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Particle horizon
About: Particle horizon is a research topic. Over the lifetime, 2096 publications have been published within this topic receiving 69137 citations.
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TL;DR: In this article, a study of matter-radiation universes under certain supplementary conditions specified in the introduction shows that the only model of this class compatible with observations is a parabolic universe which at the present time is almost the same as an Einstein-de Sitter model.
Abstract: A study of matter-radiation universes under certain supplementary conditions specified in the introduction shows us that the only model of this class compatible with observations is a parabolic universe which at the present time is almost the same as an Einstein-de Sitter model. The numerical values obtained for Hubble's constant, the age of the universe and the matter density at the present time are quite acceptable. We can also obtain some limits for the mass of neutrinos. The advantage of this parabolic model is that it gives the same results as thet
2/3 model at the present time and what is more could be used in studying problems of the formation of galaxies, after the recombination epoch, where matter and radiation have comparable importance.
2 citations
2 citations
TL;DR: In this paper, the authors constrain the thermal evolution of the universe with a decaying cosmological term by using the method of the analysis for the Wilkinson Microwave Anisotropy Probe (WMAP) observation data.
Abstract: We constrain the thermal evolution of the universe with a decaying cosmological term by using the method of the analysis for the Wilkinson Microwave Anisotropy Probe (WMAP) observation data The cosmological term is assumed to be a function of the scale factor that increases toward the early universe, and the radiation energy density is lower compared to that in the model with the standard cosmological constant ($\ensuremath{\Lambda}\mathrm{CDM}$) The decrease in the radiation density affects the thermal history of the universe; eg the photon decoupling occurs at higher-$z$ compared to the case of the standard $\ensuremath{\Lambda}\mathrm{CDM}$ model As a consequence, a decaying cosmological term affects the cosmic microwave background (CMB) anisotropy Thanks to the Markov-Chain Monte Carlo method, we compare the angular power spectrum in the decaying $\ensuremath{\Lambda}\mathrm{CDM}$ model with the CMB data, and we get severe constraints on parameters of the model
2 citations
TL;DR: In this article, the formation of the first cosmological objects is discussed and state-of-the-art numerical simulations are presented for the first generation of stars and galaxies.
Abstract: The standard theory of cosmic structure formation posits that the present-day rich structure of the Universe developed through gravitational amplification of tiny matter density fluctuations generated in its very early history. Recent observations of the cosmic microwave background, large-scale structure, and distant supernovae determined the energy content of the Universe and the basic statistics of the initial density field with great accuracy. It has become possible to make accurate predictions for the formation and nonlinear growth of structure from early to the present epochs. We review recent progress in the theory of structure formation in the universe. We focus on the formation of the first cosmological objects. Results from state-of-the-art numerical simulations are presented. Finally, we discuss prospects for future observations of the first generation of stars and galaxies.
2 citations