69 research outputs found
Generation of gravitational waves during early structure formation between cosmic inflation and reheating
In the pre-reheating era, following cosmic inflation and preceding radiation
domination, the energy density may be dominated by an oscillating massive
scalar condensate, such as is the case for quadratic chaotic inflation. We have
found in a previous paper that during this period, a wide range of sub-Hubble
scale perturbations are subject to a preheating instability, leading to the
growth of density perturbations ultimately collapsing to form non-linear
structures. We compute here the gravitational wave signal due to these
structures in the linear limit and present estimates for emission in the
non-linear limit due to various effects: the collapse of halos, the tidal
interactions, the evaporation during the conversion of the inflaton condensate
into radiation and finally the ensuing turbulent cascades. The gravitational
wave signal could be rather large and potentially testable by future detectors.Comment: 11 pages, 3 figure
Gravitino dark matter with constraints from Higgs boson mass and sneutrino decays
We investigate gravitino dark matter produced thermally at high temperatures
and in decays of a long-lived sneutrino. We consider the Non-Universal Higgs
Model and a generalized gauge mediation model, and in each case identify
sneutrino LOSP regions of the parameter space consistent with the mass of the
Higgs-like boson observed at the LHC. We apply relevant collider and
cosmological bounds, including constraints from Big Bang Nucleosynthesis and
from warm dark matter on large scale structures. Generally, we find allowed
values of the reheating temperature TR below 10^9 GeV, i.e. somewhat smaller
than the values needed for thermal leptogenesis, even with a conservative lower
bound of 122 GeV on the Higgs mass. Requiring mass values closer to 126 GeV
implies TR below 10^7 GeV and the gravitino mass less than 10 GeV.Comment: 19 pages, 19 figures, version published in JHE
B-ball Dark Matter and Baryogenesis
It has been recently suggested that stable, supersymmetric B-balls formed in
the early universe could not only be the dark matter at the present epoch, but
also be responsible for baryogenesis by their partial evaporation at high
temperatures. We reinvestigate the efficiency of B-ball baryogenesis and find
it to be limited by the diffusion of baryon number away from the B-balls.
Successful baryogenesis may only occur for B-balls with charges Q\simle 10^{20}
- 5\times 10^{23}, which is close to the observational lower limits on the Q of
a significant B-ball dark matter component. We also present some cosmological
constraints on the abundances of larger B-balls in the early universe.Comment: published version, minor changes and reference adde
Cosmological Deuterium Production in Non-Standard Scenarios
It is widely believed that the cosmic baryon density may be obtained by
inferring deuterium abundances in low-metallicity quasar absorption line
systems. The implicit assumptions which enter this argument are critically
assessed. In particular, the production of deuterium in non-standard Big Bang
nucleosynthesis scenarios, the putative production of deuterium in
astrophysical environments, and the possible destruction of deuterium via
non-standard chemical evolution are discussed.Comment: 11 pages, article based on a talk presented at "Deuterium in the
Universe", Meudon, June 2001, to be published in Planetary and Space Scienc
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