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 ÃCDM universe with à ¼ 0:7 and m ¼ 0:3. The basic features of our backward-evolution model for galaxies were developed in earlier papers by Malkan & Stecker.With a few improvements, we find that this evolutionary model gives predictions of new deep number counts from Spitzer, as well as a calculation of the spectral energy distribution of the diffuse infrared background, which are in good agreement with the data. We then use our calculated intergalactic photon densities to extend previous work on the absorption of high-energy -rays in intergalactic space owing to interactions with low-energy photons and the 2.7 K cosmic microwave background radiation. We calculate the optical depth of the universe, , for -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 (E ; z). As an example of the application of our results, we calculate the absorbed spectrum of the blazar PKS 2155À304 at z ¼ 0:117 and compare it with the spectrum observed by the HESS air Cerenkov -ray telescope array.

High energy cosmic neutrino observations provide a sensitive test of Lorentz invariance violation (LIV), which may be a consequence of quantum gravity theories. We consider a class of nonrenormalizable, Lorentz invariance violating operators that arise in an effective field theory (EFT) description of Lorentz invariance violation in the neutrino sector inspired by Planck-scale physics and quantum gravity models. We assume a conservative generic scenario for the redshift distribution of extragalactic neutrino sources and employ Monte Carlo techniques to describe superluminal neutrino propagation, treating kinematically allowed energy losses of superluminal neutrinos caused by both vacuum pair emission (VPE) and neutrino splitting. We consider EFTs with both nonrenormalizable CPT -odd and non-renormalizable CPT -even operator dominance. We then compare the spectra derived using our Monte Carlo calculations in both cases with the spectrum observed by IceCube in order to determine the implications of our results regarding Planck-scale physics. We find that if the drop off in the neutrino flux above ∼ 2 PeV is caused by Planck scale physics, rather than by a limiting energy in the source emission, a potentially significant pileup effect would be produced just below the drop off energy in the case of CPT -even operator dominance. However, such a clear drop off effect would not be observed if the CPT -odd, CPT -violating term dominates.

Using cosmic-ray energetics as a discriminator, we investigate the viability of evolutionary models for the light elements, Li, Be and B (LiBeB). We employ a Monte Carlo code which incorporates hitherto ignored effects, the delayed mixing into the ISM both of the synthesized Fe, due to its incorporation into high velocity dust grains, and of the cosmic-ray produced LiBeB, due to the transport of the cosmic rays. We use supernova O and Fe ejecta based on calculations and observations, and we normalize the LiBeB production to the integral energy imparted to cosmic rays per supernova. We find that models in which the cosmic rays are accelerated mainly out of the average ISM which is increasingly metal poor at early times, significantly under predict the measured Be abundance of the early Galaxy, the increase in [O/Fe] with decreasing [Fe/H] indicated by recent data notwithstanding. We suggest that this increase could be due to the delayed mixing of the Fe. On the other hand, if the cosmic-ray metals are accelerated primarily out of supernova ejecta

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