Big-bang nucleosynthesis as a probe of cosmology and particle physics

1981 ◽  
Vol 246 ◽  
pp. 557 ◽  
Author(s):  
K. A. Olive ◽  
D. N. Schramm ◽  
M. S. Turner ◽  
J. Yang ◽  
G. Steigman
Keyword(s):  
Particle Physics ◽  
Big Bang ◽  
Big Bang Nucleosynthesis

scholarly journals Neutrinos and Big Bang Nucleosynthesis

2012 ◽  
Vol 2012 ◽  
pp. 1-24 ◽  
Author(s):  
Gary Steigman
Keyword(s):  
Particle Physics ◽  
Weak Interactions ◽  
Big Bang ◽  
Baryon Density ◽  
Big Bang Nucleosynthesis ◽  
Lepton Asymmetry ◽  
Lithium Abundance ◽  
Dark Radiation ◽  
Cosmic Neutrino Background ◽  
Neutrino Background

According to the standard models of particle physics and cosmology, there should be a background of cosmic neutrinos in the present Universe, similar to the cosmic microwave photon background. The weakness of the weak interactions renders this neutrino background undetectable with current technology. The cosmic neutrino background can, however, be probed indirectly through its cosmological effects on big bang nucleosynthesis (BBN) and the cosmic microwave background (CMB) radiation. In this BBN review, focused on neutrinos and more generally on dark radiation, the BBN constraints on the number of “equivalent neutrinos” (dark radiation), on the baryon asymmetry (baryon density), and on a possible lepton asymmetry (neutrino degeneracy) are reviewed and updated. The BBN constraints on dark radiation and on the baryon density following from considerations of the primordial abundances of deuterium and helium-4 are in excellent agreement with the complementary results from the CMB, providing a suggestive, but currently inconclusive, hint of the presence of dark radiation, and they constrain any lepton asymmetry. For all the cases considered here there is a “lithium problem”: the BBN-predicted lithium abundance exceeds the observationally inferred primordial value by a factor of~3.

Catalyzed Big-Bang nucleosynthesis

2008 ◽  
Vol 86 (4) ◽  
pp. 611-616
Author(s):  
M Pospelov
Keyword(s):  
Particle Physics ◽  
Bound States ◽  
Charged Particles ◽  
Big Bang ◽  
Number Density ◽  
Electroweak Scale ◽  
Big Bang Nucleosynthesis ◽  
Elemental Abundances ◽  
Subsequent Decay ◽  
Standard Channel

We point out that the existence of metastable, τ >103 s, negatively charged electroweak-scale particles (X–) alters the predictions for lithium and other primordial elemental abundances for A > 4 via the formation of bound states with nuclei during Big-Bang nucleosynthesis (BBN). In particular, we show that the bound states of X– with helium, formed at temperatures of about T = 108 K, lead to the catalytic enhancement of 6Li production, which is eight orders of magnitude more efficient than the standard channel. In particle physics models, where subsequent decay of X– does not lead to large nonthermal BBN effects, this directly translates to the level of sensitivity to the number density of long-lived X– particles (τ > 105 s) relative to entropy of nX – / s [Formula: see text] 3 × 10–17, which is one of the most stringent probes of electroweak scale remnants known to date. It is also argued that unstable charged particles with lifetime of order ~2000 s may naturally lead to the depletion of 7Li by a factor of two, making it consistent with observationally determined abundances. PACS No.: 98.80.Ft

scholarly journals Nonperturbative dynamics of reheating after inflation: A review

2014 ◽  
Vol 24 (01) ◽  
pp. 1530003 ◽  
Author(s):  
Mustafa A. Amin ◽  
Mark P. Hertzberg ◽  
David I. Kaiser ◽  
Johanna Karouby
Keyword(s):  
Particle Physics ◽  
High Energy Physics ◽  
Thermal State ◽  
High Energy ◽  
Big Bang ◽  
Big Bang Nucleosynthesis ◽  
Potential Source ◽  
Numerical Tools ◽  
The Universe ◽  
Energy Physics

Our understanding of the state of the universe between the end of inflation and big bang nucleosynthesis (BBN) is incomplete. The dynamics at the end of inflation are rich and a potential source of observational signatures. Reheating, the energy transfer between the inflaton and Standard Model fields (possibly through intermediaries) and their subsequent thermalization, can provide clues to how inflation fits in with known high-energy physics. We provide an overview of our current understanding of the nonperturbative, nonlinear dynamics at the end of inflation, some salient features of realistic particle physics models of reheating, and how the universe reaches a thermal state before BBN. In addition, we review the analytical and numerical tools available in the literature to study preheating and reheating and discuss potential observational signatures from this fascinating era.

