Related papers: Ultra High Energy Cosmic Rays: The theoretical cha…
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…
The origin of cosmic rays is one of the major unresolved astrophysical questions. In particular, the highest energy cosmic rays observed possess macroscopic energies and their origin is likely to be associated with the most energetic…
The origin of cosmic rays with energies higher than 10$^{20}$ eV remains a mystery. Accelerating particles up to these energies is a challenge even for the most energetic astrophysical objects known. While the isotropy in arrival directions…
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…
The existence of cosmic rays of energies exceeding 10^20 eV is one of the mysteries of high energy astrophysics. The spectrum and the high energy to which it extends rule out almost all suggested source models. The challenges posed by…
A fundamental question that can be answered in the next decade is: WHAT IS THE ORIGIN OF THE HIGHEST ENERGY COSMIC PARTICLES? The discovery of the sources of the highest energy cosmic rays will reveal the workings of the most energetic…
We discuss the basic difficulties in understanding the origin of the highest energy particles in the Universe - the ultrahigh energy cosmic rays (UHECR). It is difficult to imagine the sources they are accelerated in. Because of the strong…
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…
One of the models recently proposed to explain the origin of the ultra high energy cosmic rays assumes that these particles may be accelerated by the electromotive force around presently inactive quasar remnants. We study predictions for…
Cosmic high energy neutrinos are inextricably linked to the origin of cosmic rays which is one of the major unresolved questions in astrophysics. In particular, the highest energy cosmic rays observed possess macroscopic energies and their…
We will discuss the main relevant aspects of the physics of ultra high energy cosmic rays. After a short recap of the experimental evidences, we will review theoretical models aiming at describing the sources of these extremely energetic…
The surprising lack of a high energy cutoff in the cosmic ray spectrum at the highest energies together with an apparently isotropic distribution of arrival directions have strongly challenged most models proposed for the acceleration of…
The lack of a high energy cutoff in the cosmic ray spectrum together with an apparently isotropic distribution of arrival directions for the highest energy events have strongly constrained most models proposed for the generation of these…
Significant progress has been made over the past decades towards unveiling the sources of the most energetic particles in nature, the ultra-high-energy cosmic rays (UHECRs). Despite these advancements, the exact astrophysical sites capable…
Recent international efforts have brought us closer to unveiling the century old mystery of the origin of cosmic rays. Cosmic ray, gamma ray, and neutrino observatories are reaching the necessary sensitivity to study the highest energy…
We review the physics of the highest energy cosmic rays. The discovery of their sources, still unknown, will reveal the most energetic astrophysical objects in the universe and could unveil new physics beyond the standard model of particle…
Origin of ultra high energy cosmic rays is an unsolved problem. Several proposals such as Z-burst, decay of super massive matter, susy particles as a primary, neutrino as a primary in extra dimension models exist in the literature which try…
We briefly discuss some open problems and recent developments in the investigation of the origin and propagation of ultra high energy cosmic rays (UHECRs).
The origin of the ultra high energy cosmic rays (UHECR) with energies above E > 1017eV, is still unknown. The discovery of their sources will reveal the engines of the most energetic astrophysical accelerators in the universe. This is a…
We briefly discuss three aspects related to the origin of ultra-high energy cosmic rays (UHECRs) namely: 1) particle acceleration in astrophysical sources; 2) transition to an extragalactic origin; 3) spectrum and anisotropies at the…