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How Asymmetric Dark Matter May Alter the Conditions of Stardom – Andrew Zentner

Date: Tue. September 27th, 2011, 11:30 am-12:30 pm
Location: Rockefeller 221

Numerous recent experimental results have reinforced interest in a class of models dubbed “Asymmetric Dark Matter” (ADM), in which the relic dark matter density results from a particle-antiparticle asymmetry. Early models of this sort were invoked to explain the fact that the cosmic baryon and dark matter densities are of the same order, yet in the standard cosmology, they are produced by distinct physical processes. In such models, the relic dark matter density results from an asymmetry (perhaps dark matter carries B-L charge), so there are no contemporary cosmic dark matter annihilations and no opportunity for indirect detection. Otherwise, these scenarios give essentially the same cosmological predictions as the standard weakly-interacting massive particle/cold dark matter paradigm, except that ADM has a relatively low mass, ~5–30 GeV. I will discuss stellar evolution in such scenarios. In particular, I will show that ADM captured by low-mass stars (M less than 0.1 Msun) can cool the cores of these stars. In some cases, this cooling can make it impossible for main sequence hydrogen burning to begin, determining in part whether or not these objects become stars at all! More generally, for interesting regions of parameter space, such as those relevant to the DAMA, CoGeNT, and CRESST-II preliminary positive direct detection signals, ADM will lead to dimmer low-mass stars than and brown dwarfs that cool much more rapidly than otherwise expected. These results are timely because ADM is otherwise not amenable to indirect detection and numerous forthcoming astronomical observatories such as the LSST, Pan-STARRS, JWST, TMT, and GMT count the demographics of nearby and distant low-mass star and brown dwarfs as among their primary science drivers.

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