Munch

We consider the ultra-high energy cosmic ray (UHECR) spectrum as measured by the Pierre Auger Observatory. Top-down models for the origin of UHECRs predict an increasing photon component at energies above about $10^{19.7}$eV. Here we present a simple prescription to compare the Auger data with a prediction assuming a pure proton component or a prediction assuming a changing primary component appropriate for a top-down model. We find that the UHECR spectrum predicted in top-down models is a good fit to the Auger data. Eventually, Auger will measure a composition-independent spectrum and will be capable of either confirming or excluding the quantity of photons predicted in top-down models.

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Neutralino with the Right Cold Dark Matter Abundance in (Almost) Any Supersymmetric Model

Authors: Graciela B. Gelmini, Paolo Gondolo
Comments: 4 pages, 1 figure
Report-no: UCLA/06/TEP/07

We consider non-standard cosmological models in which the late decay of a scalar field $\phi$ reheats the Universe to a low reheating temperature, between 5 MeV and the standard freeze-out temperature of neutralinos of mass $m_{\chi}$. We point out that in these models all neutralinos with standard density $\Omega_{\rm std} \gtrsim 10^{-5} (100 {\rm GeV}/m_\chi)$ can have the density of cold dark matter, provided the right combination of the following two parameters can be achieved in the high energy theory: the reheating temperature, and the ratio of the number of neutralinos produced per $\phi$ decay over the $\phi$ field mass. We present the ranges of these parameters where a combination of thermal and non-thermal neutralino production leads to the desired density, as functions of $\Omega_{\rm std}$ and $m_{\chi}$.

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Measuring neutrino masses and dark energy with weak lensing tomography

Authors: Steen Hannestad, Huitzu Tu, Yvonne Y. Y. Wong
Comments: 21 pages, 4 figures, uses iopart.cls
Report-no: MPP-2006-15

Surveys of weak gravitational lensing of distant galaxies will be one of the key cosmological probes in the future. We study the ability of such surveys to constrain neutrino masses and the equation of state parameter of the dark energy, focussing on how tomographic information can improve the sensitivity to these parameters. We also provide a detailed discussion of systematic effects pertinent to weak lensing surveys, and the possible degradation of sensitivity to cosmological parameters due to these effects. For future probes such as the Large Synoptic Survey Telescope survey, we find that, when combined with cosmic microwave background data from the Planck satellite, a sensitivity to neutrino masses of sigma(sum m_nu) < 0.05 eV can be reached. This results is robust against variations in the running of the scalar spectral index, the time-dependence of dark energy equation of state, and/or the number of relativistic degrees of freedom.

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A new bound on the neutrino mass from the SDSS baryon acoustic peak

Authors: Ariel Goobar, Steen Hannestad, Edvard Mortsell, Huitzu Tu
Comments: 12 pages, 3 figures, JCAP format

We have studied bounds on the neutrino mass using new data from the Sloan Digital Sky Survey measurement of the baryon acoustic peak. We find that even in models with a running spectral index where the number of neutrinos and the dark energy equation of state are allowed to vary, the bound on the sum of neutrino masses is robustly below 0.5 eV. Using the SDSS Lyman-alpha constraint on the amplitude of the matter power spectrum at small scales pushes the bound to \sum m_nu < 0.30 eV (95% C.L.).

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CMB Polarization due to Scattering in Clusters

Authors: M. Shimon, Y. Rephaeli, B. W. O'Shea, M. L. Norman
Comments: 8 pages, 9 figures. accepted for publication in MNRAS

Scattering of the cosmic microwave background (CMB) in clusters of galaxies polarizes the radiation. We explore several polarization components which have their origin in the kinematic quadrupole moments induced by the motion of the scattering electrons, either directed or random. Polarization levels and patterns are determined in a cluster simulated by the hydrodynamical Enzo code. We find that polarization signals can be as high as $\sim 1 \mu$K, a level that may be detectable by upcoming CMB experiments.

