[en] The highest energy cosmic rays observed posses macroscopic energies and their origin is likely to be associated with the most energetic processes in the Universe. Their existence triggered a flurry of theoretical explanations ranging from conventional shock acceleration to particle physics beyond the Standard Model and processes taking place at the earliest moments of our Universe. Furthermore, many new experimental activities promise a strong increase of statistics at the highest energies and a combination with gamma-ray and neutrino astrophysics will put strong constraints on these theoretical models. Detailed Monte Carlo simulations indicate that charged ultra-high energy cosmic rays can also be used as probes of large scale magnetic fields whose origin may open another window into the very early Universe. We give an overview over this quickly evolving research field

[en] Historically cosmic rays have always been at the intersection of astrophysics with particle physics. This is still and especially true in current days where experimenters routinely observe atmospheric showers from particles whose energies reach macroscopic values up to about 50 J. This dwarfs energies achieved in the laboratory by about eight orders of magnitude in the detector frame and three orders of magnitude in the center of mass. While the existence of these highest energy cosmic rays does not necessarily testify physics not yet discovered, their macroscopic energies likely links their origin to the most energetic processes in the Universe. Explanations range from conventional shock acceleration to particle physics beyond the Standard Model and processes taking place at the earliest moments of our Universe. While motivation for some of the more exotic scenarios may have diminished by newest data, conventional shock acceleration scenarios remain to be challenged by the apparent isotropy of cosmic ray arrival directions which may not be easy to reconcile with a highly structured and magnetized Universe. Fortunately, many new experimental activities promise a strong increase of statistics at the highest energies and a combination with γ-ray and neutrino astrophysics will put strong constraints on all these theoretical models. This short review is far from complete and instead presents a selection of aspects regarded by the author as interesting and/or promising for the future

[en] Recently, a correlation of the arrival directions of ultra high energy cosmic rays (UHECR) with nearby AGN has been claimed. Most of these galaxies belong to the Local Supercluster (LSC) which is centered on the Virgo galaxy cluster. If indeed, UHECR are accelerated and confined to the LSC, gamma-rays and neutrinos are ideal probes to investigate its total cosmic ray content. We calculate the signatures of gamma-rays produced in proton-photon interactions modeling for the first time a realistic target photon field including the optical to far-infrared extragalactic radiation as well as the contribution of member galaxies in the super-cluster. The observable secondary particle spectra from the electromagnetic cascade are calculated and compared with existing observational constraints including gamma-ray, cosmic-ray, and neutrino measurements

[en] Most early universe scenarios predict negligible magnetic fields on cosmological scales if they are unprocessed during subsequent expansion of the universe. We present a new numerical treatment of the evolution of primordial fields and apply it to weakly helical seeds as they occur in certain early universe scenarios. If seed fields created during the electroweak phase transition have close to thermal strength and coherence lengths a few orders of magnitude below the horizon scale, initial helicities not much larger than the baryon to photon number can lead to fields of ∼10^-13 G at scales up to 100 parsec today

[en] We briefly review the current experimental and theoretical status of cosmic radiation above ∼10¹⁷ eV, including secondary neutrinos and gamma-rays. We focus on questions related to chemical composition and sky distributions of these particles as well as on the location and nature of their sources.

[en] An analysis of the Fermi LAT data has recently revealed a resolved gamma-ray feature close to the galactic center which is consistent with monochromatic photons at an energy of about 130 GeV. If interpreted in terms of DM annihilating into gamma gamma (gamma Z, gamma h), this would correspond to a DM particle mass of roughly 130 GeV (145 GeV-155 GeV). The rate for these loop-suppressed processes, however, is larger than typically expected for thermally produced DM. Correspondingly, one would generically expect even larger tree level production rates of standard model fermions or gauge bosons. Here, we quantify this expectation in a rather model-independent way by relating the tree level and loop amplitudes with the help of the optical theorem. As an application, we consider bounds from continuum gamma rays, radio and antiproton data on the tree level amplitudes and translate them into constraints on the loop amplitudes. We find that, independently of the DM production mechanism, any DM model aiming at explaining the line signal in terms of charged standard model particles running in the loop is in rather strong tension with at least one of these constraints, with the exception of loops dominated by top quarks. We stress that attempts to explain the 130 GeV feature with internal bremsstrahlung do not suffer from such difficulties.

[en] CRPropa 1.4 is a publicly available tool to study the propagation of ultra high energy nucleons in extra galactic environments. It considers reactions with low energy photon fields and the influence of deflections in extra galactic magnetic fields. But, current experimental data indicate that heavy nuclei may contribute to the flux of ultra-high energy cosmic rays. Thus, to understand the effects of their propagation on the observed spectrum and mass composition, CRPropa 1.4 has been extended to allow for the propagation of nuclei. It takes into account photodisintigration and pion production in ambient photon fields, as well as the decay of unstable nuclei created in these reactions. Additionally, pair production is taken into account as an continuous energy loss. A beta version of CRPropa 2.0 was released in the beginning of 2011. In this talk, we present the nuclei extensions of CRPropa 2.0 and discuss first simulation results.

No abstract available

[en] If dark matter decays into electrons and positrons, it can affect Galactic radio emissions and the local cosmic ray fluxes. We propose a new, more general analysis of constraints on dark matter. The constraints can be obtained for any decaying dark matter model by convolving the specific dark matter decay spectrum with a response function. We derive this response function from full-sky radio surveys at 408 MHz, 1.42 GHz and 23 GHz, as well as from the positron flux recently reported by PAMELA. We discuss the influence of astrophysical uncertainties on the response function, such as from propagation and from the profiles of the dark matter and the Galactic magnetic field. As an application, we find that some widely used dark matter decay scenarios can be ruled out under modest assumptions. (orig.)

[en] High energy electrons and positrons from annihilating dark matter can imprint unique angular anisotropies on the diffuse gamma-ray flux by inverse Compton scattering off the interstellar radiation field. We develop a numerical tool to compute gamma-ray emission from such electrons and positrons diffusing in the smooth host halo and in substructure halos with masses down to 10^-6M_sun. We show that, unlike the total gamma-ray angular power spectrum observed by Fermi-LAT, the angular power spectrum from inverse Compton scattering is exponentially suppressed below an angular scale determined by the diffusion length of electrons and positrons. For TeV scale dark matter with a canonical thermal freeze-out cross section 3 x 10^-26 cm³/s, this feature may be detectable by Fermi-LAT in the energy range 100-300 GeV after more sophisticated foreground subtraction. We also find that the total flux and the shape of the angular power spectrum depends sensitively on the spatial distribution of subhalos in the Milky Way. Finally, the contribution from the smooth host halo component to the gamma-ray mean intensity is negligibly small compared to subhalos. (orig.)