Bulletin of the American Physical Society
APS April Meeting 2013
Volume 58, Number 4
Saturday–Tuesday, April 13–16, 2013; Denver, Colorado
Session Q14: Dark Matter Theory |
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Sponsoring Units: DAP Chair: Jason Kumar, University of Hawaii Room: Plaza Court 3 |
Monday, April 15, 2013 10:45AM - 10:57AM |
Q14.00001: Dark matter annihilation cross section constraints from a joint analysis of Milky Way dwarf galaxies Savvas Koushiappas I will present new results from a joint search for continuum and line emission from dark matter annihilation in Milky Way dwarf galaxies. This analysis is based on a statistically optimal weighting of photons with the inclusion of spatial and spectral information. The results probe generic dark matter WIMP models, and derive the strongest limits to the annihilation cross section of dark matter. [Preview Abstract] |
Monday, April 15, 2013 10:57AM - 11:09AM |
Q14.00002: Neutron star constraints on asymmetric bosonic dark matter Mary Hall Reno, Tolga Guver, Ina Sarcevic, Arif E. Erkoca Given observations of old neutron stars, neutron stars can be used to constrain models of particle dark matter. We evaluate the rate of capture of asymmetric bosonic dark matter by a typical neutron star including interactions of dark matter with both neutrons and with accumulated dark matter. Asymmetric dark matter does not permit dark matter annihilations. We consider the case where dark matter thermalization in the neutron star is slow. The parameter space of dark matter mass, the dark matter cross section with neutrons and the dark matter self-interaction cross section is constrained. [Preview Abstract] |
Monday, April 15, 2013 11:09AM - 11:21AM |
Q14.00003: Dark matter distributions around massive black holes: A fully general relativistic approach Francesc Ferrer, Laleh Sadeghian, Clifford Will The cold dark matter at the center of a galaxy will be redistributed by the presence of a massive black hole. The redistribution may be determined by beginning with a model distribution function for the dark matter, and ``growing'' the black hole adiabatically, holding the adiabatic invariants of the motion constant. Unlike previous approaches, which adopted Newtonian theory together with ad hoc correction factors to mimic general relativistic effects, we carry out the calculation fully relativistically, using the exact Schwarzschild geometry of the black hole. We consider a range of initial distribution functions, including ``cuspy'' profiles, and find that the density spike very close to the black hole is significantly higher than that found previously by Newtonian analyses. The potential implications for detection of signals from galactic center dark matter will be discussed. [Preview Abstract] |
Monday, April 15, 2013 11:21AM - 11:33AM |
Q14.00004: The impact of the phase-space density on the detection of dark matter Daniel Hunter, Francesc Ferrer Fluxes from dark matter annihilation depend on the square of the density, but they also depend on the velocity distribution. For many halo models this cannot be found analytically, and a Maxwell-Boltzmann distribution is often used for the particle velocity in lieu of the correct distribution. However, this is correct only for an isothermal sphere. Furthermore, the shape of the velocity distribution changes throughout the halo. We numerically compute the correct velocity distribution for several halo models and compare luminosity predictions with those found using a Maxwell-Boltzmann distribution. In many cases, the Maxwell-Boltzmann distribution is reasonable, but in others, especially when observing the galactic center, it significantly underestimates the luminosity, implying that the true constraints on dark matter models may be more strict than previously thought. [Preview Abstract] |
Monday, April 15, 2013 11:33AM - 11:45AM |
Q14.00005: The Light Side of Dark Matter Sophia Cisneros We present a new, heuristic, two-parameter model for predicting the rotation curves of disc galaxies. The model is tested on (22) randomly chosen galaxies, represented in 35 data sets. This Lorentz Convolution [LC] model is derived from a non-linear, relativistic solution of a Kerr-type wave equation, where small changes in the photon's frequencies, resulting from the curved space time, are convolved into a sequence of Lorentz transformations. The LC model is parametrized with only the diffuse, \emph{luminous} stellar and gaseous masses reported with each data set of observations used. The LC model predicts observed rotation curves across a wide range of disk galaxies. The LC model was constructed to occupy the same place in the explanation of rotation curves that Dark Matter does, so that a simple investigation of the relation between luminous and dark matter might be made, via by a parameter $(a)$. We find the parameter $(a)$ to demonstrate interesting structure. We compare the new model prediction to both the NFW model and MOND fits when available. [Preview Abstract] |
Monday, April 15, 2013 11:45AM - 11:57AM |
Q14.00006: Theory of Interactions of Non-Relativistic Flavor-Mixed Particles and its possible Implications to the Physics of Dark Matter and the Cosmic Neutrino Background A. Ford, M.V. Medvedev Neutrinos and some dark matter candidates are mixed particles. Here we explore scattering of a non-relativistic stable particle with flavor mixing off of a weak potential. We demonstrate that, in addition to known phenomena such as flavor oscillations, conversions from one mass state to another are possible through elastic scattering and calculate the associated differential cross sections. Finally, we discuss implications of mass conversion to cosmology with flavor-mixed dark matter and to the cosmic neutrino background. [Preview Abstract] |
Monday, April 15, 2013 11:57AM - 12:09PM |
Q14.00007: Thermalization of Axions and Axion like Particles Nilanjan Banik, Pierre Sikivie Cold dark matter candidate axions form a degenerate Bose gas with large correlation length. As a result they thermalize via gravitational self interactions and form a Bose-Einstein condensate (BEC). I will show that thermalization by gravitational self interactions and the subsequent formation of BEC occurs not only for axions but for a broad class of bosons which are created by the vacumm re-alignment mechanism. Thus, besides axions, axion like particles forming a BEC also acquire net overall rotation and form caustic rings in galactic halos. [Preview Abstract] |
Monday, April 15, 2013 12:09PM - 12:21PM |
Q14.00008: Mirage Models Confront the LHC: K\"ahler-Stabilized Heterotic String Theory Bryan Kaufman, Brent Nelson We begin the study of a class of string-motivated effective supergravity theories in light of current data from the CERN Large Hadron Collider (LHC). In particular, the case of heterotic string theory in which the dilaton is stabilized via non-perturbative corrections to the K\"ahler metric will be discussed. This model is highly constrained and therefore predictive. We find that most of the reasonable parameter space afforded to the model -- representing the strong dynamics of a presumed gaugino condensation in the hidden sector -- is now observationally disfavored by the LHC results. What limited parameter space that remains will be definitively explored within the first year of operation at $\sqrt{s} = 13\,{\rm TeV}$, and much will be explored even before data-taking ends in~2013. Expected signatures for a number of benchmark points are discussed. This represents the first example of an explicit string-based model with the potential to be falsified by observational data. We find that the surviving space of the model makes a precise prediction as to the relation of many superpartner masses, as well as the manner in which the correct dark matter relic density is obtained. Implications for current and future dark matter search experiments are discussed. [Preview Abstract] |
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