Related papers: Stable Superstring Relics and Ultrahigh Energy Cos…
We investigate the cosmological constraints on exotic stable matter states which arise in realistic free fermionic superstring models. These states appear in the superstring models due to a ``Wilson--line'' breaking of the unifying…
Cryptons are metastable bound states of fractionally-charged particles that arise generically in the hidden sectors of models derived from heterotic string. We study their properties and decay modes in a specific flipped SU(5) model with…
Superstring theory predicts the existence of relic metastable particles whose average lifetime is longer than the age of the universe and which could, in principle, be good dark matter candidates. At the same time, these states would be…
The dark matter issue is among the most perplexing in contemporary physics. The problem is more enigmatic due to the wide range of possible solutions, ranging from the ultra-light to the super-massive. String theory gives rise to plausible…
The clustering of ultra high energy (above 5\cdot 10^{19} eV) cosmic rays (UHECR) suggests that they might be emitted by compact sources. We present a statistical analysis on the source density based on the multiplicities. The propagation…
We calculate the spectra of ultra-high-energy cosmic rays (UHECRs) in an explicit top-down model based on the decays of metastable neutral `crypton' states in a flipped SU(5) string model. For each of the eight specific 10th-order…
The Ultra High Energy Cosmic Ray (UHECR), by UHE neutrino-relic neutrino--Z showering in Hot Dark Halos (HDM), shows an energy spectra, an anisotropy following the relic neutrino masses and clustering in dark halo. The lighter are the relic…
Cryptons, metastable bound states of matter in the string hidden sector, with dynamically determined masses M_X on the order of 10^{12} GeV and lifetimes tau_X greater than or on the order of 10^{18} yr, may be generated, through inflation,…
The current status of origin of Ultra High Energy Cosmic Rays (UHECR) is reviewed, with emphasis given to elementary particle solutions to UHECR problem, namely to Topological Defects and Super-Heavy Dark Matter (SHDM) particles. The relic…
We reconsider superheavy dark matter candidates in string and M theory, in view of the possibility that inflation might generate superheavy particles with an abundance close to that required for a near-critical Universe. We argue that…
Ultra high energy cosmic rays (UHECR) pose a problem either for particle physics or for astrophysics (or for both) by the unexpectedly high number of cosmic ray showers observed with energy above about 5x10^{19}eV, the…
The origin of highest energy cosmic rays (UHECR) is yet unknown. In order to understand their propagation we determine the probability that an ultrahigh energy (above 5\cdot 10^{19} eV) proton created at a distance r with energy E arrives…
Stable Superstring Relics (SSR) provide some of the candidates for the possible origin of the Ultra High Energy Cosmic Rays (UHECR). After a brief overview of the motivations for introducing such relics, we address the question whether…
We argue that the superheavy gravitinos that we had previously proposed as candidates for Dark Matter can offer a possible explanation for the ultra-high energy cosmic ray (UHECR) events observed at the Pierre Auger Observatory, via…
The Ultra High Energy (UHE) neutrino scattering onto relic cosmic neutrinos in galactic and local halos offers an unique way to overcome GZK cut-off. The UHE nu secondary of UHE photo-pion decays may escape the GZK cut-off and travel on…
The status of the Greisen-Zatsepin-Kuzmin (GZK) cutoff and pair-production dip in Ultra High Energy Cosmic Rays (UHECR) is discussed.They are the features in the spectrum of protons propagating through CMB radiation in extragalactic space,…
It is not yet clear whether the observed flux suppression for ultra-high energy cosmic rays (UHECR) at energies above \simeq 4.10E19 eV is a signature of the Greisen-Zatsepin-Kuzmin (GZK) cutoff or corresponds, for instance, to the maximum…
We argue that an astrophysical solution to UHECR problem is viable. The pectral features of extragalactic protons interacting with CMB are calculated in model-independent way. Using the power-law generation spectrum $\propto E^{-\gamma_g}$…
Ultra-high energy cosmic ray (UHECR) protons produced by uniformly distributed astrophysical sources contradict the energy spectrum measured by both the AGASA and HiRes experiments, assuming the small scale clustering of UHECR observed by…
The decay of very heavy metastable relics of the Early Universe can produce ultra-high energy cosmic rays (UHECRs) in the halo of our own Galaxy. On distance scales of the order of the halo size, energy losses are negligible---no…