1,132 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
Electroweak lights from Dark Matter annihilations
The energy spectra of Standard Model particles originated from Dark Matter
annihilations can be significantly altered by the inclusion of electroweak
gauge boson radiation from the final state. A situation where this effect is
particularly important is when a Majorana Dark Matter particle annihilates into
two light fermions. This process is in p-wave and hence suppressed by the small
value of the relative velocity of the annihilating particles. The inclusion of
electroweak radiation eludes this suppression and opens up a potentially
sizeable s-wave contribution to the annihilation cross section. I will discuss
the impact of this effect on the fluxes of stable particles resulting from the
Dark Matter annihilations, which are relevant for Dark Matter indirect
searches.Comment: 4 pages, 2 figures. Contribution to the conference proceedings of
TAUP 2011, Munich - Germany (5-9 September 2011
On Near-Linear-Time Algorithms for Dense Subset Sum
In the Subset Sum problem we are given a set of positive integers and a target and are asked whether some subset of sums to . Natural parameters for this problem that have been studied in the literature are and as well as the maximum input number and the sum of all input numbers . In this paper we study the dense case of Subset Sum, where all these parameters are polynomial in . In this regime, standard pseudo-polynomial algorithms solve Subset Sum in polynomial time . Our main question is: When can dense Subset Sum be solved in near-linear time ? We provide an essentially complete dichotomy by designing improved algorithms and proving conditional lower bounds, thereby determining essentially all settings of the parameters for which dense Subset Sum is in time . For notational convenience we assume without loss of generality that (as larger numbers can be ignored) and (using symmetry). Then our dichotomy reads as follows: - By reviving and improving an additive-combinatorics-based approach by Galil and Margalit [SICOMP'91], we show that Subset Sum is in near-linear time if . - We prove a matching conditional lower bound: If Subset Sum is in near-linear time for any setting with , then the Strong Exponential Time Hypothesis and the Strong k-Sum Hypothesis fail. We also generalize our algorithm from sets to multi-sets, albeit with non-matching upper and lower bounds
Half-integral weight p-adic coupling of weakly holomorphic and holomorphic modular forms
published_or_final_versio
Neutrino signals from electroweak bremsstrahlung in solar WIMP annihilation
Bremsstrahlung of and gauge bosons, or photons, can be an important
dark matter annihilation channel. In many popular models in which the
annihilation to a pair of light fermions is helicity suppressed, these
bremsstrahlung processes can lift the suppression and thus become the dominant
annihilation channels. The resulting dark matter annihilation products contain
a large, energetic, neutrino component. We consider solar WIMP annihilation in
the case where electroweak bremsstrahlung dominates, and calculate the
resulting neutrino spectra. The flux consists of primary neutrinos produced in
processes such as and , and secondary neutrinos produced via the decays of gauge
bosons and charged leptons. After dealing with the neutrino propagation and
flavour evolution in the Sun, we consider the prospects for detection in
neutrino experiments on Earth. By comparing our signal with that for
annihilation to , we show that the detection prospects for the
bremsstrahlung annihilation channel are favourable.Comment: 18 pages, 5 figures. Discussion expanded; matches published versio
New Gamma-Ray Contributions to Supersymmetric Dark Matter Annihilation
We compute the electromagnetic radiative corrections to all leading
annihilation processes which may occur in the Galactic dark matter halo, for
dark matter in the framework of supersymmetric extensions of the Standard Model
(MSSM and mSUGRA), and present the results of scans over the parameter space
that is consistent with present observational bounds on the dark matter density
of the Universe. Although these processes have previously been considered in
some special cases by various authors, our new general analysis shows novel
interesting results with large corrections that may be of importance, e.g., for
searches at the soon to be launched GLAST gamma-ray space telescope. In
particular, it is pointed out that regions of parameter space where there is a
near degeneracy between the dark matter neutralino and the tau sleptons,
radiative corrections may boost the gamma-ray yield by up to three or four
orders of magnitude, even for neutralino masses considerably below the TeV
scale, and will enhance the very characteristic signature of dark matter
annihilations, namely a sharp step at the mass of the dark matter particle.
Since this is a particularly interesting region for more constrained mSUGRA
models of supersymmetry, we use an extensive scan over this parameter space to
verify the significance of our findings. We also re-visit the direct
annihilation of neutralinos into photons and point out that, for a considerable
part of the parameter space, internal bremsstrahlung is more important for
indirect dark matter searches than line signals.Comment: Replaced Fig. 2c which by mistake displayed the same spectrum as Fig.
2d; the radiative corrections reported here are now implemented in DarkSUSY
which is available at http://www.physto.se/~edsjo/darksusy
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