Munch

We present a comprehensive study of TeV black hole events in Earth's atmosphere originated by cosmic rays of very high energy. An advanced fortran Monte Carlo code is developed and used to simulate black hole extensive air showers from ultrahigh-energy neutrino-nucleon interactions. We investigate the characteristics of these events, compare the black hole air showers to standard model air showers, and test different theoretical and phenomenological models of black hole formation and evolution. The main features of black hole air showers are found to be independent of the model considered. No significant differences between models are likely to be observed at fluorescence telescopes and/or ground arrays. We also discuss the tau ``double bang'' signature in black hole air showers. We find that the energy deposited in the second bang is too small to produce a detectable peak. Our results show that the theory of TeV-scale black holes in ultrahigh-energy cosmic rays leads to robust predictions, but the fine prints of new physics are hardly to be investigated through atmospheric black hole events in the near future.

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Discussion of EGRET Excess

EGRET Excess of Diffuse Galactic Gamma Rays as Tracer of Dark Matter

Authors: W. de Boer, C. Sander, V. Zhukov (Univ. Karlsruhe) A.V. Gladyshev, D.I. Kazakov (JINR, Dubna)
Comments: 29 pages, 15 figures, accepted by A&A

The public data from the EGRET space telescope on diffuse Galactic gamma rays in the energy range from 0.1 to 10 GeV are reanalyzed with the purpose of searching for signals of Dark Matter annihilation (DMA). The analysis confirms the previously observed excess for energies above 1 GeV in comparison with the expectations from conventional Galactic models. In addition, the excess was found to show all the key features of a signal from Dark Matter Annihilation (DMA): a) the excess is observable in all sky directions and has the same shape everywhere, thus pointing to a common source; b) the shape corresponds to the expected spectrum of the annihilation of non-relativistic massive particles into - among others - neutral $\pi^0$ mesons, which decay into photons. From the energy spectrum of the excess we deduce a WIMP mass between 50 and 100 GeV, while from the intensity of the excess in all sky directions the shape of the halo could be reconstructed. The DM halo is consistent with an almost spherical isothermal profile with substructure in the Galactic plane in the form of toroidal rings at 4 and 14 kpc from the center. These rings lead to a peculiar shape of the rotation curve, in agreement with the data, which proves that the EGRET excess traces the Dark Matter.

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Diffuse Galactic continuum gamma rays. A model compatible with EGRET data and cosmic-ray measurements

Authors: A. W. Strong (MPE, Garching), I. V. Moskalenko (NASA/GSFC), O. Reimer (Bochum)
Comments: To be published in The Astrophysical Journal v.613, 1 Oct. 2004 issue; 16 pages, 60 ps-figures, 4 tables emulateapj.sty, natbib.sty, aastex.cls
Journal-ref: Astrophys.J. 613 (2004) 962-976

We present a study of the compatibility of some current models of the diffuse Galactic continuum gamma rays with EGRET data. A set of regions sampling the whole sky is chosen to provide a comprehensive range of tests. The range of EGRET data used is extended to 100 GeV. The models are computed with our GALPROP cosmic-ray propagation and gamma-ray production code. We confirm that the "conventional model" based on the locally observed electron and nucleon spectra is inadequate, for all sky regions. A conventional model plus hard sources in the inner Galaxy is also inadequate, since this cannot explain the GeV excess away from the Galactic plane. Models with a hard electron injection spectrum are inconsistent with the local spectrum even considering the expected fluctuations; they are also inconsistent with the EGRET data above 10 GeV.
We present a new model which fits the spectrum in all sky regions adequately. Secondary antiproton data were used to fix the Galactic average proton spectrum, while the electron spectrum is adjusted using the spectrum of diffuse emission itself. The derived electron and proton spectra are compatible with those measured locally considering fluctuations due to energy losses, propagation, or possibly details of Galactic structure. This model requires a much less dramatic variation in the electron spectrum than models with a hard electron injection spectrum, and moreover it fits the gamma-ray spectrum better and to the highest EGRET energies. It gives a good representation of the latitude distribution of the gamma-ray emission from the plane to the poles, and of the longitude distribution. We show that secondary positrons and electrons make an essential contribution to Galactic diffuse gamma-ray emission.

