Despite the great successes of the Cold Dark Matter (CDM) model in
explaining a wide range of observations of the global evolution and the formation of galaxies and large-scale structure in the universe, the origin and microscopic nature of this dark matter is still unknown. The most common form of CDM considered to-date is that of Weakly Interacting Massive Particles (WIMPs), but some of the cosmological predictions for this kind of CDM are in apparent conflict with observations (e.g. cuspy-cored halos and an overabundance of satellite dwarf galaxies). For these reasons, it is important to consider the consequences of different forms
of CDM. We focus here on the hypothesis that the dark matter is comprised, instead, of ultralight bosons that form a Bose-Einstein Condensate (BEC),
described by a complex scalar field.
We start from the Klein-Gordon and Einstein field equations to describe
the evolution of the Friedmann-Robertson-Walker (FRW) universe in the presence of this kind of dark matter. We find that, in addition to the
phases of radiation-domination (RD), matter-domination (MD) and
Lambda-domination (LD) familiar from the standard CDM model, there is an
earlier phase of scalar-field-domination (SFD) which is special to this model. In addition, while WIMP CDM is non-relativistic at all times after
it decouples, the equation of state of BEC-SFDM is found to be relativistic at early times, evolving from incompressible ($\bar{p} = \bar{\rho}$)
to radiation-like ($\bar{p} = \bar{\rho}/3$), before it becomes non-relativistic and CDM-like at late times. The timing of the transitions between these
phases and regimes is shown to yield fundamental constraints on the particle
mass and self-interaction coupling strength. We also discuss progress
on the description of structure formation in this model, which includes
additional constraints on these parameters. / text
| Identifer | oai:union.ndltd.org:UTEXAS/oai:repositories.lib.utexas.edu:2152/21308 |
| Date | 24 September 2013 |
| Creators | Li, Bohua |
| Source Sets | University of Texas |
| Language | en_US |
| Detected Language | English |
| Format | application/pdf |
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