filament are correlated in a mass-dependent way. This signal will be shown to be qualitatively understood in the context of hierarchical structure formation. An analytic model which explicitly takes into account the anisotropy of the cosmic web will complement this qualitative understanding by reproducing the measured correlations. Those ideas are important to understand the evolution of galaxy morphology but also to understand the intrinsic alignments of galaxies that contaminate cosmological probes like cosmic shear experiments. We will in particular measure this contamination directly from a state-of-the-art hydrodynamical simulation. In a second part, we will address the question of how to efficiently use large-scale structure data to probe the cosmological model describing our Universe by measuring its topology and geometry and using perturbation theory in the weakly and even mildly non-linear regime. The major contribution of this work is to analytically study the effect of redshift space distortions and non-linear collapse of structures on the topology, geometry and statistics of the cosmic density field
Dupuy, Alexandra. "Du HI radio à la mesure de la croissance des bassins gravitationnels." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1201/document.
Повний текст джерелаMotions of galaxies in the universe are due to the rivalry between the expansion of the universe and gravitation. This tug-of-war impacts the formation and the growth of large scale structures of the universe. Thus, depending on the identity of the winner of this duel, the universe is more or less compact. Within this context, this PhD thesis is divided into three parts, spanning from HI observations to the estimate of the growth of rate of large scale structures of the universe and the compactness of the local universe.The Cosmicflows collaboration assembles catalogues of galaxy distances. Up to now, three catalogues have been published, the last one being Cosmicflows-3. This thesis presents and analyses observational data obtained from HI observations. These new data will be used to construct the new compilation of distances Cosmicflows-4 by the use of the Tully-Fisher relation, in order to correct the lack of data in the Northern celestial hemisphere in the current catalog.From the distance of a galaxy, one can derive the radial part of its peculiar velocity corresponding to the component of its total velocity caused by gravitation. Peculiar velocities allow to probe the matter content of the universe and to extract information on large scale structures of the universe. Two methodologies using peculiar velocities have been developed during this thesis to characterize large scale structures of the local universe.On the one hand, peculiar velocity catalogues can be used to reconstruct tri-dimensional velocity fields. These velocity field allow one to map the structure of the local universe and are used in this thesis to identify gravitational basins and valleys within the local universe by computing streamlines.On the other hand, a method based on the analysis of two-point galaxy peculiar velocity correlations has been developed in order to constrain the growth rate of large scale structures of the local universe from observational data. This method is applied to the Cosmicflows-3 catalogue of observed peculiar velocities
Kodi, Ramanah Doogesh. "Bayesian statistical inference and deep learning for primordial cosmology and cosmic acceleration." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS169.
Повний текст джерелаThe essence of this doctoral research constitutes the development and application of novel Bayesian statistical inference and deep learning techniques to meet statistical challenges of massive and complex data sets from next-generation cosmic microwave background (CMB) missions or galaxy surveys and optimize their scientific returns to ultimately improve our understanding of the Universe. The first theme deals with the extraction of the E and B modes of the CMB polarization signal from the data. We have developed a high-performance hierarchical method, known as the dual messenger algorithm, for spin field reconstruction on the sphere and demonstrated its capabilities in reconstructing pure E and B maps, while accounting for complex and realistic noise models. The second theme lies in the development of various aspects of Bayesian forward modelling machinery for optimal exploitation of state-of-the-art galaxy redshift surveys. We have developed a large-scale Bayesian inference framework to constrain cosmological parameters via a novel implementation of the Alcock-Paczyński test and showcased our cosmological constraints on the matter density and dark energy equation of state. With the control of systematic effects being a crucial limiting factor for modern galaxy redshift surveys, we also presented an augmented likelihood which is robust to unknown foreground and target contaminations. Finally, with a view to building fast complex dynamics emulators in our above Bayesian hierarchical model, we have designed a novel halo painting network that learns to map approximate 3D dark matter fields to realistic halo distributions
Mourier, Pierre. "Cosmologie inhomogène relativiste : modèles non perturbatifs et moyennes spatiales des équations d’Einstein." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1116/document.
