Letteratura scientifica selezionata sul tema "Cosmology"
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Articoli di riviste sul tema "Cosmology"
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Szalay, Alexander, John Peacock, Y. Chu L. da Costa, J. Einasto, G. Ellis, D. Koo, S. Lilly, et al. "Commission 47: Cosmology: (Cosmologie)." Transactions of the International Astronomical Union 24, no. 1 (2000): 311–14. http://dx.doi.org/10.1017/s0251107x00003242.
Testo completoAbstract (sommario):
Cosmology is one of the most dynamically evolving areas of astrophysics today. Twenty years ago the estimates of the amplitude of the primordial fluctuations were about 10-3, almost a factor of 100 off of today’s measurements. Ten years ago we could only hope for high precision measurements of large scale structure, there were less than 5000 redshifts measured, and only a handful of normal galaxies with z > 1 were known. Computer models of structure formation had just begun to consider non-power-law spectra based on physical models like hot/cold dark matter. As a consequence there was considerable freedom in adjusting parameters in the various galaxy formation scenarios. In contrast, many of today’s debates are about factors of 2 and soon we will be arguing about 10% differences. The Harrison-Zeldovich shape of the primordial fluctuation spectrum, first derived from philosophical arguments can now be quantified from detections of fluctuations by COBE. The number of available redshifts is beyond 50,000, and soon we will have redshift surveys surpassing 1 million galaxies. N-body simulations are becoming more sophisticated, of higher resolution, and incorporating complex gas dynamics.
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Setti, G., K. Satco, J. Audouze, G. de Vaucouleurs, J. E. Gunn, S. Hayakawa, L. Zhi Fang, et al. "Commission 47: Cosmology (Cosmologie)." Transactions of the International Astronomical Union 20, no. 1 (1988): 653–55. http://dx.doi.org/10.1017/s0251107x00007483.
Testo completoAbstract (sommario):
The number of pages allocated to the commission report has been very limited and certainly not sufficient to cover in any exhaustive manner the wide range of topics relevant to cosmology and to provide also extensive bibliographies. Because of the vast amount of material to be covered, the report is based on a number of contributions from different colleagues who have been asked to highlight the main trends in the triennium (mid 1984 - mid 1987), together with a list of references sufficiently comprehensive to serve as a guideline for further reading. Unfortunately, two of the expected contributions did not reach me in time for inclusion in the report, and consequently topics such as the large scale structure and streaming motions, the clusters of galaxies and the counts of extragalactic radio sources are not included. However, it is my understanding that a large portion, if not all, of these topics will be covered in the reports of Commissions 28 and 40, and if true, this will at least avoid unnecessary overlaps. It should also be mentioned here that several proceedings of very recent IAU conferences provide excellent, updated and exhaustive reviews of the research work relevant to cosmology.
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Partridge, R. B., V. Trimble, Bernard Fort, Matthew Colless, G. F. Smoot, J. C. Mather, and Bernard Sadoulet. "Commission 47: Cosmology (Cosmologie)." Transactions of the International Astronomical Union 22, no. 1 (1994): 539–64. http://dx.doi.org/10.1017/s0251107x00008312.
Testo completo
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Peacock, J. A., S. J. Lilly, G. Bruzual, L. Campusano, Y. Chu, L. DaCosta, J. Einasto, et al. "Commission 47: Cosmology: (Cosmologie)." Transactions of the International Astronomical Union 25, no. 1 (2002): 317–20. http://dx.doi.org/10.1017/s0251107x00001632.
Testo completo
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Desmet, Ronny. "La cosmologie de Whitehead [Whitehead’s Cosmology]." Process Studies 37, no. 2 (2008): 200–210. http://dx.doi.org/10.5840/process200837234.
Testo completo
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Verde, Licia. "Precision cosmology, Accuracy cosmology and Statistical cosmology." Proceedings of the International Astronomical Union 10, S306 (May 2014): 223–34. http://dx.doi.org/10.1017/s1743921314013593.
Testo completoAbstract (sommario):
AbstractThe avalanche of data over the past 10-20 years has propelled cosmology into the “precision era”. The next challenge cosmology has to meet is to enter the era of accuracy. Because of the intrinsic nature of studying the Cosmos and the sheer amount of data available now and coming soon, the only way to meet this challenge is by developing suitable and specific statistical techniques. The road from precision Cosmology to accurate Cosmology goes through statistical Cosmology. I will outline some open challenges and discuss some specific examples.
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Steele, Craig. "Cosmology." Journal of Humanistic Mathematics 9, no. 1 (January 2019): 368. http://dx.doi.org/10.5642/jhummath.201901.26.
Testo completo
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Silk, Joseph. "Cosmology." Classical and Quantum Gravity 25, no. 22 (November 4, 2008): 229003. http://dx.doi.org/10.1088/0264-9381/25/22/229003.
Testo completo
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Börner, G. "Cosmology." European Physical Journal Special Topics 152, no. 1 (December 2007): 139–81. http://dx.doi.org/10.1140/epjst/e2007-00380-7.
Testo completo
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Spyridon, Melas. "A Selection of Gemstones: Elements of Akbarian Cosmology." Islamovedenie 14, no. 1 (June 1, 2023): 86–98. http://dx.doi.org/10.21779/2077-8155-2023-14-1-86-98.
Testo completoAbstract (sommario):
The author notes that the Sufi theological tradition of Akbariya was formed on the basis of the works by Muhyiddin ibn Arabi. Part of this tradition is the doctrine of the nature of the world and its creation, i.e. cosmology. The purpose of the article is to reveal some elements of Akbarian cosmology. The semantic content of the concepts of Akbarian cosmology, creation and approved incarnations is determined. The author maintains that, although things exist eternally, from time immemorial and without beginning in divine knowledge precisely in the form of approved incarnations, at the same time they do not exist. The shortcomings of the (neo)platonic interpretation of the approved incarnations are demonstrated. The difference between Akbariya and the Academy of Plato lies in the fact that the teaching of the first concerns a person and his heart as an organ of self-integrity and connection with God, while the teaching of the second concerns the rational part of the soul. Also, several aspects of the cosmological concept of the Divine Names are revealed, the problem of the pantheistic interpretation of this theory is discussed and it is proved that it is not justified by the texts of Ibn Arabi. The cosmologi-cal meaning of the image of the mirror and the epistemological meaning of the image of “the silence of those who know” are also revealed. The last “gem” – the Perfect Man – is the beginning, the end and the preservation of creation. Various aspects of the concept of the Perfect Man (ethical and cosmologi-cal), its identification with Adam, with humanity in general and with Muhammad (the reality of Mu-hammad) are considered, the question of the “hypostasy” of the Perfect Man is identified and discussed
Tesi sul tema "Cosmology"
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Pocino, Yuste Andrea. "Cosmology with photometric redshift." Doctoral thesis, Universitat Autònoma de Barcelona, 2020. http://hdl.handle.net/10803/671733.
