Related papers: Lorentz violation from cosmological objects with v…
The Lorentz invariance violation (LIV) predicted by some quantum gravity theories would manifest as an energy-dependent speed of light, which may potentially distort the observed temporal profile of photons from astrophysical sources at…
The blazar Mrk 501 (z=0.034) was observed at very-high-energy (VHE, $E\gtrsim 100$~GeV) gamma-ray wavelengths during a bright flare on the night of 2014 June 23-24 (MJD 56832) with the H.E.S.S. phase-II array of Cherenkov telescopes. Data…
The Lorentz factor (LF) of gamma-ray burst (GRB) ejecta may be constrained by observations of high-energy (HE) spectral attenuation. The recent Fermi-LAT observations of prompt GeV emission from several bright GRBs have leaded to…
In recent years, Lorentz violation (LV) has emerged as a vibrant area of research in fundamental physics. Despite predictions from quantum gravity theories that Lorentz symmetry may break down at Planck-scale energies, which are currently…
Gravitational lensing of very high energy photons has recently been observed in the JVAS B0218+357 strong lensing system. This observation opens the possibility of performing a test of gravity at high energy by comparing the difference in…
Recent observations by the Fermi-LAT showed that there are delayed arrivals of GeV photons relative to the onset of MeV photons in some GRBs. In order to avoid a large optical depth, the minimal value of the Lorentz factor has been…
Positive lags between the arrival time of different photon energies are commonly observed in Gamma-Ray Bursts (GRBs), where soft photons lag behind harder ones. However, some GRBs exhibit the opposite behavior. In particular, Fermi LAT…
Violations of Lorentz invariance can lead to an energy-dependent vacuum dispersion of light, which results in arrival-time differences of photons arising with different energies from a given transient source. In this work,…
We discuss the prospects for bounding and perhaps even measuring quantum gravity effects on the dispersion of light using the highest energy photons produced in gamma ray bursts measured by the Fermi telescope. These prospects are brigher…
We investigate the impact of Lorentz invariance violation (LIV) on radiation processes in astrophysical sources, focusing on synchrotron and inverse Compton interactions. We derive modified expressions for radiated power and photon energy…
Possible violations of Lorentz invariance (LIV) have been investigated for a long time using the observed spectral lags of gamma-ray bursts (GRBs). However, these generally have relied on using a single photon in the highest energy range.…
From special relativity, photon annihilation process \HepProcess{{\Pgg}{\Pgg}{\to}{\Pep}{\Pem}} prevents cosmic photons with energies above a threshold to propagate a long distance in cosmic space due to their annihilation with low energy…
Before the launch of the Fermi Gamma-ray Space Telescope there were only a handful of gamma-ray bursts (GRBs) detected at high energies (above 100 MeV), while several different suggestions have been made for possible high-energy emission…
We discuss possible tests of the constancy of the velocity of light using distant astrophysical sources such as gamma-ray bursters (GRBs), Active Galactic Nuclei (AGNs) and pulsars. This speculative quest may be motivated by some models of…
Cosmic opacity for very high-energy gamma rays ($E>10$ TeV) due to the interaction with the extragalactic background light can be strongly reduced because of possible Lorentz-violating terms in the particle dispersion relations expected,…
Lorentz invariance violation (LIV) introduced as a generic modification to particle dispersion relations can change the photon energy threshold of pair-production, which modifies the expected gamma-ray flux from astrophysical sources. In…
Ultrahigh energy cosmic rays that produce giant extensive showers of charged particles and photons when they interact in the Earth's atmosphere provide a unique tool to search for new physics. Of particular interest is the possibility of…
Fast variations of gamma-ray flux from Active Galactic Nuclei and Gamma-Ray Bursts can constrain Lorentz Invariance Violation (LIV) because of the delayed (or advanced) arrival of photons with higher energies: this approach has lead to the…
The Large High Altitude Air Shower Observatory~(LHAASO) is one of the most sensitive gamma-ray detector arrays currently operating at TeV and PeV energies. Recently the LHAASO experiment detected ultra-high-energy~(UHE; $E_{\gamma}\gtrsim…
Lorentz invariance violation (LIV) can manifest itself by an energy-dependent vacuum dispersion of light, which leads to arrival-time differences of photons with different energies originating from the same astronomical source. The spectral…