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Munch June 5th, 2006 |
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The exclusion of WMAP's Hubble constant by laser interferometryAuthors: Richard Lieu, Don A. GregoryComments: ApJL submitted In a recent laser interferometry experiment, the light from a specific forbidden transition was frequency compared with that from a highly stable cryogenic laser-resonator coupling for a period of $\tau \approx$ 200 days. Through a detailed analysis, we demonstrate that while the free transition source emits light to set a frequency standard, the wavelength of the other source, being rigidly fixed by the physical size of the resonator box when a prescribed number of wavecycles must fit into the box, would have caused the emitted frequency to blueshift with time if there is Hubble expansion, because the physical distance propagated by light per unit time increases with time as space expands, thereby driving the frequency upwards if the wavelength is not allowed to change. Over the duration $\tau$ of the experiment, and given that the initial frequencies of the two sources were calibrated to be the same, the frequency of the laser-resonator should have blueshifted w.r.t. that of the reference source by the fractional amount $H_0 \tau/2 \approx$ 2 $\times$ 10$^{-11}$ for $H_0 =$ 70 km s$^{-1}$ Mpc$^{-1}$. Their non-detection of a frequency shift $\delta \nu/\nu = (4.8 \pm 5.3) \times 10^{-12}$ puts to question the reality of space expansion at the rate inferred from WMAP data. The 2$\sigma$ upper limit for the Hubble constant from this precision optical bench is $\approx$ 50 km s$^{-1}$ Mpc$^{-1}$. Full-text: PostScript, PDF, or Other formatsThe Gravitino-Overproduction Problem in Inflationary UniverseAuthors: Masahiro Kawasaki, Fuminobu Takahashi, T. T. YanagidaComments: 33 pages, 7 figures Report-no: DESY06-072 We show that the gravitino-overproduction problem is prevalent among inflation models in supergravity. An inflaton field \phi generically acquires (effective) non-vanishing auxiliary field G_\phi, if the K\"ahler potential is non-minimal. The inflaton field then decays into a pair of the gravitinos. We extensively study the cosmological constraints on G_\phi for a wide range of the gravitino mass. For many inflation models we explicitly estimate G_\phi, and show that the gravitino-overproduction problem severely constrains the inflation models, unless such an interaction as K = \kappa/2 |\phi|^2 z^2 + h.c. is suppressed (here z is the field responsible for the supersymmetry breaking). We find that many of them are already excluded or on the verge of, if \kappa \sim O(1). Full-text: PostScript, PDF, or Other formats
MSSM inflationAuthors: David H. LythComments: Latex, 2 pages Flat directions of the MSSM might support inflation. Taking into account loop corrections, the proposal of hep-ph/0605035 is viable at least in the context of split supersymmetry. Alternatively a flat direction might support modular inflation. Full-text: PostScript, PDF, or Other formats
Sub-eV upper limits on neutrino masses from cosmologyAuthors: Oystein Elgaroy (ITA, Oslo), Ofer Lahav (UCL)Comments: 2 pages, 1 figure. Contribution to the proceedings from SNOW 2006, Stockholm, May 2-6, 2006 Upper limits on neutrino masses from cosmology have been reported recently to reach the impressive sub-eV level, which is competitive with future terrestrial neutrino experiments. In this brief review of the latest limits from cosmology we point out some of the caveats that should be borne in mind when interpreting the significance of these limits. Full-text: PostScript, PDF, or Other formatsWill MINOS see new physics?Authors: Noriaki Kitazawa, Hiroaki Sugiyama, Osamu YasudaComments: 6 pages, 2 figures, uses revtex4 and graphicx Report-no: KEK-TH-1090 The effect of non-standard neutrino interactions with matter at long baseline neutrino experiments is examined in a model independent way, taking into account the constraints from all the experiments. It is found that such a non-standard interaction can enhance the flavor transition probability so significantly that the ongoing experiment MINOS may see the signal of $\nu_\mu\to\nu_e$ which is much more than the prediction by the standard scenario. It is also found that the silver channel $\nu_e\to\nu_\tau$ at a neutrino factory could have a huge enhancement. Full-text: PostScript, PDF, or Other formats