Testo completoAbstract (sommario):
Els cartografiats de galàxies fotomètrics actuals i futurs observaran un gran volum de l’univers que ens permetrà acotar amb precisió el model cosmològic. Tanmateix, la capacitat de delimitar el model que tenen aquests cartografiats a través de les sondes cosmològiques depèn de la precisió i certesa amb les que es determina el redshift de les galàxies. Per tant, la determinació del redshift fotomètric i els seus efectes en les anàlisis cosmològiques han de ser tractats i estudiats curosament.
En la primera part de la tesi, transformem la fotometria de simulacions que ja existeixen per imitar les mesures fotomètriques del Dark Energy Survey (DES). D’aquesta manera, esperem recuperar la distribució real del redshift fotomètric en simulacions, i així crear una base encara més realista per comprovar els resultats de les anàlisis cosmològiques de DES que fan us del redshift fotomètric. Per transformar les simulacions utilitzem diversos mètodes que transfereixen les propietats estadístiques de la fotometria d’observacions real a les simulacions.
A la segona part de la tesi, utilitzem la tècnica del Self-Organizing Map per seleccionar galàxies per ser observades amb espectroscòpia, contribuint així al projecte C3R2 que vol establir un mapa correlacional entre l’espai de colors i redshift i omplir-ho amb informació espectroscòpica. En aquesta part també explorem l’espai de colors definit per la fotometria del Physics of the Accelerating Universe Survey (PAUS) per tal d’estudiar la cobertura del redshift espectroscòpic del seu espai de colors. Volem determinar la quantitat d’espai de color sense cobertura espectroscòpica perquè la falta de representació d’espectroscòpia pot ser una font de biaix quan la precisió dels redshifts fotomètrics és avaluada comparant-los amb redshifts espectroscòpics o quan els redshifts espectroscòpics s’utilitzen com a mostra d’entrenament per determinar els redshifts fotomètrics amb algoritmes d’entrenament.
Finalment, explorem com la variació en la profunditat de les observacions des de terra combinades amb les d’Euclid afecta la precisió dels redshifts fotomètrics i, per tant, la capacitat de determinar els paràmetres cosmològics d’Euclid sobretot quan utilitza galaxy clustering i galaxy-galaxy lensing com a sondes cosmològiques. També estudiem com la densitat de les mostres de galàxies afecta la capacitat de delimitar els paràmetres cosmològics i quina és la configuració de bins tomogràfics de redshift que permet extreure la màxima informació per delimitar els paràmetres cosmològics. Per tal de dur a terme aquesta anàlisi, creem diverses distribucions realistes de redshift fotomètric basades en la simulació Flagship d’Euclid i utilitzem el formalisme de Fisher per fer una estimació de la capacitat d’acotament dels paràmetres cosmològics de les diferents configuracions de les mostres de galàxies.<br>Los cartografiados de galaxias fotométricos actuales y futuros observarán un gran volumen del universo que nos permitirá acotar con precisión el modelo cosmológico. Aun así, la capacidad de los cartografiados para delimitar el modelo a través de las sondas cosmológicas depende de la precisión y certeza con las que se determina el redshift de las galaxias. Por lo tanto, la determinación del redshift fotométrico y sus efectos en los análisis cosmológicos deben ser tratados y estudiados cuidadosamente.
En la primera parte de la tesis, transformamos la fotometría de simulaciones que ya existen para imitar las mediciones fotométricas del Dark Energy Survey (DES). De esta forma, esperamos recuperar la distribución real del redshift fotométrico en simulaciones, y así crear una base aún más realista para comprobar los resultados de los análisis cosmológicos de DES que usan redshifts fotométricos. Para transformar las simulaciones utilizamos diversos métodos que transfieren las propiedades estadísticas de la fotometría de observaciones reales a las simulaciones.
En la segunda parte de la tesis, utilizamos la técnica del Self-Organizing Map para seleccionar galaxias para ser observadas con espectroscopia, contribuyendo así al proyecto C3R2 que quiere establecer un mapa correlacional entre el espacio de colores y redshift y llenarlo con información espectroscópica. En esta parte también exploramos el espacio de colores definido por la fotometría del Physics of the Accelerating Universe Survey (PAUS) con tal de estudiar la cobertura del redshift espectroscópico de su espacio de colores. Queremos determinar la cantidad del espacio de color sin cobertura espectroscópica porque la falta de representación espectroscópica puede originar un sesgo cuando la precisión del redshift fotométrico se evalúa comparándolo con el redshift espectroscópico o cuando el redshift espectroscópico se utiliza como muestra de entrenamiento para determinar el redshift fotométrico con algoritmos de entrenamiento.
Finalmente, exploramos como la variación en la profundidad de las observaciones desde tierra combinadas con las de Euclid afecta la precisión de los redshifts fotométricos y, por lo tanto, la capacidad de Euclid para determinar los parámetros cosmológicos sobre todo cuando se utilizan galaxy clustering y galaxy-galaxy lensing como sondas cosmológicas. También estudiamos como la densidad de las muestras de galaxias afecta la capacidad de acotar los parámetros cosmológicos y cuál es la configuración de bines tomográficos de redshift que permiten extraer la máxima información para delimitar los parámetros cosmológicos. Para llevar a cabo este análisis, creamos diversas distribuciones realistas de redshift fotométrico basadas en la simulación Flagship de Euclid y utilizamos el formalismo de Fisher para hacer una estimación de la capacidad de acotar los parámetros cosmológicos de las diferentes configuraciones de las muestras de galaxias.<br>Current and future photometric surveys will observe a large volume of the universe that will allow us to accurately constrain the cosmological model. However, the constraining power from cosmological probes of photometric surveys highly relies on the accuracy and precision with which we can determine the galaxies redshifts. Therefore, the determination of photometric redshifts (photo-zs) and their effect in cosmological analysis should be treated and studied carefully.