Повний текст джерелаIn the standard model of cosmology, the global dynamics of the Universe is modelled via a highly symmetric background spacetime with homogeneous and isotropic spatial sections. The coupling of the homogeneous fluid sources to the overall expansion is then determined by the Einstein equations of General Relativity. In addition, the formation of inhomogeneous matter structures is described either via a relativistic perturbation scheme assuming small deviations of all fields to the prescribed homogeneous background, or using Newtonian dynamics within the same expanding background, depending on the scale and epoch. However, the interpretation of observations within this model calls for an unexpectedly accelerated expansion requiring a poorly-understood `Dark Energy' component, in addition to Dark Matter. Inhomogeneous cosmology aims at relaxing the restrictions of these models on the geometry and sources while staying within the framework of General Relativity. It can allow, in particular, for an improved modelling of the formation of structures accounting for strong deviations from homogeneity in the matter distribution and the geometry. It can also study the dynamical consequences, or backreaction effects, of the development of such inhomogeneities on the expansion of larger scales. Such a backreaction may then reproduce, at least partially, the behaviours attributed to Dark Energy or Dark Matter. During my PhD under the direction of Thomas Buchert, I have been working on several analytical aspects of general-relativistic inhomogeneous cosmology. I present below the results of collaborations in which I played a major role in the context of the PhD. I first focussed on the expression of a relativistic Lagrangian approximation scheme for the description of the local dynamics of structures up to a nonlinear regime in irrotational perfect barotropic fluids. I then considered the effective description of inhomogeneous fluids with vorticity and a general energy-momentum tensor in terms of two possible schemes of spatial averaging. These schemes are applicable to any choice of spatial hypersurfaces of averaging, providing for each choice a set of effective evolution equations, featuring several backreaction terms, for an averaging region comoving with the sources. This allows for a qualitative discussion of the dependence of the average equations and backreactions on the foliation choice. I also studied the rewriting of such averaging schemes and evolution equations under a unified and manifestly 4-covariant form. This latter result will allow for a more explicit investigation of foliation dependence
Bel, Julien. "Les moments cumulant d'ordre supérieur à deux points des champs cosmologiques : propriétés théoriques et applications." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4715/document.
Повний текст джерелаThe philosophy of this thesis is that our best chances of finding and characterizing the essential ingredients of a well grounded cosmological model is by enlarging the arsenal of methods with which we can hunt for new physics. While it is of paramount importance to continue to refine, de-bias and power, the very same testing strategies that contributed to establish the concordance model, it is also crucial to challenge, with new methods, all the sectors of the current cosmological paradigm. This thesis, therefore, engages in the challenge of developing new and performant cosmic probes that aim at optimizing the scientific output of future large redshift surveys. The goal is twofold. From the theoretical side, I aim at developing new testing strategies that are minimally (if not at all) affected by astrophysical uncertainties or by not fully motivated phenomenological models. This will make cosmological interpretations easier and safer. From the observational side, the goal is to gauge the performances of the proposed strategies using current, state of the art, redshift data, and to demonstrate their potential for the future large cosmological missions such as BigBOSS and EUCLID
Rosdahl, Karl Joakim. "Cosmological RHD simulations of early galaxy formation." Thesis, Lyon 1, 2012. http://www.theses.fr/2012LYO10075/document.
Повний текст джерелаWith the increasing sophistication and efficiency of cosmological hydrodynamics codes, ithas become viable to include ionizing radiative transfer (RT) in cosmological simulations,either in post-processing or in full-blown radiation-hydrodynamics (RHD) simulations. Inspite of the many hurdles involved, there has been much activity during the last decade or soon different strategies and implementations, because a number of interesting problems canbe addressed with RT and RHD, e.g. how and when the Universe became reionized, howradiation from stars and active galactic nuclei plays a part in regulating structure formationon small and large scales, and what predictions and interpretations we can make of observedphenomena such as the Lyman-alpha forest and diffuse sources of radiation.This coincides with the advent of the James Webb space telescope (JWST) and otherstate-of-the-art instruments which are about to give us an unprecedented glimpse into theend of the dark ages of the Universe, when the cosmos switched from a cold and neutralstate to a hot and ionized one, due to the turn-on of ionizing radiative sources.With a primary interest in the problem of radiative feedback in early structure formation,we have implemented an RHD version of the Ramses cosmological code we call RamsesRT,which is moment based and employs the local M1 Eddington tensor closure. This code allowsus to study the effects of ionizing radiation on-the-fly in cosmological RHD simulationsthat take full advantage of the adaptive mesh refinement and parallelization strategies ofRamses. For self-consistent RHD we have also implemented a non-equilibrium chemistry ofthe atomic hydrogen and helium species that interact with the transported radiation.I present in this thesis an extensive description of the RamsesRT implementation andnumerous tests to validate it.Thus far we have used the RHD implementation to study extended line emission fromaccretion streams, which are routinely predicted to exist at early redshift by cosmologicalsimulations but have never been unambiguously verified by observations, and to investigatewhether gravitational heating in those streams could be the dominant power source ofso-called Lyman-alpha blobs, an observed phenomenon which has been much studied anddebated during the last decade or two. Our conclusions from this investigation are thatLyman-alpha blobs can in principle be powered by gravitational heating, and furthermorethat accretion streams are on the verge of being directly detectable for the first time withupcoming instruments.My future intent is to use RamsesRT for high-resolution cosmological zoom simulations ofearly galaxy formation, up to the epoch of reionization, to study how radiative feedbackaffects the formation and evolution of those galaxies and to make observational predictionsthat can be tested with upcoming instruments such as the JWST
Wallisch, Benjamin. "Cosmological probes of light relics." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/283003.