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Tracing early structure formation with massive starburst galaxies and their implications for reionization

Authors: Kentaro Nagamine (UCSD), Renyue Cen (Princeton), Steven R. Furlanetto (Caltech), Lars Hernquist (Harvard), Christopher Night (Harvard), Jeremiah P. Ostriker (Princeton)
Comments: 9 pages, 4 figures. Summary of the talk given at the "First Light & Reionization" workshop at UC Irvine, May 2005. The published article is available from this http URL
Journal-ref: New Astron.Rev. 50 (2006) 29-34
DOI: 10.1016/j.newar.2005.11.002

Cosmological hydrodynamic simulations have significantly improved over the past several years, and we have already shown that the observed properties of Lyman-break galaxies (LBGs) at z=3 can be explained well by the massive galaxies in the simulations. Here we extend our study to z=6 and show that we obtain good agreement for the LBGs at the bright-end of the luminosity function (LF). Our simulations also suggest that the cosmic star formation rate density has a peak at z= 5-6, and that the current LBG surveys at z=6 are missing a significant number of faint galaxies that are dimmer than the current magnitude limit. Together, our results suggest that the universe could be reionized at z=6 by the Pop II stars in ordinary galaxies. We also estimate the LF of Lyman-alpha emitters (LAEs) at z=6 by relating the star formation rate in the simulation to the Ly-alpha luminosity. We find that the simulated LAE LFs agree with the observed data provided that the net escape fraction of Ly-alpha photon is f_{Ly-alpha} <= 0.1. We investigate two possible scenarios for this effect: (1) all sources in the simulation are uniformly dimmer by a factor of 10 through attenuation, and (2) one out of ten LAEs randomly lights up at a given moment. We show that the correlation strength of the LAE spatial distribution can possibly distinguish the two scenarios.

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The consistency equation hierarchy in single-field inflation models

Authors: Marina Cortês, Andrew R Liddle
Comments: 5 pages RevTeX

Inflationary consistency equations relate the scalar and tensor perturbations. We elucidate the infinite hierarchy of consistency equations of single-field inflation, the first of which is the well-known relation A_T^2/A_S^2 = -n_T/2 between the amplitudes and the tensor spectral index. We write a general expression for all consistency equations both to first and second-order in the slow-roll expansion. We discuss the relation to other consistency equations that have appeared in the literature, in particular demonstrating that the approximate consistency equation recently introduced by Chung and collaborators is equivalent to the second consistency equation of Lidsey et al. (1997).

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Is the dark matter interpretation of the EGRET gamma excess compatible with antiproton measurements?

Authors: L. Bergstrom, J. Edsjo, M. Gustafsson, P. Salati
Comments: 14 pages, 5 figures

We investigate the internal consistency of the halo dark matter model which has been proposed by de Boer et al. to explain the excess of galactic gamma-ray observed by the EGRET experiment. Any model based on dark matter annihilation into quark jets, such as the supersymmetric model proposed by de Boer et al., inevitably also predicts a primary flux of antiprotons from the same jets. Since propagation of the antiprotons in the unconventional, disk-dominated type of halo model used by de Boer et al. is strongly constrained by the measured ratio of boron to carbon nuclei in cosmic rays, we investigate the viability of the model using the DarkSUSY package to compute the gamma-ray and antiproton fluxes. We are able to show that their model is excluded by a wide margin from the measured flux of antiprotons. % We therefore find that a model of the type suggested by Moskalenko et al., where the intensities of protons and electrons in the cosmic rays vary with galactic position, is far more plausible.

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Ricci Flow Gravity

Authors: Wolfgang Graf
Comments: 15 pages. V2: improved presentation, in particular Jordan vs. Brans-Dicke and on viability. Added section on physical interpretation
Subj-class: General Relativity and Quantum Cosmology; Differential Geometry

A theory of gravitation is proposed, modeled after the notion of a Ricci flow. In addition to the metric an independent volume enters as a fundamental geometric structure. Einstein gravity is included as a limiting case. Despite being a scalar-tensor theory the coupling to matter is different from Jordan-Brans-Dicke gravity. In particular there is no adjustable coupling constant. For the solar system the effects of Ricci flow gravity cannot be distinguished from Einstein gravity and therefore it passes all classical tests. However for cosmology significant deviations from standard Einstein cosmology will appear.