In the first part of this thesis, we transform the photometry of existing simulations to mimic the photometric measurements of the Dark Energy Survey (DES). With this exercise, we expect to recover the real photo-z distribution in simulations, thus creating a more realistic environment to crosscheck the performance of DES in cosmological analyses that use photo-z. We transform the simulations using several method to transfer the statistical properties from the real observations photometry to the simulations.
In the second part of the thesis, we use the Self-Organizing Map technique to select spectroscopic targets for the C3R2 program aimed at establishing the mapping between color and redshift space. We also explore the color space defined by the photometry of galaxies from the Physics of the Accelerating Universe Survey (PAUS) in order to study the spectroscopic redshift coverage of its color space. We want to quantify the regions of color space without spectroscopic redshifts because the lack of spectroscopic representation can be a source of bias when the accuracy of photo-zs is evaluated by comparing it to spectroscopic redshifts and when the spectroscopic redshifts are used to determine the photo- z with training-based algorithms.
Lastly, we explore how the variation of the depth of ground-based observations combined with Euclid observations affects the accuracy and precision of the photo-z and thus the cosmological constraining power of Euclid focusing on photometric galaxy clustering and galaxy-galaxy lensing analyses. We also study how the number density of photometric galaxy samples affects the constraining power and which tomographic redshift binning configuration returns the maximum information to constrain the cosmological parameters. To perform such analyses, we create several realistic photo-z distributions based on the Euclid Flagship simulation and we use the Fisher forecast and the cosmological inference code, CosmoSIS, over the different configurations of the galaxy samples to determine the cosmological constraining power.<br>Universitat Autònoma de Barcelona. Programa de Doctorat en Física
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Manera, Miret Marc. "Cosmologia i Formació d'Estructures / Cosmology and Structures Formation." Doctoral thesis, Universitat de Barcelona, 2007. http://hdl.handle.net/10803/1790.
Testo completoAbstract (sommario):
In this thesis we push forward techniques to learn about the large scale structure formation of the universe. The approach is from theory, observations and simulations. From theory we study the growth of four non standard cosmological models: DGP model, Cardassian model, Chaplygin gas model and Coupled Quintessence model. From observations we look at the ISW effect by means of the cross-correlation between CMB maps and galaxy survey. From a compilation of data we contrain the cosmological parameters and give new evidence of dark energy. We also introduce a new method to compute errors in configuration space and compare it with other methods in the literature. This method takes into account the geometry of the suveys and it is shown to give accurate results at large angles. In this thesis we also use large dark matter simulations to study the clustering and the local halo bias model. KEY WORDS: large scale structure, structure formation, dark energy, halo bias<br><I>CATALÀ:<br/><br/>En aquesta tesi estudiem la formació d'estructures a gran escala de l'univers apoximant-nos-hi des de la teoria, les observacions i les simulacions. Respecte la teoria estudiem el creixement d'estructures en quatre models no estàndards: el model DGP, el model Cardassian, el model de gas de Chaplygin i el model de Quintessècia acoplada. <br/>De les observacions estudiem la formació d'estructura a partir de correlacions entre mapes de galàxies amb mapes del CMB, les quals mesuren l'efecte ISW. A partir d'una compilació que d'aquestes mesures restringim els paràmetres cosmològics i mostrem nova evidència de l'energia fosca. També introduim un nou mètode per a calcular els errors de les correlacions en l'espai de configuració. Comparem aquest mètode amb d'altres i mostrem que estima bé els errors a angles grans, doncs tenim en compte l'area del cel observada. Finalment utilitzem simulacions de matéria fosca per estudiar el clustering i el model de bias local. </i><br>RESUMEN CASTELLANO:<br/><br/>En esta tesis estudiamos la formación de estructura en el universo en las vertientes teórica, observacional y con simulaciones. Respeto a la teoria estudiamos el crecimiento de estructuras en cuatro modelos no estándares: el modelo DGP, el modelo Cardassian, el modelo de gas de Chaplygin y el modelo de Quintessencia acoplado. Respecto a las observaciones estudiamos la formación de estructura a partir de las correlaciones entre el CMB y mapas de galaxias, las cuales miden el efecto ISW. A partir de una compilación de estas medidas restringimos los parámetros cosmológicos dando nueva evidencia de la energía oscura. También introducimos un nuevo método para el cálculo de errores en espacio de configuración y mostramos, al compararlo con otros, que estima bien los errores a grandes ángulos puesto que tenemos en cuenta la geometria de área observada. Finalmente, utilizando simulaciones de materia oscura, estudiamos el clustering y el modelo de bias local. PALABRAS CLAVE: Estructura a gran escala, energia oscura, bias en halos, formación de estructura.
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Gatti, Marco. "Weak lensing in DES Y3: redshift distributions, shape catalogue, and mass mapping." Doctoral thesis, Universitat Autònoma de Barcelona, 2020. http://hdl.handle.net/10803/670527.
