Bulk Viscosity, Decaying Dark Matter, and the Cosmic Acceleration

Details Bulk Viscosity, Decaying Dark Matter, and the Cosmic Acceleration Bulk Viscosity, Decaying Dark Matter, and the Cosmic Acceleration

2006-09-25

arxiv.org/abs/astro-ph/0609687v1

Phys.Rev.D75:043521,2007

Astronomy and Astrophysics

Astrophysics

7 pages, 4 figures

Scientific paper

10.1103/PhysRevD.75.043521

We discuss a cosmology in which cold dark-matter particles decay into relativistic particles. We argue that such decays could lead naturally to a bulk viscosity in the cosmic fluid. For decay lifetimes comparable to the present hubble age, this bulk viscosity enters the cosmic energy equation as an effective negative pressure. We investigate whether this negative pressure is of sufficient magnitude to account fo the observed cosmic acceleration. We show that a single decaying species in a flat, dark-matter dominated cosmology without a cosmological constant cannot reproduce the observed magnitude-redshift relation from Type Ia supernovae. However, a delayed bulk viscosity, possibly due to a cascade of decaying particles may be able to account for a significant fraction of the apparent cosmic acceleration. Possible candidate nonrelativistic particles for this scenario include sterile neutrinos or gauge-mediated decaying supersymmetric particles.

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