Related papers: Extragalactic TeV Photons and the Zero-point Vibra…
Here is reviewed our current understanding of Galactic and extragalactic diffuse gamma-ray emission. The spectrum of the extragalactic gamma-ray background above 30 MeV can be well described by a power law with photon index s=2.1. In the…
Very high energy (~ TeV) $\gamma$-rays from blazars are attenuated by photons from the extragalactic background light (EBL). Observations of blazars can therefore provide an ideal opportunity for determining the EBL intensity if their…
The extragalactic background light (EBL) is the aggregate of all optical and infrared emissions from thermal processes since the cosmic dark ages. While the integrated light of galaxies is expected to be the main contribution to the EBL,…
Cosmic topological defects in a wide class of supersymmetric theories can simultaneously be sources of higgs particles of mass comparable to the supersymmetry breaking scale $\sim$ TeV, as well as superheavy gauge bosons of mass $\sim\eta$,…
The recent HEGRA observations of the blazar Mkn 501 show strong curvature in the very high energy gamma-ray spectrum. Applying the gamma-ray opacity derived from an empirically based model of the intergalactic infrared background radiation…
We propose a model where a supernova explodes in some vicinity of our solar system (some tens of parsecs) in the recent past (some tens of thousands years) with the energy release in cosmic rays of order of $ 10 ^ {51} $ erg. The flux from…
In addition to its relevant astrophysical and cosmological significance, the Extragalactic Background Light (EBL) is a fundamental source of opacity for cosmic high energy photons, as well as a limitation for the propagation of high-energy…
The detection of TeV gamma-rays from the blazar H 1426+428 at an integral flux level of (4 +- 2(stat) +- 1(syst)) 10^(-12) erg cm^(-2) s^(-1) above 1 TeV with the HEGRA imaging atmospheric Cherenkov telescope system is reported. H 1426+428…
The interaction of TeV photons from blazars with the extragalactic background light produces a relativistic beam of electron-positron pairs streaming through the intergalactic medium (IGM). The fate of the beam energy is uncertain. By means…
The extragalactic background light (EBL) is one of the fundamental observational quantities in cosmology. All energy releases from resolved and unresolved extragalactic sources, and the light from any truly diffuse background, excluding the…
The intergalactic magnetic field (IGMF) in cosmic voids can be indirectly probed through its effect on electromagnetic cascades initiated by a source of TeV gamma rays, such as blazars, a subclass of active galactic nuclei. Blazars that are…
An intergalactic magnetic field stronger than $3\times10^{-13}$~G would explain the lack of a bright, extended degree-scale, GeV-energy inverse Compton component in the gamma-ray spectra of TeV-blazars. A robustly predicted consequence of…
The extragalactic background light (EBL), the cumulative radiation from all extragalactic sources, traces galaxy formation and cosmic evolution. High-energy $\gamma$ rays attenuated via pair production with EBL photons are a powerful probe…
The only invariant speed in special relativity is c; therefore, if some neutrinos travel at even tiny speeds above c, normal special relativity is incomplete and any superluminal speed may be possible. I derive a limit on superluminal…
Very high energy (VHE, energy $E \gtrsim 100$\,GeV) \gamma-rays from cosmological sources are attenuated due to the interaction with photons of the extragalactic background light (EBL) in the ultraviolet to infrared wavelength band. The…
Several high-frequency peaked BL Lac objects such as Mrk 501 are strong TeV emitters. However, a significant fraction of the TeV gamma rays emitted are likely to be absorbed in interactions with the diffuse IR background, yielding…
Axion-like particles (ALPs) can oscillate to photons and vice versa in electromagnetic fields. The photon-ALP oscillation provides an attractive solution to the apparent transparency of the Universe to TeV photons. The allowed parameter…
We analyze observational constraints from TeV astrophysics on Lorentz violating nonlinear dispersion for photons and electrons without assuming any a priori equality between the photon and electron parameters. The constraints arise from…
If dark matter is unstable and the mass is within GeV-TeV regime, its decays produce high-energy photons that give contribution to the extragalactic gamma-ray background (EGRB). We constrain dark matter decay by analyzing the 50-month EGRB…
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…