Topic
Cosmology
About: Cosmology is a research topic. Over the lifetime, 18004 publications have been published within this topic receiving 631028 citations. The topic is also known as: physical cosmology & cosmologies.
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TL;DR: In this article, it was shown that the presence of a singularity with respect to time is not a necessary property of cosmological models of the general theory of relativity, and that the general case of an arbitrary distribution of matter and gravitational field does not lead to the appearance of singularity.
Abstract: (by translator) A detailed report is given here of the general investigations carried out by the authors in the field of relativistic cosmology during the past years. The paper consists of two parts. The first part is devoted to a study of the singularities of the cosmological solutions of the gravitational equations. An attempt is made to provide an answer to one of the principal questions of modern cosmology: ‘does the general solution of the gravitational equations have a singularity?’ The authors give a negative answer to this question. The study carried out leads, in fact, to the general conclusion that the presence of a singularity with respect to time is not a necessary property of cosmological models of the general theory of relativity, and that the general case of an arbitrary distribution of matter and gravitational field does not lead to the appearance of a singularity. This result, however, does not exclude the possibility of the existence of more restricted classes of cosmological so...
808 citations
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TL;DR: In this article, the authors measure the clustering of dark matter halos in a large set of collisionless cosmological simulations of the flatCDM cosmology, and find that the bias of rare halos is higher than that predicted in the modified ellipsoidal collapse model of Sheth, Mo, & Tormen (2001), and approaches the predictions of the spherical collapse model for the rarest halos.
Abstract: We measure the clustering of dark matter halos in a large set of collisionless cosmological simulations of the flatCDM cosmology. Halos are identified using the spherical over density algorithm, which finds the mass around isolated peaks in the density field such that the m ean density istimes the background. We calibrate fitting functions for the large scale bias that are adaptable to any value ofwe examine. We find a � 6% scatter about our best fit bias relation. Our fitting functi ons couple to the halo mass functions of Tinker et. al. (2008) such that bias of all dark matter is normalized to unity. We demonstrate that the bias of massive, rare halos is higher than that predicted in the modified ellip soidal collapse model of Sheth, Mo, & Tormen (2001), and approaches the predictions of the spherical collapse model for the rarest halos. Halo bias results based on friends-of-friends halos identified with linking l ength 0.2 are systematically lower than for halos with the canonical � = 200 overdensity by � 10%. In contrast to our previous results on the mass function, we find that the universal bias function evolves very weakly with redshift, if at all. We use our numerical results, both for the mass function and the bias relation, to test the peak- background split model for halo bias. We find that the peak-background split achieves a reasonable agreement with the numerical results, but � 20% residuals remain, both at high and low masses. Subject headings:cosmology:theory — methods:numerical — large scale structure of the universe
803 citations
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TL;DR: In this paper, physical motivations, phenomenological consequences, and open problems of the so-called pre-big bang scenario in superstring cosmology are reviewed, as well as some open problems.
803 citations
01 Jan 2003
TL;DR: In this paper, the authors use the Wilkinson Microwave Anisotropy Probe (WMAP) data, in combination with complementary small-scale cosmic microwave background (CMB) measurements and large-scale structure data, to explore the parameter space of inflationary models that is consistent with the WMAP data.
Abstract: We confront predictions of inflationary scenarios with the Wilkinson Microwave Anisotropy Probe (WMAP) data, in combination with complementary small-scale cosmic microwave background (CMB) measurements and large-scale structure data. The WMAP detection of a large-angle anticorrelation in the temperature-polarization cross-power spectrum is the signature of adiabatic superhorizon fluctuations at the time of decoupling. The WMAP data are described by pure adiabatic fluctuations: we place an upper limit on a correlated cold dark matter (CDM) isocurvature component. Using WMAP constraints on the shape of the scalar power spectrum and the amplitude of gravity waves, we explore the parameter space of inflationary models that is consistent with the data. We place limits on inflationary models; for example, a minimally coupled �� 4 is disfavored at more than 3 � using WMAP data in combination with smaller scale CMB and large-scale structure survey data. The limits on the primordial parameters using WMAP data alone are nsðk0 ¼ 0:002 Mpc � 1 Þ¼ 1:20 þ0:12 � 0:11 , dns=d ln k ¼� 0:077 þ0:050 � 0:052 , Aðk0 ¼ 0:002 Mpc � 1 Þ¼ 0:71 þ0:10 � 0:11 (68% CL), and rðk0 ¼ 0:002 Mpc � 1 Þ < 1:28 (95% CL). Subject headings: cosmic microwave background — cosmology: observations — early universe
802 citations