Related papers: Probing The Structure of Space-Time with Cosmic Ra…
The energy densities in magnetic fields and cosmic rays (CRs) in galaxies are often assumed to be in equipartition, allowing for an indirect estimate of the magnetic field strength from the observed radio synchrotron spectrum. However, both…
We discuss the cosmological implications of an extended Brans-Dicke theory presented recently, in which there is an energy exchange between the scalar field and ordinary matter, determined by the theory. A new mass scale is generated in the…
We re-visit the production of cosmic rays by cusps on cosmic strings. If a scalar field (``Higgs'') has a linear interaction with the string world-sheet, such as would occur if there is a bosonic condensate on the string, cusps on string…
In the last years the direct measurement of cosmic rays received a push forward by the possibility of conducting experiments on board long duration balloon flights, satellites and on the International Space Station. The increase in the…
Recent years have seen many arguments for cosmic rays (CRs) as an important influence on galactic and circumgalactic (CGM) physics, star and galaxy formation. We present a pedagogical overview of state-of-the-art modeling of…
Interactions of grazing incidence, ultra high energy cosmic rays with the earth's atmosphere may provide a new method of studying energetic cosmic rays with gamma-ray satellites. It is found that these cosmic ray interactions may produce…
We explore scenarios where the highest energy cosmic rays (HECR) are produced by new particle physics near the grand unification scale. Using detailed numerical simulations of extragalactic cosmic and gamma-ray propagation, we show the…
We present here the transformations required to recast the Robertson-Walker metric and Friedmann-Robertson-Walker equations in terms of observer-dependent coordinates for several commonly assumed cosmologies. The overriding motivation is…
Possible violations of fundamental physical principles, e.g. the Einstein equivalence prin- ciple on which all metric theories of gravity are based, including general relativity (GR), would lead to a rotation of the plane of polarization…
New physics beyond the electroweak scale may increase weak interaction cross sections beyond the Standard Model predictions. Such cross sections can be expected within theories that solve the hierarchy problem of known interactions with a…
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…
A general view is presented on the problem of propagation of ultra high-energy cosmic rays through the intergalactic and galactic magnetic fields. Especial emphasis is given to the possibility of correlating the present events with…
The understanding of the nature of ultra-high-energy cosmic rays is one of the most intriguing open questions for current and future observatories. These particles are expected to be accelerated in extragalactic sources. Because of their…
Gamma-ray bursts (GRBs) have long been considered as candidates of ultrahigh-energy cosmic rays (UHECRs). We investigate the signatures of CR proton acceleration in the GRBs by consistently taking into account their hadronic and…
Cosmic rays with energies above $10^{18}$ eV are currently of considerable interest in astrophysics and are to be further studied in a number of projects which are either currently under construction or the subject of well-developed…
Excess emission over expected diffuse astrophysical backgrounds in the direction of the Galactic center region has been claimed at various wavelengths, from radio to gamma rays. Among particle models advocated to explain such observations,…
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…
Various aspects of the connection between cloud cover (CC) and cosmic rays (CR) are analysed. We argue that the anticorrelation between the temporal behaviour of low (LCC) and middle (MCC) clouds evidences against causal connection between…
Experimental results on ultra-high-energy cosmic rays are briefly reviewed and their interpretation is discussed. The results related to principal observables (arrival directions, energies and composition) of primary particles of extended…
Cosmological observations usually map our present-day past light cone. However, it is also possible to compare different past light cones. This is the concept behind the redshift drift, a model-independent probe of fundamental cosmology. In…