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The supersymmetric interpretation of the EGRET excess of diffuse Galactic gamma rays

Authors: W. de Boer (1), C. Sander (1), V. Zhukov (1), A.V. Gladyshev (2), D.I. Kazakov (2) ((1) Univ. Karlsruhe (2) JINR (Dubna))
Comments: 9 pages, 5 figures, subm. to Phys. Letters

Recently it was shown that the excess of diffuse Galactic gamma rays above 1 GeV traces the Dark Matter halo, as proven by reconstructing the peculiar shape of the rotation curve of our Galaxy from the gamma ray excess. This can be interpreted as a Dark Matter annihilation signal. In this paper we investigate if this interpretation is consistent with Supersymmetry. It is found that the EGRET excess combined with all electroweak constraints is fully consistent with the minimal mSUGRA model for scalars in the TeV range and gauginos below 500 GeV.

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High Energy Neutrinos from Cosmic Ray Interactions in Clusters of Galaxies

Authors: Daniel De Marco, Pasquale Blasi, Patricia Hansen, Todor Stanev
Comments: 10 pages, 10 figures, submitted to PRD

The spatial clustering of galaxies in galaxy clusters implies that the background of infrared (IR) light in the intracluster medium (ICM) may exceed the universal background. Cosmic rays injected within the ICM propagate diffusively and at low enough energies are trapped there for cosmological times. The photopion production interactions of cosmic rays with the IR photons are responsible for the generation of neutrinos whose detection may shed some light on the origin and propagation of high energy cosmic rays in the universe. Here we discuss our calculations of the flux of neutrinos from single clusters as well as the contribution of photopion production in clusters of galaxies to the diffuse neutrino background.

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Cosmological Neutrinos

Is cosmology compatible with sterile neutrinos?

Authors: Scott Dodelson, Alessandro Melchiorri, Anze Slosar
Comments: 5 pages, 3 figures

By combining data from cosmic microwave background (CMB) experiments (including the recent BOOMERANG-2K2 results), large scale structure (LSS) and Lyman-$\alpha$ forest observations, we constrain the hypothesis of a fourth, sterile, massive neutrino. For the 3 massless + 1 massive neutrino case we bound the mass of the sterile neutrino to m_s<0.55eV at 95% c.l.. These results exclude at high significance the sterile neutrino hypothesis as an explanation of the LSND anomaly. We then generalize the analysis to account for active neutrino masses (which tightens the limit to m_{s}<0.51eV) and the possibility that the sterile abundance is not thermal. In the latter case, the contraints in the (mass, density) plane are non-trivial. For a mass of >1eV or <0.05eV the cosmological energy density in sterile neutrinos is always constrained to be \omega_nu<0.005 at 9% c.l.. However, for a sterile neutrino mass of ~0.25eV, omega_nu can be as large as 0.015.

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Cosmological Signatures of Interacting Neutrinos

Authors: Nicole F. Bell (Caltech), Elena Pierpaoli (Caltech), Kris Sigurdson (Caltech and IAS)
Comments: 16 pages, 14 figures, submitted to Phys. Rev. D
Report-no: KRL-MAP-309

We investigate signatures of neutrino scattering in the Cosmic Microwave Background (CMB) and matter power spectra, and the extent to which present cosmological data can distinguish between a free streaming or tightly coupled fluid of neutrinos. If neutrinos have strong non-standard interactions, for example, through the coupling of neutrinos to a light boson, they may be kept in equilibrium until late times. We show how the power spectra for these models differ from more conventional neutrino scenarios, and use CMB and large scale structure data to constrain these models. CMB polarization data improves the constraints on the number of massless neutrinos, while the Lyman-alpha power spectrum improves the limits on the neutrino mass. Neutrino mass limits depend strongly on whether some or all of the neutrino species interact and annihilate. The present data can accommodate a number of tightly-coupled relativistic degrees of freedom, and none of the interacting-neutrino scenarios considered are ruled out by current data -- although Age considerations disfavor a model with three annihilating neutrinos with very large neutrino masses.

