3,080 research outputs found
Derivation of a Relation for the Steepening of TeV Selected Blazar Gamma-ray Spectra with Energy and Redshift
We derive a relation for the steepening of blazar gamma-ray spectra between
the multi-GeV Fermi energy range and the TeV energy range observed by
atmospheric Cerenkov telescopes. The change in spectral index is produced by
two effects: (1) an intrinsic steepening, independent of redshift, owing to the
properties of emission and absorption in the source, and (2) a
redshift-dependent steepening produced by intergalactic pair production
interactions of blazar gamma-rays with low energy photons of the intergalactic
background light (IBL). Given this relation, with good enough data on the mean
gamma-ray SED of TeV selected BL Lacs, the redshift evolution of the IBL can,
in principle, be determined independently of stellar evolution models. We apply
our relation to the results of new Fermi observations of TeV selected blazars.Comment: Version to be published in the Astrophysical Journal Letter
Testing Lorentz Invariance with Neutrinos from Ultrahigh Energy Cosmic Ray Interactions
We have previously shown that a very small amount of Lorentz invariance
violation (LIV), which suppresses photomeson interactions of ultrahigh energy
cosmic rays (UHECRs) with cosmic background radiation (CBR) photons, can
produce a spectrum of cosmic rays that is consistent with that currently
observed by the Pierre Auger Observatory (PAO) and HiRes experiments. Here, we
calculate the corresponding flux of high energy neutrinos generated by the
propagation of UHECR protons through the CBR in the presence of LIV. We find
that LIV produces a reduction in the flux of the highest energy neutrinos and a
reduction in the energy of the peak of the neutrino energy flux spectrum, both
depending on the strength of the LIV. Thus, observations of the UHE neutrino
spectrum provide a clear test for the existence and amount of LIV at the
highest energies. We further discuss the ability of current and future proposed
detectors make such observations.Comment: final version to appear in Astroparticle Physic
Testing Lorentz Symmetry using High Energy Astrophysics Observations
We discuss some of the tests of Lorentz symmetry made possible by
astrophysical observations of ultrahigh energy cosmic rays, gamma-rays, and
neutrinos. These are among the most sensitive tests of Lorentz symmetry
violation because they are the highest energy phenomena known to man.Comment: revised to match the published paper. Three new references added.
arXiv admin note: substantial text overlap with arXiv:1705.08485,
arXiv:1411.588
Tests of Lorentz Invariance Using High Energy Astrophysics Observations
High-energy astrophysics observations provide the best possibilities to
detect a very small violation of Lorentz invariance, such as may be related to
the structure of space-time near the Planck scale. I discuss the possible
signatures of Lorentz invariance violation that can be manifested by observing
the spectra, polarization, and timing of gamma-rays from active galactic nuclei
and gamma-ray bursts. Other sensitive tests are provided by observations of the
spectra of ultrahigh-energy cosmic rays and very high-energy neutrinos. I also
discuss a new time-of-flight analysis of observations of GRB 090510 by the
Fermi gamma-ray Space Telescope. These results, based on high-energy
astrophysical observations, have fundamental implications for space-time
physics and quantum gravity models.Comment: Plenary Talk, Proceedngs of the Sixth Meeting on CPT and Lorentz
Symmetry (CPT'13
Neutrino telescopes under the ocean: The case for ANTARES
Neutrino telescopes offer an alternative way to explore the Universe. Several
projects are in operation or under construction. A detector under the ocean is
very promising because of the very accurate angular resolution that it
provides. The ANTARES project is intended to demonstrate the feasibilty of such
a detector.Comment: Talk given at the Neutrino98 conference, Takayama, Japan, June 4-9,
199
Constraining Superluminal Electron and Neutrino Velocities using the 2010 Crab Nebula Flare and the IceCube PeV Neutrino Events
The observation of two PeV-scale neutrino events reported by Ice Cube can, in
principle, allows one to place constraints on Lorentz invariance violation
(LIV) in the neutrino sector. After first arguing that at least one of the
IceCube events was of extragalactic origin, I derive an upper limit for {\it
the difference} between putative superluminal neutrino and electron velocities
of in units where , confirming that the
observed PeV neutrinos could have reached Earth from extragalactic sources. I
further derive a new constraint on the superluminal electron velocity, obtained
from the observation of synchrotron radiation in the Crab Nebula flare of
September, 2010. The inference that the 1 GeV -rays from
synchrotron emission in the flare were produced by electrons of energy up to
PeV indicates the non-occurrence of vacuum \'{C}erenkov radiation by
these electrons. This implies a new, strong constraint on superluminal electron
velocities . It immediately follows that
one then obtains an upper limit on the superluminal neutrino velocity {\it
alone} of , many orders of magnitude
better than the time-of-flight constraint from the SN1987A neutrino burst.
However, if the electrons are {\it subluminal} the constraint on , obtained from the Crab Nebula -ray
spectrum, places a weaker constraint on superluminal neutrino velocity of
.Comment: Expanded and clarified the discussion of the case for extragalactic
origin of the observed neutrinos adding more reference
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