相关论文: Limits on Topological Defects Models of the Ultrah…
We give an overview over models in which cosmic rays above 1 EeV = 10**(18) eV are produced by the decay of supermassive "X" particles released from topological defects possibly created in cosmological phase transitions. We note that, for…
The topological defect scenario of origin of the observed highest energy cosmic rays is reviewed. Under a variety of circumstances, topological defects formed in the early Universe can be sources of very massive particles in the Universe…
In this paper we review the hypothesis that a considerable part of the cosmic ray flux observed above about $10^{19}\eV$ may be produced by decaying or annihilating topological defects left over from phase transitions in the early universe…
The origin of the highest-energy cosmic rays remains a mystery. The lack of a high energy cutoff in the cosmic ray spectrum together with an apparently isotropic distribution of arrival directions have strongly constrained most models…
Cosmic ray particles with energies in excess of 10**(20) eV have been detected. The sources as well as the physical mechanism(s) responsible for endowing cosmic ray particles with such enormous energies are unknown. This report gives a…
The origin of cosmic rays is one of the major unresolved questions in astrophysics. In particular, the highest energy cosmic rays observed possess macroscopic energies and their origin is likely associated with the most energetic processes…
Diffuse ultrahigh energy gamma-radiation can arise from a variety of astrophysical sources, including the interaction of extremely high energy cosmic rays with the 3K microwave background radiation or the collapse of topological defects…
Extragalactic and galactic cosmic rays scatter with the cosmic neutrino background during propagation to Earth, yielding a flux of relic neutrinos boosted to larger energies. If an overdensity of relic neutrinos is present in galaxies, and…
We discuss theoretical issues and experimental data that brought the ultra high energy cosmic rays in the list of Nature's greatest puzzles. After many years of research we still do not know how astrophysical acceleration processes can…
The existence of cosmic ray particles up to the ultra-high energy limit (> 10^20 eV) is now beyond any doubt. The detection of cosmic particles with such energies imposes a challenge for the comprehension of their sources and nature. On one…
Ultra-high energy cosmic rays interacting with the radiation fields in the universe cause electromagnetic cascades resulting in a flux of extragalactic gamma rays, detectable to some 100 GeV. Recent precise measurements of the extragalactic…
The origin of the highest energy cosmic rays is still unknown. The discovery of their sources will reveal the workings of the most energetic astrophysical accelerators in the universe. Current observations show a spectrum consistent with an…
Under the assumption that some part of the observed highest energy cosmic rays consists of protons originating from cosmological distances, we derive bounds on the associated flux of neutrinos generated by inelastic processes with the…
We address some current theoretical issues around ultra-high energy cosmic rays. We recall that scenarios producing more gamma-rays than cosmic rays up to high redshift can in general only provide a sub-dominant contribution to the…
More than 100 years after the discovery of cosmic rays and various experimental efforts, the origin of ultra-high energy cosmic rays (E > 100 PeV) remains unclear. The understanding of production and propagation effects of these highest…
In this paper we briefly discuss the problem of the origin of Ultra High Energy Cosmic Rays in the framework of Top-Down models. We show that, for high energy of decays and in a wide range of spectra of injected protons, their extragalactic…
The origin of the particles in the highest energy end of the cosmic ray spectrum is discussed in the context of the wider problem of the origin of the whole cosmic radiation as observed at the Earth. In particular we focus our attention on…
We use of a hybrid matrix--Monte Carlo method to simulate the cascade through the cosmic background radiation initiated by UHE particles and radiation emitted by topological defects. We follow the cascade over cosmological distances and…
It is pointed out that the observed extremely high energy cosmic rays (EHECR) above $10^{11}$ GeV and the observed baryon asymmetry of the Universe (BAU), both may have a common origin in baryon number violating decays of supermassive ``X''…
In a recently proposed model the cosmic rays spectrum at energies above EeV can be fitted with a minimal number of unknown parameters assuming that the extragalactic cosmic rays are only protons with a power law source spectrum. Within this…