Testo completoAbstract (sommario):
En aquesta tesi hem tractat alguns aspectes clau de les lents dèbils gravitacionals en el context d’enquestes fotomètriques. En particular, es van utilitzar simulacions i dades preses durant els primers tres anys d’observacions de l’enquesta de l’energia fosca (DES Y3). Les programacions de DES estan publicades a finals d’aquest any amb les principals anàlisis cosmològiques de DES Y3 i aquesta tesi abasta algunes de les anàlisis. A la part II d’aquesta tesi, ens hem centrat en la tècnica de “clustering-redshift” i el seu part en la principal estratègia de calibració de redshift DES Y3. Clustering-redshift és un mètode per obtenir (o calibrar) distribucions redshift que es basa en correlacions creuades amb mostres petites amb redshift segurs. La part III es va dedicar a la prova del catàleg oficial de formes DES Y3, que abasta ~ 4143 dòlars ^ 2 de l’hemisferi sud i que comprèn ~ 100 milions de galàxies, cosa que el converteix efectivament en el catàleg de formes més gran mai creat. A la darrera part de la tesi (capítols 6 i 7), es van presentar els mapes de massa de lents febles amb lents febles DES Y3 i es va discutir una possible aplicació cosmològica dels mapes. En particular, vam introduir al capítol 6 quatre tècniques de reconstrucció massiva de mapes massius diferents, cadascuna d’elles que assumeixen diferents nivells en el camp de convergència recuperat. El capítol 7 presentava una anàlisi de cosmologia simulada utilitzant el segon i el tercer moment dels mapes de massa de lent feble, dirigits a les dades de DES Y3.<br>En esta tesis hemos estudiado algunos aspectos clave de la lente gravitacional débil en el contexto de los estudios fotométricos. En particular, utilizamos simulaciones y datos tomados durante los primeros tres años de observaciones de la Dark Energy Survey (DES Y3). DES está programado para lanzar su análisis cosmológico principal DES Y3 más adelante este año, y esta tesis cubre algunas partes del análisis. En la Parte II de esta tesis, nos hemos centrado en la técnica de “clustering redshift’’ y su parte en la estrategia principal de calibración del desplazamiento al rojo de DES Y3. El clustering redshift es un método para obtener (o calibrar) distribuciones de desplazamiento al rojo que se basa en correlaciones cruzadas con muestras pequeñas con desplazamiento al rojo seguro. La Parte III se dedicó a la prueba del catálogo oficial de formas de lente gravitacionales de DES Y3, que abarca ~ 4143 $ deg ^ 2 del hemisferio sur y comprende ~ 100 millones de galaxias, lo que lo convierte en el catálogo de formas más grande jamás creado. En la última parte de la tesis (Capítulo 6 y 7), presentamos los mapas oficiales de masa de lentes débiles de DES Y3, y discutimos una posible aplicación cosmológica de los mapas. En particular, introdujimos en el Capítulo 6 cuatro técnicas diferentes de reconstrucción de mapas de masas, cada una de las cuales asumió diferentes antecedentes en el campo de convergencia recuperado. El Capítulo 7 presentó un análisis de cosmología simulada utilizando el segundo y el tercer momento de los mapas de masas de lentes débiles, dirigidos a los datos DES Y3.<br>In this thesis we have addressed some key aspects of gravitational weak lensing in the context of photometric surveys. In particular, we used simulations and data taken during the first three years of observations of the Dark Energy Survey (DES Y3). DES is scheduled to release their main DES Y3 cosmological analysis later this year, and this thesis covers some parts of the analysis. In Part II of this thesis, we have focused on the “clustering-redshift’’ technique and its role in the main DES Y3 redshift calibration strategy. Clustering-redshift is a method to obtain (or calibrate) redshift distributions which is based on cross-correlations with small samples with secure redshifts. Part III was devoted to the testing of the official DES Y3 shape catalogue, covering ~ 4143$ deg^2 of the southern hemisphere and comprising ~100 million galaxies, which effectively makes it the largest shape catalogue ever created. In the last part of the thesis (Chapter 6 & 7), we presented the official DES Y3 weak lensing mass maps, and discussed a potential cosmological application of the maps. In particular, we introduced in Chapter 6 four different mass map reconstruction techniques, each of those assuming different priors on the recovered convergence field. Chapter 7 presented a simulated cosmology analysis using the second and third moments of the weak lensing mass maps, targeted at the DES Y3 data.
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Hasselfield, Matthew. "Galaxy cluster cosmology with the Atacama Cosmology Telescope." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/45602.
Testo completoAbstract (sommario):
Observations of the Cosmic Microwave Background (CMB) are crucial components of our understanding of cosmology. Modern high resolution, ground-based CMB survey instruments provide important information about the mass and energy content of our present Universe and the high-energy physics of the Big Bang.
In this work we present several aspects of our work on the Atacama Cosmology Telescope (ACT), a 6m telescope in Northern Chile that observed the CMB in three millimetre wavelength bands from 2007–2010. We begin with a description of the Multi-Channel Electronics readout system, an important component of the data acquisition systems for ACT and several other CMB observatories. The system provides room-temperature electronics and software for controlling and reading out arrays of Transition Edge Sensor bolometers via a cryogenic time-domain multiplexing system.
We next present our measurement of the ACT point spread function, or beam, using observations of Solar System planets. An accurate understanding of the beam and its covariant error is essential for interpretation of astrophysical and cosmological signal in the ACT data. We then use our understanding of the beam and the instrument calibration to measure the brightness temperatures of Uranus and Saturn at millimetre wavelengths. Precise measurements of planetary brightnesses provide convenient calibration sources for other observatories at these wavelengths.
Finally we present a sample of galaxy clusters detected in the ACT maps. We develop a new approach for the analysis of Sunyaev-Zeldovich signal that incorporates a model for the typical cluster pressure to better understand selection effects and evaluate cluster masses. Addressing the current level of systematic uncertainty in the overall mass calibration of clusters, we explore the cosmological constraints obtained when calibrating the mass relation based on pressure profile measurements from X-ray data and from models that take different approaches to the cluster physics. Ultimately we use dynamical mass estimates based on optical velocity dispersion measurements to obtain constraints on the amplitude of scalar fluctuations, the matter density, the Dark Energy equation of state parameter, and the sum of the neutrino mass species.
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Leta, Carlos Pereira. "Formação de estruturas em cosmologia no regime não-linear: uma aproximação por sistemas dinâmicos." Universidade do Estado do Rio de Janeiro, 2006. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=560.