Повний текст джерелаSantiago, Bautista Iris del Carmen. "Étude des propriétés des galaxies dans les structures filamentaires." Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30034.
Повний текст джерелаThe baryonic component of the Large Scale Structure (LSS) of the Universe is composed by concentrations of gas and galaxies forming groups, clusters, elongated filaments and widely spread sheets which probably underline the distribution of dark matter. Nevertheless, according to the current cosmological models, most of the baryonic material in the Universe has not yet been directly observed. Numerical simulations suggest that from one-half to two-thirds of all baryons may be located out of clusters of galaxies, pervading the structures between them. The most concentrated structures, which we call systems of galaxies (i.e., groups and clusters) usually contain high density hot gas (1 - 10 keV) that cools radiatively, emits at X-rays wavelengths and interacts with the cosmic microwave background at millimeter wavelengths (Sunyaev Zel'dovich effect, SZ). For the less dense structures, filaments and sheets, the baryons are probably in moderately hot gas phase (0.01 - 1 keV), commonly named as warm hot intergalactic medium (WHIM). In this PhD Thesis, we study the environmental effects associated to the different components of the LSS. For the galaxy systems, we aim to characterize the intra cluster medium (ICM) through the analysis of the S-Z effect. We employ the ACT and Planck data to analyze the gas pressure profiles of a sample of low mass galaxy clusters. For the least dense structures, we assembled a sample of filament candidates composed by chains of clusters that are located inside superclusters of galaxies. We aim to probe the filament structure skeletons and characterize their components (galaxies, groups/clusters and gas)
Whitbourn, Joseph. "Exploring cosmology via large scale structure." Thesis, Durham University, 2013. http://etheses.dur.ac.uk/9459/.
Повний текст джерелаMa, Yin-Zhe. "Cosmology with CMB and large scale structure." Thesis, University of Cambridge, 2011. https://www.repository.cam.ac.uk/handle/1810/239394.
Повний текст джерелаSutherland, William James. "Large-scale structure in the universe." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317881.
Повний текст джерелаFantaye, Yabebal. "Probing primordial non-Gaussianity using large scale structure." Master's thesis, University of Cape Town, 2009. http://hdl.handle.net/11427/6101.
Повний текст джерелаIncludes bbliographical references (leaves 65-69).
Recent evidence from the WMAP satellite has lead to a tentative detection of non-Gaussianity. Using the bispectrum statistic applied to the MegaZ catalogue of over 600,000 luminous red galaxies we find new bounds on the large-scale nonGaussianity. We constrain the fNL parameter using a particular type of triangular configuration as well as the combination of all the possible triangles in harmonic space. The constraint on fNL from the combination of all possible triangular configurations is ffV'ial = 57 ± 52 with 68% confidence limit, which is consistent with vanishing primordial non-Gaussianity, although some triangular configurations on their own suggest a non-zero bispectrum which, if confirmed, would have a profound effect on modern cosmology.
Pediani, Steven. "Dark energy and large scale structure." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/dark-energy-and-large-scale-structure(44224ea0-265c-4d78-931a-298d79d3ab9d).html.
Повний текст джерелаKopp, Michael. "Models of large scale structure formation in cosmology." Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-172479.
