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Title: Big bang nucleosynthesis constraints on universal extra dimensions and varying fundamental constants

Abstract

The successful prediction of light element abundances from big bang nucleosynthesis (BBN) has been a pillar of the standard model of cosmology. Because many of the relevant reaction rates are sensitive to the values of fundamental constants, such as the fine structure constant and the strong coupling constant, BBN is a useful tool to probe and to put constraints on possible cosmological variations of these constants, which arise naturally from many versions of extra-dimensional theories. In this paper, we study the dependences of fundamental constants on the radion field of the universal extra-dimension model, and calculate the effects of such varying constants on BBN. We also discuss the possibility that the discrepancy between BBN and the Wilkinson Microwave Anisotropy Probe (WMAP) data on the baryon-to-photon ratio can be reduced if the volume of the extra dimensions was slightly larger--by O(10{sup -3})--at the BBN era compared to its present value, which would result in smaller gauge couplings at BBN by the same factor.

Authors:
;  [1]
  1. Department of Physics, Chinese University of Hong Kong, Hong Kong (China)
Publication Date:
OSTI Identifier:
20795748
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. D, Particles Fields; Journal Volume: 73; Journal Issue: 2; Other Information: DOI: 10.1103/PhysRevD.73.025004; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ANISOTROPY; BARYONS; COSMOLOGY; ELEMENT ABUNDANCE; FINE STRUCTURE; FUNDAMENTAL CONSTANTS; NUCLEAR REACTION KINETICS; NUCLEOSYNTHESIS; PHOTONS; RELICT RADIATION; STANDARD MODEL; STRONG-COUPLING MODEL; VARIATIONS

Citation Formats

Li, B., and Chu, M.-C. Big bang nucleosynthesis constraints on universal extra dimensions and varying fundamental constants. United States: N. p., 2006. Web. doi:10.1103/PHYSREVD.73.0.
Li, B., & Chu, M.-C. Big bang nucleosynthesis constraints on universal extra dimensions and varying fundamental constants. United States. doi:10.1103/PHYSREVD.73.0.
Li, B., and Chu, M.-C. Sun . "Big bang nucleosynthesis constraints on universal extra dimensions and varying fundamental constants". United States. doi:10.1103/PHYSREVD.73.0.
@article{osti_20795748,
title = {Big bang nucleosynthesis constraints on universal extra dimensions and varying fundamental constants},
author = {Li, B. and Chu, M.-C.},
abstractNote = {The successful prediction of light element abundances from big bang nucleosynthesis (BBN) has been a pillar of the standard model of cosmology. Because many of the relevant reaction rates are sensitive to the values of fundamental constants, such as the fine structure constant and the strong coupling constant, BBN is a useful tool to probe and to put constraints on possible cosmological variations of these constants, which arise naturally from many versions of extra-dimensional theories. In this paper, we study the dependences of fundamental constants on the radion field of the universal extra-dimension model, and calculate the effects of such varying constants on BBN. We also discuss the possibility that the discrepancy between BBN and the Wilkinson Microwave Anisotropy Probe (WMAP) data on the baryon-to-photon ratio can be reduced if the volume of the extra dimensions was slightly larger--by O(10{sup -3})--at the BBN era compared to its present value, which would result in smaller gauge couplings at BBN by the same factor.},
doi = {10.1103/PHYSREVD.73.0},
journal = {Physical Review. D, Particles Fields},
number = 2,
volume = 73,
place = {United States},
year = {Sun Jan 15 00:00:00 EST 2006},
month = {Sun Jan 15 00:00:00 EST 2006}
}
  • We analyze the effect of variation of fundamental couplings and mass scales on primordial nucleosynthesis in a systematic way. The first step establishes the response of primordial element abundances to the variation of a large number of nuclear physics parameters, including nuclear binding energies. We find a strong influence of the n-p mass difference, of the nucleon mass and of A = 3,4,7 binding energies. A second step relates the nuclear parameters to the parameters of the Standard Model of particle physics. The deuterium, and, above all, 7Li abundances depend strongly on the average light quark mass. We calculate themore » behaviour of abundances when variations of fundamental parameters obey relations arising from grand unification. We also discuss the possibility of a substantial shift in the lithium abundance while the deuterium and 4He abundances are only weakly affected.« less
  • We investigate the big-bang nucleosynthesis (BBN) in a Brans-Dicke model with a varying {lambda} term. We find that the cosmic expansion rate differs appreciably from that of the Friedmann model during the BBN epoch . The produced abundances of 4He, D, and 7Li are consistent with both the observed ones and the baryon density obtained from WMAP.
  • It is pointed out that the constraints on the mean radius of the extra dimensions at the time of primordial nucleosynthesis obtained by Kolb, Perry, and Walker get modified if primordial neutrinos are degenerate. Similarly, the constraints on the neutrino degeneracy parameters obtained from primordial nucleosynthesis also change if the volume of the extra dimensions at the time of nucleosynthesis is different than its present value.
  • In theories with extra dimensions, the dependence of fundamental constants on the volume of the compact space allows one to use primordial nucleosynthesis to probe the structure of compact dimensions during the first few minutes after the big bang. Requiring the yield of primordial sup4He to be within acceptable limits, we find that in ten-dimensional superstring models the size of the extra dimensions during primordial nucleosynthesis must have been within 0.5% of their current value, while in Kaluza-Klein models the extra dimensions must have been within 1% of their current value.
  • In the early Universe, the relative abundance of a massive weakly interacting particle species freezes out'' when the annihilation rate becomes less than the expansion rate. Although ineffective in reducing the total number of the species, occasional annihilations still occur after freeze-out. The residual annihilations of massive particles (10 MeV{approx lt}{ital m}{sub {ital X}}{approx lt}1 GeV) after primordial nucleosynthesis can strongly alter the light-element abundances through photodissociation. For particles with typical weak-interaction cross sections and lifetimes {tau}{sub {ital X}}{approx gt}5{times}10{sup 6} sec, we find that the mass range {ital m}{sub {ital X}}{approx lt}1 GeV is ruled out, independent of howmore » they subsequently decay.« less