920 research outputs found
Particle decays during the cosmic dark ages
We consider particle decays during the cosmic dark ages with two aims: (1) to explain the high optical depth reported by the Wilkinson Microwave Anisotropy Probe (WMAP), and (2) to provide new constraints to the parameter space for decaying particles. We delineate the decay channels in which most of the decay energy ionizes and heats the intergalactic medium gas [and thus affects the cosmic microwave background (CMB)], and those in which most of the energy is carried away—e.g. photons with energies 100 keV<~E<~1 TeV—and thus appears as a contribution to diffuse x-ray and gamma-ray backgrounds. The new constraints to the decay-particle parameters from the CMB power spectrum thus complement those from the cosmic x-ray and gamma-ray backgrounds. Although decaying particles can indeed produce an optical depth consistent with that reported by WMAP, in so doing they produce new fluctuations in the CMB temperature and polarization power spectra. For decay lifetimes less than the age of the Universe, the induced power spectra generally violate current constraints, while the power spectra are usually consistent if the lifetime is longer than the age of the Universe
Relic Abundance of Asymmetric Dark Matter in Quintessence
We investigate the relic abundance of asymmetric Dark Matter particles in
quintessence model with a kination phase. The analytic calculation of the
asymmetric Dark Matter in the standard cosmological scenario is extended to the
nonstandard cosmological scenario where we specifically discuss the
quintessence model with a kination phase. We found that the enhancement of
Hubble rate changes the relic density of particles and anti--particles. We use
the present day Dark Matter abundance to constrain the Hubble rate in
quintessence model with a kination phase for asymmetric Dark Matter.Comment: 13 pages, 9 figure
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