Review of 'The Salati Case' by Tobias Jones.

Review of 'The Salati Case' by Tobias Jones

Constraints on WIMP Dark Matter from the High Energy PAMELA pˉ/p\bar{p}/p data

A new calculation of the $\bar{p}/p$ ratio in cosmic rays is compared to the recent PAMELA data. The good match up to 100 GeV allows to set constraints on exotic contributions from thermal WIMP dark matter candidates. We derive stringent limits on possible enhancements of the WIMP \pbar flux: a $m_{\rm WIMP}$=100 GeV (1 TeV) signal cannot be increased by more than a factor 6 (40) without overrunning PAMELA data. Annihilation through the $W^+W^-$ channel is also inspected and cross-checked with $e^+/(e^-+e^+)$ data. This scenario is strongly disfavored as it fails to simultaneously reproduce positron and antiproton measurements.Comment: 5 pages, 5 figures, the bibliography has been updated, minor modifications have been made in the tex

TeV cosmic-ray proton and helium spectra in the myriad model II

Recent observations show that the cosmic ray nuclei spectra start to harden above 100 GeV, in contradiction with the conventional steady-state cosmic ray model. We had suggested that this anomaly is due to the propagation effect of cosmic rays released from local young cosmic ray sources, the total flux of the cosmic ray should be computed with the myriad model, where contribution from sources in local catalog is added to the background. However, while the hardening could be elegantly explained in this model, the model parameters obtained from the fit skew toward a region with fast diffusion and low supernova rate in the Galaxy, in tension with other observations. In this paper, we further explore this model in order to set up a concordant picture. Two possible improvements related to the cosmic ray sources have been considered. Firstly, instead of the usual axisymmetric disk model, we considered a spiral model of source distribution. Secondly, for the nearby and young sources which are paramount to the hardening, we allow for an energy-dependent escape time. We find that major improvement comes from the energy-dependent escape time of the local sources, and with both modifications, not only the cosmic ray proton and helium anomalies are solved, but also the parameters attain reasonable range values compatible with other analysis.Comment: 13 pages, 7 figures, 1 table, accepted for publication in RA

The Cosmic Ray Signature of Dark Matter Caustics

Gravitational collapse of dark matter, merger of dark matter haloes and tidal disruption of satellites are among processes which lead to the formation of fine and dense dark matter shells, also known as dark matter caustics. The putative weakly interacting species which may form the dark matter are expected to strongly annihilate in these dense regions of the Milky Way halo and generate in particular antiprotons and positrons. We derive the flux of these rare antimatter particles at the Earth and show that it depends significantly on the cut-off radius of the dark matter distribution at the galactic centre. Boost factors of ~30 are found with respect to a smooth NFW profile for high-energy antiprotons and low-energy positrons if this cut-off radius is taken to be 300 pc -- a somewhat extreme value though. This yields a detectable antiproton signal around hundreds of Gev in models where the annihilation cross section today is enhanced by non--perturbative effects as in the generic case of a heavy Wino. However, dark matter caustics cannot provide a better explanation for the HEAT excess reported above ~10 GeV than a smooth NFW or isothermal cored distribution.Comment: 16 pages, 11 figures, version to appear in MNRA

Minimal Dark Matter predictions for galactic positrons, anti-protons, photons

We present the energy spectra of the fluxes of positrons, anti-protons and photons generated by Dark Matter annihilations in our galaxy, as univocally predicted by the model of Minimal Dark Matter. Due to multi-TeV masses and to the Sommerfeld enhancement of the annihilation cross section, distinctive signals are generated above the background, even with a modest astrophysical boost factor, in the range of energies soon to be explored by cosmic ray experiments.Comment: 16 pages, 6 figures, 3 tables of fit parameters. v3: in an addendum at page 17 we show that the Minimal Dark Matter prediction agrees with the anomaly in the positron spectrum announced by the PAMELA collaboratio

Intermediate Mass Black Holes and Nearby Dark Matter Point Sources: A Critical Reassessment

The proposal of a galactic population of intermediate mass black holes (IMBHs), forming dark matter (DM) ``mini-spikes'' around them, has received considerable attention in recent years. In fact, leading in some scenarios to large annihilation fluxes in gamma rays, neutrinos and charged cosmic rays, these objects are sometimes quoted as one of the most promising targets for indirect DM searches. In this letter, we apply a detailed statistical analysis to point out that the existing EGRET data already place very stringent limits on those scenarios, making it rather unlikely that any of these objects will be observed with, e.g., the Fermi/GLAST satellite or upcoming Air Cherenkov telescopes. We also demonstrate that prospects for observing signals in neutrinos or charged cosmic rays seem even worse. Finally, we address the question of whether the excess in the cosmic ray positron/electron flux recently reported by PAMELA/ATIC could be due to a nearby DM point source like a DM clump or mini-spike; gamma-ray bounds, as well as the recently released Fermi cosmic ray electron and positron data, again exclude such a possibility for conventional DM candidates, and strongly constrain it for DM purely annihilating into light leptons.Comment: 4 pages revtex4, 4 figures. Improved analysis and discussion, added constraints from Fermi data, corrected figures and updated reference

The Zero Age Main Sequence of WIMP burners

We modify a stellar structure code to estimate the effect upon the main sequence of the accretion of weakly interacting dark matter onto stars and its subsequent annihilation. The effect upon the stars depends upon whether the energy generation rate from dark matter annihilation is large enough to shut off the nuclear burning in the star. Main sequence WIMP burners look much like protostars moving on the Hayashi track, although they are in principle completely stable. We make some brief comments about where such stars could be found, how they might be observed and more detailed simulations which are currently in progress. Finally we comment on whether or not it is possible to link the paradoxically young OB stars found at the galactic centre with WIMP burners.Comment: 4 pages, 3 figs. Matches published versio

Brief History of Ultra-light Scalar Dark Matter Models

This is a review on the brief history of the scalar field dark matter model also known as fuzzy dark matter, BEC dark matter, wave dark matter, or ultra-light axion. In this model ultra-light scalar dark matter particles with mass $m = O(10^{-22})eV$ condense in a single Bose-Einstein condensate state and behave collectively like a classical wave. Galactic dark matter halos can be described as a self-gravitating coherent scalar field configuration called boson stars. At the scale larger than galaxies the dark matter acts like cold dark matter, while below the scale quantum pressure from the uncertainty principle suppresses the smaller structure formation so that it can resolve the small scale crisis of the conventional cold dark matter model.Comment: 5 page