Testo completoAbstract (sommario):
Conselho Nacional de Desenvolvimento Científico e Tecnológico<br>Formação de estruturas em larga escala é um problema em aberto em Cosmologia. Há um consenso de que a variedade de estruturas observadas tais como galáxias e aglomerados de galáxias tiveram origem a partir de pequenas flutuações do fluido cósmico possivelmente geradas durante a época inflacionária na era dominada pela matéria. Os estágios iniciais da evolução destas flutuações são descritas pela teoria de Jeans resultante da aproximação linear das equações hidrodinâmicas. Basicamente, a instabilidade devido à ação do campo gravitacional induz à existência de dois tipos de modos perturbativos: os modos instáveis que crescem, e os estáveis que oscilam como ondas sonoras. A distinção entre estes modos depende se o comprimento de onda de um determinado modo perturbativo é maior ou menor que um comprimento de onda típico conhecido como o comprimento de Jeans. Eventualmente, o crescimento dos modos instáveis quebra a aproximação e efeitos não-lineares tornam-se cruciais para a formação de estruturas. Neste sentido, nosso objetivo é estudar o problema não-linear de formação de estruturas em um Universo em expansão dominado pela matéria considerando uma extensão consistente da teoria linear de Jeans. Uma aproximação por sistema dinâmico é fornecida pelo método de Galerkin usado para integrar as equações dinâmicas do fluido auto-graviante. Conseqüentemente é exibido o comportamento dos modos perturbativos instáveis e estáveis do fluido cósmico além do regime linear anterior à formação de estruturas. Nós também consideramos consistentemente a influência da viscosidade ao invés de introduzi-la de um modo artificial como no modelo de Adesão.<br>The formation of large scale structure is an outstanding problem in Cosmology. It is a consensus that the observed variety of structures such as galaxies and clusters of galaxies have originated from small fluctuations of the cosmic fluid possibly generated during the inflationary epoch-in the matter dominated era. The early stages of evolution of these fluctuations are described by the Jeans theory resulting from the linear approximation of the hydrodynamical equations. Basically, the instabilities due the action of the gravitational field induce the existence of two types of perturbativo modes: the unstable modes that grow, and the stable one that oscillate as sound waves. The distinction between these modes depend son whether the wave length of a given perturbativo mode is greater or smaller than atypical wave-length known as the Jeans length. Eventually, the growth of the unstable modes breaks the linear approximation and nonlinear effects turn out to be crucial for the formation of structures. In this vein, our objective here is to study the problem of nonlinear structure formation in a matter dominated expanding universe considering a consistent extension of the linear Jeans theory. A dynamical system approach is provided by the Galerkin method used to integrate the self-gravitating fluid dynamical equations. Therefore, the behavior of the unstable and stable perturbative modes of the cosmic fluid are exhibited beyond the linear regime prior the formation of structures. We have also considered the influence of viscosity consistently rather than introducing it in an artificial way as in the Adhesion Model.
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Bonilla, Tobar Maria del Pilar. "Reaquecimento em um modelo de inflação quintessencial /." São Paulo, 2009. http://hdl.handle.net/11449/132544.
Testo completoAbstract (sommario):
Orientador: Rogério Rosenfeld<br>Banca: Bruto Max Pimentel Escobar<br>Banca: Rudnei de Oliveira Ramos<br>Resumo: O modelo cosmológico inflacionário postula uma rápida expansão do universo primordial, denominada inflação, que pode resolver certas diflculdades da cosmologia padrão. Em modelos inflacionários mais simples a expansão acelerada é causada pela densidade de energia armazenada em um campo escalar denominado inflaton. Após a fase inflacionária, o universo encontra-se em um estado frio e sem partículas. Deve haver um mecanismo responsável pelo reaquecimento do universo. Nesta dissertação, primeiramente fazemos uma revisão simples da cosmologia padrão e inflacionária. Posterior mente, realizamos um estudo detalhado de três diferentes processos de reaquecimento: ressonância paramétrica, instabilidades taquiônicas e reaquecimento perturbativo. Finalmente, fazemos uma análise deste processo para um modelo de inflação quintessencial usando o programa LATTICEEASY<br>Abstract: The inflationary cosmological model postulates a fast expansion of the eaxly universe, called inflation, which can solve some issues of the standard cosmological model. In simple inflationary models the accelerated expansion is caused by the energy density stored in a scalar field called inflaton. After the inflationary phase, the universe is in a cold state and without particles. There must be a mechanism responsable for its reheating. In this dissertation we flrstly review the standard and inflationary cosmologies. We then perform a detailed study of three different reheating processes: parametric ressonance, tachyonic instabilities and perturbative reheating. Finally, we mahe an analysis of this process for a quintessencial inflation model using the program LATTICEEASY<br>Mestre
7
Knebe, Alexander. "Computational cosmology." Thesis, Universität Potsdam, 2008. http://opus.kobv.de/ubp/volltexte/2010/4114/.
Testo completoAbstract (sommario):
“Computational Cosmology” is the modeling of structure formation in the Universe by means of numerical simulations. These simulations can be considered as the only “experiment” to verify theories of the origin and evolution of the Universe. Over the last 30 years great progress has been made in the development of computer codes that model the evolution of dark matter (as well as gas physics) on cosmic scales and new research discipline has established itself.
After a brief summary of cosmology we will introduce the concepts behind such simulations. We further present a novel computer code for numerical simulations of cosmic structure formation that utilizes adaptive grids to efficiently distribute the work and focus the computing power to regions of interests, respectively. In that regards we also investigate various (numerical) effects that influence the credibility of these simulations and elaborate on the procedure of how to setup their initial conditions. And as running a simulation is only the first step to modelling cosmological structure formation we additionally developed an object finder that maps the density field onto galaxies and galaxy clusters and hence provides the link to observations.
Despite the generally accepted success of the cold dark matter cosmology the model still inhibits a number of deviations from observations. Moreover, none of the putative dark matter particle candidates have yet been detected. Utilizing both the novel simulation code and the halo finder we perform and analyse various simulations of cosmic structure formation investigating alternative cosmologies. These include warm (rather than cold) dark matter, features in the power spectrum of the primordial density perturbations caused by non-standard inflation theories, and even modified Newtonian dynamics. We compare these alternatives to the currently accepted standard model and highlight the limitations on both sides; while those alternatives may cure some of the woes of the standard model they also inhibit difficulties on their own.