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An excursion set model of the cosmic web: The abundance of sheets, filaments and halos

Authors: Jiajian Shen, Tom Abel, Houjun Mo, Ravi Sheth
Comments: 20 pages, 7 figures, submitted to ApJ

We discuss an analytic approach for modeling structure formation in sheets, filaments and knots. This is accomplished by combining models of triaxial collapse with the excursion set approach: sheets are defined as objects which have collapsed along only one axis, filaments have collapsed along two axes, and halos are objects in which triaxial collapse is complete. In the simplest version of this approach, which we develop here, large scale structure shows a clear hierarchy of morphologies: the mass in large-scale sheets is partitioned up among lower mass filaments, which themselves are made-up of still lower mass halos. Our approach provides analytic estimates of the mass fraction in sheets, filaments and halos, and its evolution, for any background cosmological model and any initial fluctuation spectrum. In the currently popular $\Lambda$CDM model, our analysis suggests that more than 99% of the mass in sheets, and 72% of the mass in filaments, is stored in objects more massive than $10^{10} M_{\odot}$ at the present time. For halos, this number is only 46%. Our approach also provides analytic estimates of how halo abundances at any given time correlate with the morphology of the surrounding large-scale structure, and how halo evolution correlates with the morphology of large scale structure.

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Measurement of the Spatial Cross-Correlation Function of Damped Lyman Alpha Systems and Lyman Break Galaxies

Authors: J. Cooke (1), A. M. Wolfe (1), E. Gawiser (2), J. X. Prochaska (3), ((1) UC San Diego, (2) Yale University, (3) UC Santa Cruz/UCO-Lick Observatory)
Comments: 12 pages, 2 figures, accepted for publication in Astrophysical Journal Letters

We present the first spectroscopic measurement of the spatial cross-correlation function between damped Lyman alpha systems (DLAs) and Lyman break galaxies (LBGs). We obtained deep u'BVRI images of nine QSO fields with 11 known z ~ 3 DLAs and spectroscopically confirmed 211 R < 25.5 photometrically selected z > 2 LBGs. We find strong evidence for an overdensity of LBGs near DLAs versus random, the results of which are similar to that of LBGs near other LBGs. A maximum likelihood cross-correlation analysis found the best fit correlation length value of r_0 = 2.9^(+1.4)_(-1.5) h^(-1)Mpc using a fixed value of gamma = 1.6. The implications of the DLA-LBG clustering amplitude on the average dark matter halo mass of DLAs are discussed.

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Can Inflation solve the Hierarchy Problem?

Authors: Tirthabir Biswas, Alessio Notari
Comments: 7 pages

Inflation with tunneling from a false to a true vacuum becomes viable in the presence of a scalar field that slows down the initial de Sitter phase. As a by-product this field also sets dynamically the value of the Newton constant observed today. This can be very large if the tunneling rate (which is exponentially sensitive to the barrier) is small enough. Therefore along with Inflation we also provide a natural dynamical explanation for why gravity is so weak today. Moreover we predict a spectrum of gravity waves peaked at around 0.1 mHz, that will be detectable by the planned space inteferometer LISA.

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Producing a Scale-Invariant Spectrum of Perturbations in a Hagedorn Phase of String Cosmology

Authors: Ali Nayeri, Robert H. Brandenberger, Cumrun Vafa
Comments: 4 pages, 1 figure
Report-no: HUTP-05/A048

We study the generation of cosmological perturbations during the Hagedorn phase of string gas cosmology. Using tools of string thermodynamics we provide indications that it may be possible to obtain a nearly scale-invariant spectrum of cosmological fluctuations on scales which are of cosmological interest today. In our cosmological scenario, the early Hagedorn phase of string gas cosmology goes over smoothly into the radiation-dominated phase of standard cosmology, without having a period of cosmological inflation.

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