This article reviews many of the observational constraints on Lorentz symmetry violation (LV). We first describe the GZK cutoff and other phenomena that are sensitive to LV. After a brief historical sketch of research on LV, we discuss the effective field theory description of LV and related questions of principle, technical results, and observational constraints. We focus on constraints from h...

In a gravitationally unstable universe, the structure of dark matter and galaxies, intergalactic gas and magnetic field can have severe impact on the propagation of ultra high energy cosmic rays (UHECR). The possible effects include spatial confinement and directional focusing along the supergalactic matter sheets, as well as universal re-acceleration at large scale shock fronts, and spectral m...

After a century of observations, we still do not know the origin of cosmic rays. I will review the current state of cosmic ray observations at the highest energies, and their implications for proposed acceleration models and secondary astroparticle fluxes. Possible sources have narrowed down with the confirmation of a GZK-like spectral feature. The anisotropy observed by the Pierre Auger Observ...

Cosmic ray events above 10 eV have posed a fundamental problem for more than thirty years. Recent measurements indicate that these events do not show the features predicted by the GZK bound. The events may, in addition, display angular correlations with points sources. If these observations are confirmed for point sources further than 50-100Mpc, then strong interactions for the ultra-high energ...

The intimate geometry of space-time is expected to suffer stochastic fluctuations as a result of quantum gravitational effects. These fluctuations may induce observable consequences on the propagation of high energy particles over large distances, so that the strength and the characteristics of these fluctuations may be constrained, mainly in the range of energies of interest for cosmic ray phy...

We discuss candidates for trans-GZK cosmic rays observed in a variety of detectors. Three types of primaries are represented among the abstracts submitted to this meeting: neutrinos causing a Z-burst, protons arising from the decay of ultra-heavy metastable particles and neutrinos within the framework of low scale string-like models of unification. We attempt to evaluate the relative merits of ...

We propose a new method for the estimation of ultra-high energy cosmic ray (UHECR) mass composition from distribution their arrival directions. The employs test statistic (TS) based on characteristic deflection UHECR events with respect to luminous matter in local Universe. Making realistic simulations mock sets, we show that this TS is robust presence galactic and non-extreme extra-galactic ma...

When propagating to Earth, UHECRs can interact with the gas in our Milky Way and produce secondary particles including photons. This impact search for UHE photons as we face a diffuse flux of resulting from their propagation. flux, together photon expected GZK interactions, participates which is limiting detection UHE-gamma sources. We present an estimate interactions galaxy above 10 17 eV, usi...