14,439 research outputs found
Aspects of production and kinetic decoupling of non-thermal dark matter
We reconsider non-thermal production of WIMP dark matter in a systematic way
and using a numerical code for accurate computations of dark matter relic
densities. Candidates with large pair annihilation rates are favored,
suggesting a connection with the anomalies in the lepton cosmic-ray flux
detected by Pamela and Fermi. Focussing on supersymmetric models we will
consider the impact of non-thermal production on the preferred mass scale for
dark matter neutralinos. We have also developed a new formalism to solve the
Boltzmann's equation for a system of coannihilating species without assuming
kinetic equilibrium and applied it to the case of pure Winos.Comment: Proceedings for the conference TAUP 201
Features of deSitter Vacua in M-Theory
We compute the masses of all moduli in the unstable deSitter vacua arising in
the toy model of cosmological M-theory flux compactifications on the G2
holonomy manifolds of [1]. The slow-roll parameters in the tachyonic directions
are shown to be too large to be useful for conventional models of inflation.
However, it appears that we can find fast roll regimes which could, under
certain conditions, account for the current dark energy driven accelerated
expansion of the universe.Comment: 14 pages, 1 figur
Superconformal field theories from crystal lattices
We propose a brane configuration for the (2+1)d,
superconformal theories (CFT) arising from M2-branes probing toric
Calabi-Yau 4-fold cones, using a T-duality transformation of M-theory. We
obtain intersections of M5-branes on a three-torus which form a 3d bipartite
crystal lattice in a way similar to the 2d dimer models for CFT. The
fundamental fields of the CFT are M2-brane discs localized around the
intersections, and the super-potential terms are identified with the atoms of
the crystal. The model correctly reproduces the complete BPS spectrum of mesons
and baryons.Comment: 4 pages, 4 figures, revtex; v2. references added, minor correction
Multi-frequency, Multi-Epoch Study of Mrk 501: Hints for a two-component nature of the emission
Since the detection of very high energy (VHE) -rays from Mrk 501, its
broad band emission of radiation was mostly and quite effectively modeled using
one zone emission scenario. However, broadband spectral and flux variability
studies enabled by the multiwavelength campaigns carried out during the recent
years have revealed rather complex behavior of Mrk 501. The observed emission
from Mrk 501 could be due to a complex superposition of multiple emission
zones. Moreover new evidences of detection of very hard intrinsic -ray
spectra obtained from {\it Fermi}--LAT observations have challenged the
theories about origin of VHE -rays. Our studies based on {\it
Fermi}--LAT data indicate the existence of two separate components in the
spectrum, one for low energy -rays and the other for high energy
-rays. Using multiwaveband data from several ground and space based
instruments, in addition to HAGAR data, the spectral energy distribution of
Mrk~501 is obtained for various flux states observed during 2011. In the
present work, this observed broadband spectral energy distribution is
reproduced with a leptonic, multi-zone Synchrotron Self-Compton model.Comment: Published in Astrophysical Journal (ApJ
Superconductors from Superstrings
We establish that in a large class of strongly coupled 3+1 dimensional N=1
quiver conformal field theories with gravity duals, adding a chemical potential
for the R-charge leads to the existence of superfluid states in which a chiral
primary operator of the schematic form O = \lambda\lambda + W condenses. Here
\lambda is a gluino and W is the superpotential. Our argument is based on the
construction of a consistent truncation of type IIB supergravity that includes
a U(1) gauge field and a complex scalar.Comment: 5 pages, 2 figures; v2 improved figure, small change
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