Related papers: Evidence for an axion-like particle from blazar sp…
Recent detection of blazar 3C279 by MAGIC has confirmed previous indications by H.E.S.S. that the Universe is more transparent to very-high-energy gamma rays than currently thought. This circumstance can be reconciled with observations of…
Recent observations by H.E.S.S. and MAGIC strongly suggest that the Universe is more transparent to very-high-energy gamma rays than previously thought. We show that this fact can be reconciled with standard blazar emission models provided…
Early indications by H.E.S.S. and the subsequent detection of blazar 3C279 by MAGIC show that the Universe is more transparent to very-high-energy gamma rays than previously thought. We demonstrate that this circumstance can be reconciled…
Recent findings by gamma-ray Cherenkov telescopes suggest a higher transparency of the Universe to very-high-energy (VHE) photons than expected from current models of the Extragalactic Background Light. It has been shown that such…
The recent detection of blazar 3C279 by MAGIC has confirmed previous indications by H.E.S.S. that the Universe is more transparent to very-high-energy gamma rays than previously thought. We show that this fact can be reconciled with…
An anomalously large transparency of the Universe to gamma rays has recently been discovered by the Imaging Atmospheric Cherenkov Telescopes (IACTs) H.E.S.S. and MAGIC. We show that observations can be reconciled with standard blazar…
As very high energy (~100 GeV) gamma rays travel over cosmological distances, their flux is attenuated through interactions with the extragalactic background light. Observations of distant gamma ray sources at energies between ~200 GeV and…
Recent findings by Imaging Atmospheric Cherenkov Telescopes indicate a large transparency of the Universe to gamma rays, which can be hardly explained within the current models of extragalactic background light. We show that the observed…
Several extensions of the Standard Model predict the existence of Axion-Like Particles (ALPs), very light spin-zero bosons with a two-photon coupling. ALPs can give rise to observable effects in very-high-energy astrophysics. Above roughly…
The Universe opacity to gamma rays is still an open question, in particular anomalies may have been observed. Assuming that such anomalies find their origin in conventional physics like intrinsic source spectra or the density of the…
We propose that axion-like particles (ALPs) with a two-photon vertex, consistent with all astrophysical and laboratory bounds, may lead to a detectable signature in the spectra of high-energy gamma ray sources. This occurs as a result of…
Very high energy (VHE, energy >~ 100 GeV) {\gamma}-rays undergo pair production with photons of the extragalactic background light (EBL). Thus, the intrinsic {\gamma}-ray flux of cosmological sources is attenuated and the Universe should be…
The atmospheric Cherenkov gamma-ray telescope MAGIC, designed for a low-energy threshold, has detected very-high-energy gamma rays from a giant flare of the distant Quasi-Stellar Radio Source (in short: radio quasar) 3C 279, at a distance…
Axionlike particles (ALPs) are a common prediction of theories beyond the Standard Model of particle physics that could explain the entirety of the cold dark matter. These particles could be detected through their mixing with photons in…
Axion-like particles (ALPs) are attracting increasing interest since, among other things, they are a prediction of many extensions of the standard model of elementary particles physics and in particular of superstrings and superbranes.…
The idea that photons can convert into axion-like particles (ALPs) $\gamma \to a$ in or around an AGN and reconvert back into photons $a \to \gamma$ in the Milky Way magnetic field has been put forward in 2008 and has recently attracted…
Many extensions of the Standard Model predict the existence of ALPs, which are very light spin-zero bosons with a two-photon coupling. Photon-ALP oscillations occur in the presence of an external magnetic field, and ALPs can lead to…
The intrinsic flux of very high energy (VHE, Energy > 100 GeV) gamma-rays from extragalactic sources is attenuated due to pair production in the interaction with photons of the extragalactic background light (EBL). Depending on the distance…
The propagation of very high energy gamma-rays ($E>100$~GeV) over cosmological distances is suppressed by pair-production processes with the ubiquitous extra-galactic soft photon background, mainly in the optical to near infra-red. The…
In this mini-review, possible manifestations of mixing between axion-like particles (ALPs) and energetic photons propagating over astronomical distances are considered. We discuss the evidence for the anomalous transparency of the Universe…