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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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Journal ArticleDOI
TL;DR: In this paper, the authors study the space-time evolution of the fine structure constant, α, inside evolving spherical overdensities in a lambda-CDM Friedmann universe using the spherical infall model.

225 citations

Journal ArticleDOI
TL;DR: In this paper, the trispectrum of the primordial curvature perturbation generated by an epoch of slow-roll inion in the early universe has been calculated, and it is shown that the non-Gaussian signature imprinted at horizon crossing is unobservably small, of order lambda NL less than or similar to r/50.
Abstract: We calculate the trispectrum of the primordial curvature perturbation generated by an epoch of slow-roll in. ation in the early universe, and demonstrate that the non-Gaussian signature imprinted at horizon crossing is unobservably small, of order lambda NL less than or similar to r/50, where r < 1 is the tensor-to-scalar ratio. Therefore any primordial non-Gaussianity observed in future microwave background experiments is likely to have been synthesized by gravitational effects on superhorizon scales. We discuss the application of Maldacena's consistency condition to the trispectrum.

221 citations

Journal ArticleDOI
TL;DR: In this paper, a review of recent results concerning the global structure of the inflationary universe, which have been obtained within stochastic approach to inflation, is given, and it is shown in particular that the evolution of the universe in the chaotic inflation scenario has no end and may have no beginning.
Abstract: In this article we give a review of recent results concerning the global structure of the inflationary universe, which have been obtained within stochastic approach to inflation. It is shown in particular that the evolution of the universe in the chaotic inflation scenario has no end and may have no beginning. In this scenario the major part of the physical volume of the universe always remains in the inflationary phase. During inflation the universe becomes divided into many exponentially large domains, inside which all possible metastable vacuum states and all possible types of compactification compatible with inflation are realized.

220 citations

Journal ArticleDOI
30 Oct 1948-Nature
TL;DR: It is concluded first of all that the relative abundances of various atomic species must represent the most ancient archæological document pertaining to the history of the universe, and that it must have been established during the earliest stages of expansion.
Abstract: THE discovery of the red shift in the spectra of distant stellar galaxies revealed the important fact that our universe is in the state of uniform expansion, and raised an interesting question as to whether the present features of the universe could be understood as the result of its evolutionary development, which must have started a few thousand million years ago from a homogeneous state of extremely high density and temperature. We conclude first of all that the relative abundances of various atomic species (which were found to be essentially the same all over the observed region of the universe) must represent the most ancient archaeological document pertaining to the history of the universe. These abundances must have been established during the earliest stages of expansion when the temperature of the primordial matter was still sufficiently high to permit nuclear transformations to run through the entire range of chemical elements. It is also interesting to notice that the observed relative amounts of natural radioactive elements suggest that their nuclei must have been formed (presumably along with all other stable nuclei) rather soon after the beginning of the universal expansion. In fact, we notice that natural radioactive isotopes with the decay periods of many thousand million years (such as uranium-238, thorium-232 and samarium-148) are comparatively abundant, whereas those with decay periods measuring only several hundred million years are extremely rare (as uranium-235 and potassium-40). If, using the known decay periods and natural abundances of these isotopes, we try to calculate the date when they have been about as abundant as the corresponding isotopes of longer life, we find that it must have been a few thousand million years ago, in general agreement with the astronomically determined age of the universe.

219 citations

Journal ArticleDOI
TL;DR: In this paper, the authors study the uniqueness and robustness of acoustic signatures in the cosmic microwave background by allowing for the possibility that they are generated by some as yet unknown source of gravitational perturbations.
Abstract: We study the uniqueness and robustness of acoustic signatures in the cosmic microwave background by allowing for the possibility that they are generated by some as yet unknown source of gravitational perturbations. The acoustic pattern of peak locations and relative heights predicted by the standard inflationary cold dark matter model is essentially unique, and its confirrmation would have deep implications for the causal structure of the early universe. A generic pattern for isocurvature initial conditions arises due to backreaction effects but is not robust to exotic source behavior inside the horizon. If present, the acoustic pattern contains unambiguous information on the curvature of the universe even in the general case. By classifying the behavior of the unknown source, we determine the minimal observations necessary for robust constraints on the curvature. The diffusion damping scale provides an entirely model-independent cornerstone upon which to build such a measurement. The peak spacing, if regular, supplies a precision test.

215 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202320
202247
20216
202010
201910
201814