Spectral cutoffs in indirect dark matter searches

Indirect searches for dark matter annihilation or decay products in the cosmic-ray spectrum are plagued by the question of how to disentangle a dark matter signal from the omnipresent astrophysical background. One of the practically background-free smoking-gun signatures for dark matter would be the observation of a sharp cutoff or a pronounced bump in the gamma-ray energy spectrum. Such features are generically produced in many dark matter models by internal Bremsstrahlung, and they can be treated in a similar manner as the traditionally looked-for gamma-ray lines. Here, we discuss prospects for seeing such features with present and future Atmospheric Cherenkov Telescopes.Comment: 4 pages, 2 figures, 1 table; conference proceedings for TAUP 2011, Munich 5-9 Se

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

Inflation in Gauged 6D Supergravity

In this note we demonstrate that chaotic inflation can naturally be realized in the context of an anomaly free minimal gauged supergravity in D=6 which has recently been the focus of some attention. This particular model has a unique maximally symmetric ground state solution, $R^{3,1} \times S^2$ which leaves half of the six-dimensional supersymmetries unbroken. In this model, the inflaton field $\phi$ originates from the complex scalar fields in the D=6 scalar hypermultiplet. The mass and the self couplings of the scalar field are dictated by the D=6 Lagrangian. The scalar potential has an absolute munimum at $\phi = 0$ with no undetermined moduli fields. Imposing a mild bound on the radius of $S^2$ enables us to obtain chaotic inflation. The low eenrgy equations of motion are shown to be consistent for the range of scalar field values relevant for inflation.Comment: one reference adde

Constraints on small-scale cosmological perturbations from gamma-ray searches for dark matter

Events like inflation or phase transitions can produce large density perturbations on very small scales in the early Universe. Probes of small scales are therefore useful for e.g. discriminating between inflationary models. Until recently, the only such constraint came from non-observation of primordial black holes (PBHs), associated with the largest perturbations. Moderate-amplitude perturbations can collapse shortly after matter-radiation equality to form ultracompact minihalos (UCMHs) of dark matter, in far greater abundance than PBHs. If dark matter self-annihilates, UCMHs become excellent targets for indirect detection. Here we discuss the gamma-ray fluxes expected from UCMHs, the prospects of observing them with gamma-ray telescopes, and limits upon the primordial power spectrum derived from their non-observation by the Fermi Large Area Space Telescope.Comment: 4 pages, 3 figures. To appear in J Phys Conf Series (Proceedings of TAUP 2011, Munich

Disentangling Instrumental Features of the 130 GeV Fermi Line

We study the instrumental features of photons from the peak observed at $E_\gamma=130$ GeV in the spectrum of Fermi-LAT data. We use the {\sc sPlots} algorithm to reconstruct -- seperately for the photons in the peak and for background photons -- the distributions of incident angles, the recorded time, features of the spacecraft position, the zenith angles, the conversion type and details of the energy and direction reconstruction. The presence of a striking feature or cluster in such a variable would suggest an instrumental cause for the peak. In the publically available data, we find several suggestive features which may inform further studies by instrumental experts, though the size of the signal sample is too small to draw statistically significant conclusions.Comment: 9 pages, 22 figures; this version includes additional variables, study of stat sensitivity, and modification to the chi-sq calculatio

Cosmological constraints on dark matter models with velocity-dependent annihilation cross section

We derive cosmological constraints on the annihilation cross section of dark matter with velocity-dependent structure, motivated by annihilating dark matter models through Sommerfeld or Breit-Wigner enhancement mechanisms. In models with annihilation cross section increasing with decreasing dark matter velocity, big-bang nucleosynthesis and cosmic microwave background give stringent constraints.Comment: 23 pages, 9 figures; Added reference

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

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

Hecke-type double sums, Appell-Lerch sums, and mock theta functions (I)

By developing a connection between partial theta functions and Appell-Lerch sums, we find and prove a formula which expresses Hecke-type double sums in terms of Appell-Lerch sums and theta functions. Not only does our formula prove classical Hecke-type double sum identities such as those found in work Kac and Peterson on affine Lie Algebras and Hecke modular forms, but once we have the Hecke-type forms for Ramanujan's mock theta functions our formula gives straightforward proofs of many of the classical mock theta function identities. In particular, we obtain a new proof of the mock theta conjectures. Our formula also applies to positive-level string functions associated with admissable representations of the affine Lie Algebra $A_1^{(1)}$ as introduced by Kac and Wakimoto