During the past decade simulation codes and computer hardware have advanced to such a stage where it became possible to resolve in detail the sub-halo populations of dark matter halos in a cosmological context. These results, coupled with the simultaneous increase in observational data have opened up a whole new window on the concordance cosmogony in the field that is now known as “Near-Field Cosmology”. We will present an in-depth study of the dynamics of subhaloes and the development of debris of tidally disrupted satellite galaxies.1 Here we postulate a new population of subhaloes that once passed close to the centre of their host and now reside in the outer regions of it. We further show that interactions between satellites inside the radius of their hosts may not be negliable. And the recovery of host properties from the distribution and properties of tidally induced debris material is not as straightforward as expected from simulations of individual satellites in (semi-)analytical host potentials.<br>Die Kosmologie ist heutzutage eines der spannendsten Arbeitsgebiete in der Astronomie und Astrophysik. Das vorherrschende (Urknall-)Modell in Verbindung mit den neuesten und präzisesten Beobachtungsdaten deutet darauf hin, daß wir in einem Universum leben, welches zu knapp 24% aus Dunkler Materie und zu 72% aus Dunkler Energie besteht; die sichtbare Materie macht gerade einmal 4% aus. Und auch wenn uns derzeit eindeutige bzw. direkte Beweise für die Existenz dieser beiden exotischen Bestandteile des Universums fehlen, so ist es uns dennoch möglich, die Entstehung von Galaxien, Galaxienhaufen und der großräumigen Struktur in solch einem Universum zu modellieren. Dabei bedienen sich Wissenschaftler Computersimulationen, welche die Strukturbildung in einem expandierenden Universum mittels Großrechner nachstellen; dieses Arbeitsgebiet wird Numerische Kosmologie bzw. “Computational Cosmology” bezeichnet und ist Inhalt der vorliegenden Habilitationsschrift.
Nach einer kurzen Einleitung in das Themengebiet werden die Techniken zur Durchführung solcher numerischen Simulationen vorgestellt. Die Techniken zur Lösung der relevanten (Differential-)Gleichungen zur Modellierung des “Universums im Computer” unterscheiden sich dabei teilweise drastisch voneinander (Teilchen- vs. Gitterverfahren), und es werden die verfahrenstechnischen Unterschiede herausgearbeitet. Und obwohl unterschiedliche Programme auf unterschiedlichen Methoden basieren, so sind die Unterschiede in den Endergebnissen doch (glücklicherweise) vernachlässigbar gering. Wir stellen desweiteren einen komplett neuen Code – basierend auf dem Gitterverfahren – vor, welcher einen Hauptbestandteil der vorliegenden Habilitation darstellt.
Im weiteren Verlauf der Arbeit werden diverse kosmologische Simulationen vorgestellt und ausgewertet. Dabei werden zum einen die Entstehung und Entwicklung von Satellitengalaxien – den (kleinen) Begleitern von Galaxien wie unserer Milchstraße und der Andromedagalaxie – als auch Alternativen zum oben eingeführten “Standardmodell” der Kosmologie untersucht. Es stellt sich dabei heraus, daß keine der (hier vorgeschlagenen) Alternativen eine bedrohliche Konkurenz zu dem Standardmodell darstellt. Aber nichtsdestoweniger zeigen die Rechnungen, daß selbst so extreme Abänderungen wie z.B. modifizierte Newton’sche Dynamik (MOND) zu einem Universum führen können, welches dem beobachteten sehr nahe kommt.
Die Ergebnisse in Bezug auf die Dynamik der Satellitengalaxien zeigen auf, daß die Untersuchung der Trümmerfelder von durch Gezeitenkräfte zerriebenen Satellitengalaxien Rückschlüsse auf Eigenschaften des ursprünglichen Satelliten zulassen. Diese Tatsache wird bei der Aufschlüsselung der Entstehungsgeschichte unserer eigenen Milchstraße von erheblichem Nutzen sein. Trotzdem deuten die hier vorgestellten Ergebnisse auch darauf hin, daß dieser Zusammenhang nicht so eindeutig ist, wie er zuvor mit Hilfe kontrollierter Einzelsimulationen von Satellitengalaxien in analytischen “Mutterpotentialen” vorhergesagt wurde: Das Zusammenspiel zwischen den Satelliten und der Muttergalaxie sowie die Einbettung der Rechnungen in einen kosmologischen Rahmen sind von entscheidender Bedeutung.
8
Narimani, Ali. "Dimensionless cosmology." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/37365.
Testo completoAbstract (sommario):
The variability of fundamental physical constants has been a topic of interest both
theoretically and experimentally for many years. Although it is interesting to investigate the consequences of such a variation, it is important to realise that only
the variation of dimensionless combination of constants can be meaningfully measured and discussed. In this thesis, I try to justify this way of thinking and apply
it to two basic cosmological observables, Big Bang Nucleosynthesis and Cosmic
Microwave Background anisotropies. I will mention some related studies that are
either wrong or not complete because of being dimensionful.
Variation of constants could be considered on two different levels. On the first
level one assumes that the constants are time invariant but they can assume different
values in different Universes or patches of sky. A thought experiment describing
a discussion with aliens having a different system of units with different coupling
constants could be helpful, this idea will be returned to throughout the thesis. On
the next level, the constants can be promoted to being smooth functions of time or
space. It is good to have a firm understanding of what happens on the previous level
before trying to consider genuinely variable constants. For variable constants we
need to consider theories beyond the currently accepted ones, which are capable of
consistently describing such a variation.
I briefly review the scalar-tensor theory of gravity as a possible way to describe
the variation of the gravitational coupling. I give a brief historical review on the
subject and consider the theory in the two so called ‘frames’, discussing about the
benefits of each frame mathematically and the physical meaning of these frames.
Such theories could form the frame work in which further study of variable con-
stants could be carried out.
9
Whiting, Alan B. "Local cosmology." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360010.
Testo completo
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Simon-Petit, Alicia. "Systèmes Dynamiques Gravitationnels." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLY021/document.
