Status report of the ANTARES project

The ANTARES project aims at the construction of an underwater neutrino telescope at the scale of 0.1 km^2 2400 m deep in the Mediterranean Sea. After a 4-year R&D program, the ANTARES project has entered the construction phase which will be concluded by the end of 2004. The current status of the project is reported.Comment: 3 pages, 2 figures. to appear in Proc. of TAUP2001 conference, Laboratori Nazionali del Gran Sasso, Sept. 200

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 Relativity at High Energies Using Spaceborne Detectors

(ABRIDGED) The Gamma-ray Large Area Space Telescope (GLAST) will measure the spectra of distant extragalactic sources of high energy gamma-rays. GLAST can look for energy dependent propagation effects from such sources as a signal of Lorentz invariance violation (LIV). Such sources should also exhibit high energy spectral cutoffs from pair production interactions with low energy photons. The properties of such cutoffs can also be used to test LIV. Detectors to measure gamma-ray polarization can look for the depolarizing effect of space-time birefingence predicted by loop quantum gravity. A spaceborne detector array looking down on Earth to study extensive air showers produced by ultrahigh energy cosmic rays can study their spectral properties and look for a possible deviation from the predicted GZK effect as another signal of LIV.Comment: 14 pages, Text of invitated talk presented at the "From Quantum to Cosmos: Fundamental Physics Studies from Space" meeting. More references adde

High energy neutrino absorption and its effects on stars in close X-ray binaries

The physics and astrophysics of high energy neutrino production and interactions in close X-ray binary systems are studied. These studies were stimulated by recent observations of ultrahigh energy gamma-rays and possibly other ultrahigh energy particles coming from the directions of Cygnus X-3 and other binary systems and possessing the periodicity characteristics of these systems. Systems in which a compact object, such as a neutron star, is a strong source of high energy particles which, in turn, produce photons, neutronos and other secondary particles by interactions in the atmosphere of the companion star were considered. The highest energy neutrinos are absorbed deep in the companion and the associated energy deposition may be large enough to effect its structure or lead to its ultimate disruption. This neutrino heating was evaluated, starting with a detailed numerical calculation of the hadronic cascade induced in the atmosphere of the companion star. For some theoretical models, the resulting energy deposition from neutrino absorption may be so great as to disrupt the companion star over an astronomically small timescale of the order of 10,000 years. Even if the energy deposition is smaller, it may still be high enough to alter the system substantially, perhaps leading to quenching of high energy signals from the source. Given the cosmic ray luminosities required to produce the observed gamma rays from cygnus X-3 and LMX X-4, such a situation may occur in these sources

Corrected Table for the Parametric Coefficients for the Optical Depth of the Universe to Gamma-rays at Various Redshifts

Table 1 in our paper, ApJ 648, 774 (2006) entitled "Intergalactic Photon Spectra from the Far IR to the UV Lyman Limit for 0 < z < 6 and the Optical Depth of the Universe to High Energy Gamma-Rays" had erroneous numbers for the coefficients fitting the parametric form for the optical depth of the universe to gamma-rays. The correct values for these parameters as described in the original text are given here in a corrected table for various redshifts for the baseline model (upper row) and fast evolution (lower row) for each individual redshift. The parametric approximation is good for optical depths between 0.01 and 100 and for gamma-ray energies up to ~2 TeV for all redshifts but also for energies up to ~10 TeV for redshifts less than 1.Comment: Table 1 corrected and new gamma-ray energy range of validity give

Intergalactic Photon Spectra from the Far IR to the UV Lyman Limit for 0<z<60 < z < 6 and the Optical Depth of the Universe to High Energy Gamma-Rays

We calculate the intergalactic photon density as a function of both energy and redshift for 0 < z < 6 for photon energies from .003 eV to the Lyman limit cutoff at 13.6 eV in a Lambda-CDM universe with $\Omega_{\Lambda} = 0.7$ and $\Omega_{m} = 0.3$. Our galaxy evolution model gives results which are consistent with Spitzer deep number counts and the spectral energy distribution of the extragalactic background radiation. We use our photon density results to extend previous work on the absorption of high energy gamma-rays in intergalactic space owing to interactions with low energy photons and the 2.7 K cosmic background radiation. We calculate the optical depth of the universe, tau, for gamma-rays having energies from 4 GeV to 100 TeV emitted by sources at redshifts from ~0 to 5. We also give an analytic fit with numerical coefficients for approximating $\tau(E_{\gamma}, z)$. As an example of the application of our results, we calculate the absorbed spectrum of the blazar PKS 2155-304 at z = 0.117 and compare it with the spectrum observed by the H.E.S.S. air Cherenkov gamma-ray telescope array.Comment: final version to be published in Ap