Helium in Three H II Galaxies and the Helium Abundance

1990 ◽  
Vol 8 (3) ◽  
pp. 243-245
Author(s):  
B. E. J. Pagel ◽  
E. A. Simonson
Keyword(s):  
Particle Physics ◽  
Hubble Constant ◽  
Big Bang ◽  
Density Fluctuations ◽  
Microwave Background ◽  
Big Bang Nucleosynthesis ◽  
Hadron Phase ◽  
The Mean ◽  
The Big Bang ◽  
The Universe

Extended abstractThe mass-fraction Y of helium in the interstellar medium is between 0.22 and 0.30 wherever it has been measured and it is believed to be the sum of two components: YP from Big Bang nucleosynthesis (BBNS) at about 100 s after the Big Bang (ABB) and a temperature near 0.1 MeV, and ΔY due to processing in stars. Precise measurements of Yp, along with balances of trace elements D, 3He, 7Li also resulting from BBNS, provide important tests of BBNS theory and of parameters of cosmology and particle physics, notably the contribution ΩBO of baryons to the mean density of matter in the universe (in units of the closure density), the number Nv of light neutrino flavours (or families of quarks and leptons) and the half-life т½ of the neutron (Shaver et al. 1983; Yang et al. 1984; Boesgaard and Steigman 1985). Figure 1 shows the predicted abundances from Standard BBNS theory (SBBN) as a function of η = μB/nλ the ratio of baryons to photons (unchanged since e± annihilation a few seconds ABB), which is proportional (through the known temperature of the microwave background) to ΩBOh20 where h0 is the Hubble constant in units of 100 km s−1 Mpc−1. SBBN theory (which assumes a homogeneous Friedmann universe and small lepton numbers), when combined with reasonable ideas on Galactic chemical evolution that predict a primordial (D + 3He)/H ratio below 10−4, imply that η ≥ 3 × 10−10 (shown by the tall vertical line in Fig. 1), which in turn implies YP≥0.210 if Nv = 3 and т½≥10.4 minutes. But this limit can be somewhat relaxed if т½ is smaller (current measurements permit values down to 9.0 minutes, e.g. Last et al. 1988) and/or if the quark-hadron phase transition around 200 MeV is first-order and leads to significant density fluctuations (Kurki-Sunonio et al. 1989; Reeves 1989).

The Cosmic Mystery Tour

2019 ◽  
Author(s):  
Nicholas Mee
Keyword(s):  
Science Fiction ◽  
Particle Physics ◽  
Cultural Context ◽  
Big Bang ◽  
Galactic Centre ◽  
Red Giants ◽  
Extraterrestrial Life ◽  
Modern Physics ◽  
Recent Developments ◽  
The Universe

The Cosmic Mystery Tour is a brief account of modern physics and astronomy presented in a broad historical and cultural context. The book is attractively illustrated and aimed at the general reader. Part I explores the laws of physics including general relativity, the structure of matter, quantum mechanics and the Standard Model of particle physics. It discusses recent discoveries such as gravitational waves and the project to construct LISA, a space-based gravitational wave detector, as well as unresolved issues such as the nature of dark matter. Part II begins by considering cosmology, the study of the universe as a whole and how we arrived at the theory of the Big Bang and the expanding universe. It looks at the remarkable objects within the universe such as red giants, white dwarfs, neutron stars and black holes, and considers the expected discoveries from new telescopes such as the Extremely Large Telescope in Chile, and the Event Horizon Telescope, currently aiming to image the supermassive black hole at the galactic centre. Part III considers the possibility of finding extraterrestrial life, from the speculations of science fiction authors to the ongoing search for alien civilizations known as SETI. Recent developments are discussed: space probes to the satellites of Jupiter and Saturn; the discovery of planets in other star systems; the citizen science project SETI@Home; Breakthrough Starshot, the project to develop technologies to send spacecraft to the stars. It also discusses the Fermi paradox which argues that we might actually be alone in the cosmos

scholarly journals Xenon-1T excess as a possible signal of a sub-GeV hidden sector dark matter

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Amin Aboubrahim ◽  
Michael Klasen ◽  
Pran Nath
Keyword(s):  
Dark Matter ◽  
Particle Physics ◽  
Small Mass ◽  
Big Bang ◽  
Mass Splitting ◽  
Recoil Energy ◽  
Dirac Fermions ◽  
Dark Sector ◽  
Dark Photon ◽  
Physics Model

Abstract We present a particle physics model to explain the observed enhancement in the Xenon-1T data at an electron recoil energy of 2.5 keV. The model is based on a U(1) extension of the Standard Model where the dark sector consists of two essentially mass degenerate Dirac fermions in the sub-GeV region with a small mass splitting interacting with a dark photon. The dark photon is unstable and decays before the big bang nucleosynthesis, which leads to the dark matter constituted of two essentially mass degenerate Dirac fermions. The Xenon-1T excess is computed via the inelastic exothermic scattering of the heavier dark fermion from a bound electron in xenon to the lighter dark fermion producing the observed excess events in the recoil electron energy. The model can be tested with further data from Xenon-1T and in future experiments such as SuperCDMS.

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