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

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

Search for the Footprints of New Physics with Laboratory and Cosmic Neutrinos

Observations of high energy neutrinos, both in the laboratory and from cosmic sources, can be a useful probe in searching for new physics. Such observations can provide sensitive tests of Lorentz invariance violation (LIV), which may be a the result of quantum gravity physics (QG). We review some observationally testable consequences of LIV using effective field theory (EFT) formalism. To do this, one can postulate the existence of additional small LIV terms in free particle Lagrangians, suppressed by powers of the Planck mass. The observational consequences of such terms are then examined. In particular, one can place limits on a class of non-renormalizable, mass dimension five and six Lorentz invariance violating operators that may be the result of QG.Comment: Version of a review article in Modern Physics Letters A with eq. (11) corrected post-publication. arXiv admin note: substantial text overlap with arXiv:1411.588

Can Gamma Ray Bursts Produce the Observed Cosmic Rays Above 102010^{20} eV?

It has been suggested that cosmological gamma-ray bursts (GRBs) can produce the observed flux and spectrum of cosmic rays at the highest energies. However, recent observations indicate that the redshift distribution of GRBs most likely follows that of the star formation rate in the universe, a rate which was much higher at redshifts 1.5-2 than it is today. Thus, most GRBs are at high redshifts. As a consequence, any cosmic rays emitted by these GRBs at energies above 2-3 X 10^{19} eV would be strongly attenuated by interactions with the 3K background radiation. If one assumes rough equality between the energy released in 10^{-2} to 1 MeV photons and that released in 10^{20} eV cosmic rays, then less than 10 per cent of the cosmic rays observed above 10^{20} eV can be accounted for by GRBs.Comment: 7 tex pages, no figures, one reference added to previous version, Astroparticle Physics, in pres

Gamma rays from the magellanic clouds

Predicted gamma ray fluxes from the Megallanic Clouds, obtained by using updated parameters, are significantly above the values previously determined, and well within the capabilities of observation from COS-B satellite. Concepts relating galactic gamma ray production and other Population 1 phenomena in the Milky Way were used to postulate a factor of four increase in predicted flux, based on the galactic origin hypothesis. The values obtained provide a possible test of two interpretations of gamma ray emission: enhancement in the inner galaxy from gas and cosmic ray sources alone, or increases produced by the trapping of cosmic rays in spiral arms. Because spiral structure is absent in the small cloud, and questionable in the large cloud, and both clouds are classed as irregular galaxies, the predicted enhancement in gamma ray flux may not be as great in the absence of clear spiral structure