Повний текст джерелаWenn wir all das Wissen kombinieren, welches wir bisher über Ursprung, Entwicklung und heutigen Zustand des Universum gesammelt haben, kommen wir unweigerlich zu dem Schluss, dass 95% der Materiedichte des Universums aus unbekannten Substanzen besteht, die man dunkle Materie und dunkle Energie nennt. Diese Dissertation beschäftigt sich mit verschiedenen Aspekten der Entstehung der größten Strukturen im Universum und entwickelt neue Methoden diese Strukturen, bestehend aus dem kosmischen Netz, Galaxienhaufen und Galaxien zu modellieren. Diese Strukturen hängen sehr sensibel von den Eigenschaften der dunklen Materie und dunklen Energie ab, insbesondere von ihren relativen und absoluten Mengen, sowie der Zustandsgleichung der dunklen Energie und einer eventuell von ihr vermittelten neuen Wechselwirkung. Aktuell durchgeführte und zukünftige Vermessungen der größten Strukturen kartographieren diese mit zunehmender Präzision und in immer größeren Volumen. Um die kosmologischen Parameter bestmöglich aus den Daten zu extrahieren, benötigen wir akkurate Modelle der Strukturbildung und der Prozesse, die das Licht auf seinem Weg zum Beobachter beeinflussen. Nur so können wir zuverlässig die kosmologischen Parameter rekonstruieren und die Modelle für dunkle Materie und dunkle Energie identifizieren die von den Daten bevorzugt werden. Somit trägt die Dissertation zu den Bemühungen bei, die Natur der dunklen Materie und dunklen Energie zu enthüllen. Kapitel 2 untersucht ein Modell für dunkle Energie, welche eine ``fünfte Kraft'' vermittelt, die jedoch die Newtonsche Gravitationskraft auf Grund des Chamäleon-Mechanismus lediglich auf großen Skalen verstärkt und eine Expansionsgeschichte verursacht, die nicht vom einfachsten Fall zu unterscheiden ist, bei dem die dunkle Energie eine kosmologische Konstante ist. Deswegen stehen die einzigen Beobachtungsgrößen, welche die Modelle zu unterscheiden vermögen im Zusammenhang mit Strukturbildung. Wir untersuchen mit semi-analytischen Methoden die Häufigkeit von dunkle-Materie-Halos pro Halo-Masse und erhalten für diese eine Fitfunktion, die vom Wert des neuen Modellparameters abhängt, welcher die Reichweite und Stärke der fünften Kraft bestimmt. Wir finden eine gute übereinstimmung der auf diese Weise bestimmten theoretischen Massenfunktion mit denjenigen bestimmt aus Monte-Carlo und N-Teilchen Simulationen. Die von uns gefundene Fitfunktion vermag das Modell durch Beobachtungen von Galaxienhaufen zu testen und kann dazu dienen nach den charakteristischen Signaturen des Chamäleon-Mechanismus in den Beobachtungsdaten zu suchen. In Kapitel 3 und 4 zeigen wir, dass die Newtonsche Gravitationstheorie anstelle der Allgemeinen Relativitätstheorie auf allen Längenskalen verwendet werden kann, um akkurat die Entstehung der größten Strukturen zu beschreiben, sofern das Universum von kalter dunkler Materie und einer kosmologischen Konstante dominiert wird. In Kapitel 5 zeigen wir, dass ein komplexes Skalarfeld, welches die Schrödinger-Poisson-Gleichung erfüllt, in der Lage ist kollisionsfreie selbstgravitierende dunkle Materie mit der selben Zahl an Freiheitsgraden zu beschreiben wie das weitverbreitete Staubmodell. Im Gegensatz zum Staubmodell ist das Skalarfeldmodell frei von Singularitäten, weswegen es analytische und numerische Studien von komplett nichtlinearen Prozessen wie Halo-Entstehung erlaubt. In Kapitel 6 untersuchen wir die Clusterung von Halos, oder die Halo-Korrelationsfunktion, wie sie im Rotverschiebungsraum beobachtet wird. Dazu entwickeln wir ein verbessertes Modell für die Dynamik von Halos, welches auf einer Körnung des Staubmodells und einer Verallgemeinerung des Gaussian-Streaming-Modells auf beliebige Phasenraumfunktionen beruht. Wir vergleichen unsere Resultate mit Messgrößen aus einer N-Teilchen-Simulation und finden, dass das granulierte Modell die Genauigkeit der vorhergesagten Korrelationsfunkionen im Rotverschiebungsraum wesentlich verbessert.
Sagredo, Briones Bryan Lester. "Bayesian statistical methods on large scale structure cosmology." Tesis, Universidad de Chile, 2018. http://repositorio.uchile.cl/handle/2250/168494.
