Lorentz Invariance Violation and the Observed Spectrum of Ultrahigh Energy Cosmic Rays

There has been much interest in possible violations of Lorentz invariance, particularly motivated by quantum gravity theories. It has been suggested that a small amount of Lorentz invariance violation (LIV) could turn off photomeson interactions of ultrahigh energy cosmic rays (UHECRs) with photons of the cosmic background radiation and thereby eliminate the resulting sharp steepening in the spectrum of the highest energy CRs predicted by Greisen Zatsepin and Kuzmin (GZK). Recent measurements of the UHECR spectrum reported by the HiRes and Auger collaborations, however, indicate the presence of the GZK effect. We present the results of a detailed calculation of the modification of the UHECR spectrum caused by LIV using the formalism of Coleman and Glashow. We then compare these results with the experimental UHECR data from Auger and HiRes. Based on these data, we find a best fit amount of LIV of $4.5^{+1.5}_{-4.5} \times 10^{-23}$,consistent with an upper limit of $6 \times 10^{-23}$. This possible amount of LIV can lead to a recovery of the cosmic ray spectrum at higher energies than presently observed. Such an LIV recovery effect can be tested observationally using future detectors.Comment: corrected proof version to be published in Astroparticle Physic

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

Collapsible reflector Patent

Self erecting parabolic reflector design for use in spac

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

Cavity-mediated long-range interaction for fast multiqubit quantum logic operations

Interactions among qubits are essential for performing two-qubit quantum logic operations. However, nature gives us only nearest neighbor interactions in simple and controllable settings. Here we propose a strategy to induce interactions among two atomic entities that are not necessarily neighbors of each other through their common coupling with a cavity field. This facilitates fast multiqubit quantum logic operations through a set of two-qubit operations. The ideas presented here are applicable to various quantum computing proposals for atom based qubits such as, trapped ions, atoms trapped in optical cavities and optical lattices.Comment: 10 pages, 3 figure

A Bootstrapping Approach for Generating Maximally Path-Entangled Photon States

We propose a bootstrapping approach to generation of maximally path-entangled states of photons, so called ``NOON states''. Strong atom-light interaction of cavity QED can be employed to generate NOON states with about 100 photons; which can then be used to boost the existing experimental Kerr nonlinearities based on quantum coherence effects to facilitate NOON generation with arbitrarily large number of photons all within the current experimental state of the art technology. We also offer an alternative scheme that uses an atom-cavity dispersive interaction to obtain sufficiently high Kerr-nonlinearity necessary for arbitrary NOON generation

Interacting double dark resonances in a hot atomic vapor of helium

We experimentally and theoretically study two different tripod configurations using metastable helium ($^4$He*), with the probe field polarization perpendicular and parallel to the quantization axis, defined by an applied weak magnetic field. In the first case, the two dark resonances interact incoherently and merge together into a single EIT peak with increasing coupling power. In the second case, we observe destructive interference between the two dark resonances inducing an extra absorption peak at the line center.Comment: 7 pages, 7 figure

A Simple Analytic Treatment of the Intergalactic Absorption Effect in Blazar Gamma-ray Spectra

We derive a new and user friendly simple analytic approximation for determining the effect of intergalactic absorption in the energy range 0.2-2 TeV and the redshift range 0.05-0.4. In these ranges, the form of the absorption coeeficient is approximately logarithmic in energy. The effect of this energy dependence is to steepen intrinsic source spectra such that a source with an approximate power-law intrinsic spectrum in this energy range with spectral index $\Gamma_{s}$ is steepened to a power-law with an observed spectral index $\Gamma_{o} =$\Gamma_{s} + $\Delta \Gamma (z)$ where $\Delta \Gamma (z)$ is a linear function of z in the redshift range 0.05-0.4. We apply this approximation to the spectra of seven TeV blazars.Comment: 9 pages, 2 eps figs., published versio