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Finite cosmology and a CMB cold spot

Authors: R.J. Adler, J.D. Bjorken, J.M. Overduin
Comments: 20 pages, 12 figures

The standard cosmological model posits a spatially flat universe of infinite extent. However, no observation, even in principle, could verify that the matter extends to infinity. In this work we model the universe as a finite spherical ball of dust and dark energy, and obtain a lower limit estimate of its mass and present size: the mass is at least 5 x 10^23 solar masses and the present radius is at least 50 Gly. If we are not too far from the dust-ball edge we might expect to see a cold spot in the cosmic microwave background, and there might be suppression of the low multipoles in the angular power spectrum. Thus the model may be testable, at least in principle. We also obtain and discuss the geometry exterior to the dust ball; it is Schwarzschild-de Sitter with a naked singularity, and provides an interesting picture of cosmogenesis. Finally we briefly sketch how radiation and inflation eras may be incorporated into the model.

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Phenomenological Indications of the Scale of Supersymmetry

Authors: J. Ellis, S. Heinemeyer, K.A. Olive, G. Weiglein
Comments: 45 pages, 14 figures
Report-no: CERN-PH-TH/2006-028, DCPT/06/24, IPPP/06/12, UMN-TH-2432/06, FTPI-MINN-06/05

Electroweak precision measurements can provide indirect information about the possible scale of supersymmetry already at the present level of accuracy. We update the present-day sensitivities of precision data using the new experimental top-quark mass, m_t = 172.7 \pm 2.9 GeV, within the constrained minimal supersymmetric extension of the Standard Model (CMSSM), in which there are three independent soft supersymmetry-breaking parameters m_{1/2}, m_0 and A_0. In addition to M_W and sin^2 theta_eff, the analysis is based on (g-2)_\mu, BR(b -> s gamma) and the lightest MSSM Higgs boson mass, M_h. Assuming initially that the lightest supersymmetric particle (LSP) is a neutralino, we display the CMSSM results as functions of m_{1/2}, fixing m_0 so as to obtain the cold dark matter density allowed by WMAP and other cosmological data for specific values of A_0, tan_beta and mu > 0. For a sample value of tan_beta we analyze how the global chi^2 function would change following a possible future evolution of the experimental central value of m_t and its error. In a second step, we extend the analysis to other constrained versions of the MSSM: the NUHM in which the soft supersymmetry-breaking contributions to the Higgs masses are independent and the Higgs mixing parameter mu and the pseudoscalar Higgs mass M_A become additional free parameters compared to the CMSSM, a VCMSSM in which the bilinear soft supersymmetry breaking parameter B_0 = A_0 - m_0, and the GDM in which the LSP is the gravitino. In all scenarios we find indications for relatively light soft supersymmetry-breaking masses, offering good prospects for the LHC and the ILC, and in some cases also for the Tevatron.

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Dark energy explained by the mixing of neutrinos

Authors: A.Capolupo, S.Capozziello, G.Vitiello
Comments: 4 pages

The explanation of the dark energy budget of the universe, which gives rise to the accelerated behavior of cosmic flow, might not require to search for exotic candidates (e.g. scalar particles) which, up to now, have not been detected. We propose it resides in the QFT neutrino mixing phenomenon.

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On the influence of the global cosmological expansion on the local dynamics in the Solar System

Authors: Matteo Carrera, Domenico Giulini
Comments: 37 pages, 2 figures
Report-no: Freiburg THEP-06/03

In this expository paper we address the question of whether, and to what extent, the cosmological expansion influences the dynamics on small scales (as compared to cosmological ones), particularly in our Solar System. We distinguish between dynamical and kinematical effects and critically review the status of both as presented in the current literature.

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