Testo completoAbstract (sommario):
L'histoire séculaire des systèmes dynamiques puise ses originesdansle développement du cadre mathématique en astronomie.L'objet de cette thèse est l'étude de propriétés de la gravitation de ce point de vue de la dynamiqueà différentes échelles cosmologiques.Dans la théorie du potentiel, l'isochronie définit généralement le mouvement d'oscillation harmonique de pendules.En 1959, le mathématicien et astronome Michel Hénon étend cette définition afin de caractériser les oscillationsorbitales d'étoiles, autour du centre du système à symétrie sphérique auquel elles appartiennent.Dans ce cas, la période d'oscillation peut dépendre de l'énergie de l'étoile.Aujourd'hui, son potentiel isochrone est majoritairement utiliséen simulation numérique pour ses propriétés analytiques d'intégrabilité, mais demeure par ailleurs souvent méconnu.Dans cette thèse, nous revisitons la caractérisation géométrique de l'isochronie comme initiée par Michel Hénon etcomplétons ainsi la famille des potentiels isochrones en physique. La classification de cet ensemblesous l'action de divers groupes mathématiques met en évidence une relation privilégiéeentre les isochrones.Nous montrons alors la nature keplérienne intrinsèque aux isochrones, laquelle est au coeur dela nouvelle relativité isochrone que nous présentons.Les conséquences de cette relativité en mécanique céleste, à savoirla généralisation de la troisième loi de Kepler, celle de la transformation de Bohlin ou Levi-Civita,et le théorème de Bertrand, conduisent à l'analyse du résultat d'un effondrement gravitationnel.Une analyse isochrone est développée pour caractériser un état de quasi-équilibredesystèmes auto-gravitants isolés, comme certains amas stellaires ou galaxies dynamiquement jeunes,à partir de propriétés orbitales de leurs étoiles ou contenu physique.A l'échelle cosmologique, la dynamique de l'univers dépendde sa composition énergétique. Elle peut s'exprimer sous forme d'unsystème dynamique conservatif, bien connu en écologie pour décrire la dynamiquede populations variées. Ce modèle dit de Lotka-Volterra est exploité pour décrireun espacetemps globalement homogène et isotrope, dont les composantes peuventêtre en interaction non uniquement gravitationnelle.Dans cet univers jungle, des comportements dynamiques effectifs à grande échelle pourraient conduire à une expansionaccélérée de l'univers sans nécessité d'énergie noire<br>Dynamical systems have a centuries-long history with roots going back to the mathematical development for astronomy. In the modern formalism, the present thesis investigates dynamical properties of gravitation at different astrophysical or cosmological scales.In potential theory, isochrony often refers to harmonic oscillations of pendulums. In 1959, the mathematician and astronomer Michel Hénon introduced an extended definition of isochrony to characterize orbital oscillations of stars around the center of the system to which they belong. In that case, the period of oscillations can depend on the energy of the star. Today, Michel Hénon’s isochrone potential is mainly used for its integrable property in numerical simulations, but is not widely known. In this thesis, we revisit his geometrical characterization of isochrony and complete the family of isochrone potentials in physics. The classification of this family under different mathematical group actions highlights a particular relation between the isochrones. The actual Keplerian nature of isochrones is pointed out and stands at the heart of the new isochronerelativity, which are presented together.The consequences of this relativity in celestial mechanics — a generalization of Kepler’sThird law, Bohlin or Levi-Civita transformation, Bertrand’s theorem — are applied to analyze the result of a gravitational collapse. By considering dynamical orbital properties, an isochrone analysis is developed to possibly characterize a quasi-stationary state of isolated self-gravitating systems, such as dynamically young stellar clusters or galaxies.At a cosmological scale, the dynamics of the universe depends on its energy content. Its evolution can be expressed as an ecological dynamical system, namely a conservative generalized Lotka-Volterra model. In this framework of a spatially homogeneous and isotropic spacetime, named Jungle Universe, the dynamical impact of a non-gravitational interaction between the energy components is analyzed. As a result, effective dynamical behaviors could account for an accelerated expansion of the universe without dark energy
Libri sul tema "Cosmology"
1
Contopoulos, Georgios, and Dimitrios Kotsakis. Cosmology. Berlin, Heidelberg: Springer Berlin Heidelberg, 1987. http://dx.doi.org/10.1007/978-3-642-71464-1.
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2
Bondi, Hermann. Cosmology. 2nd ed. Mineola, N.Y: Dover Publications, 2010.
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3
Hermann, Bondi. Cosmology. 2nd ed. Mineola, N.Y: Dover Publications, 2010.
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4
Hermann, Bondi. Cosmology. 2nd ed. Mineola, N.Y: Dover Publications, 2010.
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5
Liebscher, Dierck-Ekkehard. Cosmology. Berlin, Heidelberg: Springer Berlin Heidelberg, 2005. http://dx.doi.org/10.1007/b100199.
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Hetherington, Norriss S. Cosmology. Boca Raton: CRC Press, 2023. http://dx.doi.org/10.1201/9781003418047.
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Narlikar, Jayant Vishnu. Introduction to cosmology. 2nd ed. Cambridge [England]: Cambridge University Press, 1993.
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10
Davis, Andrew M., Maria-Teresa Teixeira, and Wm Andrew Schwartz, eds. Process Cosmology. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-81396-3.
Testo completoCapitoli di libri sul tema "Cosmology"
1
McNally, Derek. "Cosmology(Cosmologie)." In Reports on Astronomy, 561–80. Dordrecht: Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3364-7_34.
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2
Karttunen, Hannu, Pekka Kröger, Heikki Oja, Markku Poutanen, and Karl Johan Donner. "Cosmology." In Fundamental Astronomy, 371–90. Berlin, Heidelberg: Springer Berlin Heidelberg, 2003. http://dx.doi.org/10.1007/978-3-662-05333-1_19.
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3
Setti, G., K. Sato, J. Audouze, G. de Vaucouleurs, J. E. Gunn, S. Hayakawa, L. Zhi Fang, et al. "Cosmology." In Reports on Astronomy, 653–70. Dordrecht: Springer Netherlands, 1988. http://dx.doi.org/10.1007/978-94-009-2981-4_36.