Повний текст джерелаEn esta tesis se introduce el formalismo de la estadística Bayesiana aplicado a cosmología LCDM y otros modelos de energía oscura, enfocado en los observables de agrupamiento de galaxias y de crecimiento cósmico. Se explora un gran rango de aplicaciones del marco de trabajo Bayesiano. Primero, se exploran las posibilidades de predicción de la estadística Bayesiana con nuestro primer proyecto, el cual consiste en la aplicación del método de Aproximación de Verosimilitudes con Derivadas (DALI por sus siglas en inglés) para mejorar las predicciones de Matriz de Fisher de un experimento de agrupamiento de galaxias tipo LSST. El método contiene una expansión de Taylor hasta el tercer orden a partir del punto de parámetros de confianza, capturando formas de las regiones de confianza que van más allá de las usuales elipses de Fisher en la bibliografía. Además se compara con muestras de Cadenas de Markov Monte Carlo para mostrar la efectividad del método. Luego, realizamos un proyecto acerca de la aplicación del formalismo de la Robustez Interna a una compilación de datos de crecimiento cósmico, el cual es un método Bayesiano que potencialmente puede detectar outliers (datos aislados), errores sistemáticos o nuevas leyes físicas en los datos, considerando la posibilidad de que subconjuntos de los datos sigan diferentes parámetros o modelos (incluyendo de esta manera el aspecto de comparación de modelos básico de la estadística Bayesiana). No se encuentran errores sistemáticos ni outliers en el set de datos, así asegurando su robustez interna. Finalmente, tomamos por completo el campo de comparación de modelos Bayasiana, y lo hacemos via un estudio acerca de diferentes métodos de comparación de modelos cosmológicos. Se comparan varios modelos de energía oscura usando datos crecimiento cósmico y expansión cósmica, y esto se hace utilizando cuatro criterios de comparación: Comparación de evidencias, Criterio de Información Bayesiano, Criterio de Información de Akaike y un método reciente de Figura de Mérito. Luego, se discute acerca de la efectividad y conveniencia de cada uno de ellos.
CONICYT Powered@NLHPC: Esta tesis fue parcialmente apoyada por la intraestructura de supercómputo del NLHPC (ECM-02)
Durrive, Jean-Baptiste. "Baryonic processes in the large scale structuring of the Universe." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS346/document.
Повний текст джерелаMy thesis deals with two important topics of Cosmology:(i) Origin of cosmological magnetic fields:Magnetic fields seem ubiquitous in the Universe, present at all scales and all times, probably even in the entire intergalactic medium. Their origin is still unclear, especially on the largest scales. The current paradigm is that they were first generated with extremely weak strengths, and later amplified during structure formation. Because of turbulence, the fields we observe in galaxies and galaxy clusters lost their initial characteristics. However, in less dense regions such as cosmological filaments, sheets or voids, magnetic fields have evolved more mildly. Therefore, intergalactic magnetic fields may still possess a memory of the processes that generated them and hold the key to their origin. I developed analytically a detailed physical model of a natural astrophysical mechanism that generates intergalactic magnetic fields during the first billion year, namely at the time when first stars and galaxies were born. Then, in collaboration with H. Tashiro and N. Sugiyama (Japan), I computed analytically the mean energy density injected in the entire Universe through this mechanism. Independently, in collaboration with D. Aubert (France), I derived the topological and statistical properties of the magnetic field thus generated, using cosmological numerical simulations. This way I demonstrated that this simple, natural photoionization-based magnetogenesis must have created magnetic seed fields with properties a priori perfectly compatible with present day observations.(ii) Gravitational fragmentation of the cosmic web:Cosmological numerical simulations suggest that the Universe has a web-like structure, the nodes of which are galaxy clusters. These nodes are supplied with matter flowing along the filaments interconnecting them. Part of this accretion occurs intermittently, which indicates that clumps of matter form not only inside clusters themselves, but also either in cosmic voids, walls and/or filaments. I studied gravitational instability in stratified media in the frame of spectral theory, in planar and cylindrical geometries, relevant for cosmic walls and filaments, for isothermal, polytropic, and with and without an external gravitational background (e.g. Dark Matter). I have recasted the problem as an eigenvalue problem in the force operator formalism, and derived the wave equation governing the growth of perturbations. I also studied it in matrix form, which gives complementary information
Graham, Matthew James. "Large-scale structure of the early universe." Thesis, University of Central Lancashire, 1997. http://clok.uclan.ac.uk/21834/.
Повний текст джерелаPicard, Alain Mould Jeremy. "The large scale structure of the universe /." Diss., Pasadena, Calif. : California Institute of Technology, 1991. http://resolver.caltech.edu/CaltechETD:etd-09172008-084234.
Повний текст джерелаAlimi, 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.
Повний текст джерела