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4
Fuller, Robert. "Cosmology." In Religion in American History, 190–209. Oxford, UK: Wiley-Blackwell, 2010. http://dx.doi.org/10.1002/9781444315806.ch10.
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5
Lofton, Kathryn. "Cosmology." In Religion in American History, 266–84. Oxford, UK: Wiley-Blackwell, 2010. http://dx.doi.org/10.1002/9781444315806.ch14.
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6
Corrigan, John. "Cosmology." In Religion in American History, 29–48. Oxford, UK: Wiley-Blackwell, 2010. http://dx.doi.org/10.1002/9781444315806.ch2.
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7
Marini, Stephen A. "Cosmology." In Religion in American History, 109–33. Oxford, UK: Wiley-Blackwell, 2010. http://dx.doi.org/10.1002/9781444315806.ch6.
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Mould, Richard A. "Cosmology." In Basic Relativity, 392–424. New York, NY: Springer New York, 1994. http://dx.doi.org/10.1007/978-1-4612-4326-7_14.
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Karttunen, Hannu, Pekka Kröger, Heikki Oja, Markku Poutanen, and Karl Johan Donner. "Cosmology." In Fundamental Astronomy, 429–53. Berlin, Heidelberg: Springer Berlin Heidelberg, 1994. http://dx.doi.org/10.1007/978-3-662-11794-1_20.
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10
Steinhart, Eric. "Cosmology." In Believing in Dawkins, 157–88. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-43052-8_5.
Testo completoAtti di convegni sul tema "Cosmology"
1
Ureña-López, L. Arturo, Miguel Garcia Rocha, Ricardo Lopez Fernandez, Luis F. Rojas Ochoa, and Gabino Torres Vega. "Cosmology." In ADVANCED SUMMER SCHOOL IN PHYSICS 2009: Frontiers in Contemporary Physics. AIP, 2010. http://dx.doi.org/10.1063/1.3507422.
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2
Polchinski, Joseph. "Cosmology." In Proceedings of the 23rd Solvay Conference on Physics. WORLD SCIENTIFIC, 2007. http://dx.doi.org/10.1142/9789812706768_0006.
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3
Belanger, Genevieve. "Cosmology." In Third Linear Collider Physics School 2009. Trieste, Italy: Sissa Medialab, 2011. http://dx.doi.org/10.22323/1.094.0011.
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4
Freedman, D. Z. "Matrix Cosmology." In THE NEW COSMOLOGY: Conference on Strings and Cosmology; The Mitchell Symposium on Observational Cosmology. AIP, 2004. http://dx.doi.org/10.1063/1.1848334.
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5
Kinney, William H. "Inflationary Cosmology." In Proceedings of the 2008 Theoretical Advanced Study Institute in Elementary Particle Physics. WORLD SCIENTIFIC, 2010. http://dx.doi.org/10.1142/9789812838360_0013.
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Shaposhnikov, Mikhail. "Cosmology: theory." In The European Physical Society Conference on High Energy Physics. Trieste, Italy: Sissa Medialab, 2014. http://dx.doi.org/10.22323/1.180.0155.
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Baumann, Daniel. "Primordial Cosmology." In Theoretical Advanced Study Institute Summer School 2017 "Physics at the Fundamental Frontier". Trieste, Italy: Sissa Medialab, 2018. http://dx.doi.org/10.22323/1.305.0009.
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Linde, Andrei. "Inflationary Cosmology." In Proceedings of Nobel Symposium 109. WORLD SCIENTIFIC, 2001. http://dx.doi.org/10.1142/9789812810434_0021.
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Lesgourgues, Julien. "Neutrino cosmology." In International Workshop on Astroparticle and High Energy Physics. Trieste, Italy: Sissa Medialab, 2003. http://dx.doi.org/10.22323/1.010.0052.
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ZAGERMANN, Marco. "String Cosmology." In European Physical Society Europhysics Conference on High Energy Physics. Trieste, Italy: Sissa Medialab, 2010. http://dx.doi.org/10.22323/1.084.0389.
Testo completoRapporti di organizzazioni sul tema "Cosmology"
1
Weinstein, Marvin, and Ratin Akhoury. Quantized Cosmology. Office of Scientific and Technical Information (OSTI), December 2003. http://dx.doi.org/10.2172/826545.
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2
Li, Hui. Astrophysics/Cosmology Status Report. Office of Scientific and Technical Information (OSTI), August 2017. http://dx.doi.org/10.2172/1375895.
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Shafi, Qaisar, Steven Barr, Thomas Gaisser, and Todor Stanev. Particle Theory & Cosmology. Office of Scientific and Technical Information (OSTI), March 2015. http://dx.doi.org/10.2172/1213669.
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Shafi, Qaisar. Particle Theory and Cosmology. Office of Scientific and Technical Information (OSTI), April 2024. http://dx.doi.org/10.2172/2340092.
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Assamagan, Ketevi, Chien-Yi Chen, John Paul Chou, David Curtin, Michael A. Fedderke, Yuri Gershtein, Xiao-Gang He, et al. The Higgs Portal and Cosmology. Office of Scientific and Technical Information (OSTI), April 2016. http://dx.doi.org/10.2172/1255142.
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Jin, Sian, Andre Grosset, and Jesus Pulido. Insitu Compression for Cosmology Simulations. Office of Scientific and Technical Information (OSTI), August 2020. http://dx.doi.org/10.2172/1648072.
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Weinstein, M. Cosmology Quantized in Cosmic Time. Office of Scientific and Technical Information (OSTI), June 2004. http://dx.doi.org/10.2172/826997.
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Weinstein, M. Quantized Cosmology: A Simple Approach. Office of Scientific and Technical Information (OSTI), June 2004. http://dx.doi.org/10.2172/826998.
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Silk, J. I. High energy physics and cosmology. Office of Scientific and Technical Information (OSTI), January 1991. http://dx.doi.org/10.2172/6284286.
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Sehgal, N. The Atacama Cosmology Telescope: Cosmology from Galaxy Clusters Detected via the Sunyaev-Zel'dovich Effect. Office of Scientific and Technical Information (OSTI), August 2011. http://dx.doi.org/10.2172/1022513.
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