Electroweak Baryogenesis in a Two-Higgs Doublet ModelAuthors: Stephan J. HuberComments: 5 pages, 2 figures. Proceedings of Moriond 2006, Electroweak Session. 11-18 March, La Thuile (Italy) Electroweak baryogenesis fails in the SM because of too small CP violation and the lack of a strong first-order phase transition. It has been shown that supersymmetric models allow for successful baryogenesis, where the Higgsinos play an important role in the transport processes that generate the asymmetry. I will demonstrate that also non-supersymmetric models can provide the observed baryon asymmetry. The top quark takes the role of the Higgsinos. Focusing on the two-Higgs doublet model, I will discuss details of the phase transition and consequences for Higgs physics and EDM searches. Full-text: PostScript, PDF, or Other formatsWeighing neutrinos in the presence of a running primordial spectral indexAuthors: Bo Feng, Jun-Qing Xia, Jun'ichi Yokoyama, Xinmin Zhang, Gong-Bo ZhaoComments: 5 pages, 3 figures Revtex4 The three-year WMAP(WMAP3), combined with other cosmological observations from galaxy clustering and Type Ia Supernova (SNIa), prefers a non-vanishing running of the primordial spectral index independent of the low CMB multipoles. Motivated by this feature we study cosmological constraint on the neutrino mass, which severely depends on what prior we adopt for the spectral shape of primordial fluctuations, taking possible running into account. As a result we find a more stringent constraint on the sum of the three neutrino masses, m_\nu < 0.76 eV (2 \sigma), compared with the case where power-law prior is adopted to the primordial spectral shape. Full-text: PostScript, PDF, or Other formatsHolographic probabilities in eternal inflationAuthors: Raphael BoussoComments: 14 pages, 3 figures. v2: reference fixed The problem of assigning probabilities to vacua is notoriously ambiguous in the global description of eternal inflation. The local point of view is preferred by holography, and it naturally picks out a simple probability measure. This requires no ambiguous choices, such as which time slices to use, or how to weight the volume occupied by a vacuum. The local viewpoint also cuts off the weight carried by exponentially large slow-roll expansion factors or lifetimes. Full-text: PostScript, PDF, or Other formatsCan sterile neutrinos be ruled out as warm dark matter candidates?Authors: Matteo Viel, Julien Lesgourgues, Martin G. Haehnelt, Sabino Matarrese, Antonio RiottoComments: 5 pages, 3 figures We present constraints on the mass of Warm Dark Matter (WDM) particles from a combined analysis of the matter power spectrum inferred from the SDSS (Sloan Digital Sky Survey) Lyman-alpha flux power spectrum at 2.2<z<4.2, cosmic microwave background data and the galaxy power spectrum. We obtain a lower limit of m_s > 10 keV (2 sigma) if the WDM consists of sterile neutrinos and m_wdm > 2 keV (2 sigma) for early decoupled thermal relics. These results significantly improve our previous estimates based on high-resolution Lyman-alpha forest data at lower redshift. Our new limits are consistent with those of Seljak et al. (2006), albeit ~ 30 % smaller. If we combine this bound with the constraint derived from X-ray flux observations in the Coma cluster periphery (Boyarsky et al.), we find that the only allowed sterile neutrino mass is ~ 10 keV (in the standard production scenario with non-resonant neutrino oscillations). Adding constraints based on X-ray fluxes from the Andromeda galaxy or the Milky Way, we find that dark matter particles cannot be sterile neutrinos, unless the latter are produced by resonant oscillations or get diluted by some large entropy release. Full-text: PostScript, PDF, or Other formats
Gravitino Dark Matter and Cosmological ConstraintsAuthors: Frank Daniel SteffenComments: 62 pages, 20 figures Report-no: MPP-2006-66 The gravitino is a promising candidate for cold dark matter. We study cosmological constraints on scenarios in which the gravitino is the lightest supersymmetric particle and a charged slepton the next-to-lightest supersymmetric particle (NLSP). We obtain new results for the hadronic nucleosynthesis bounds by computing the 4-body decay of the NLSP slepton into the gravitino, the associated lepton, and a quark-antiquark pair. The bounds from the observed dark matter density are refined by taking into account gravitinos from both late NLSP decays and thermal scattering in the early Universe. We examine the present free-streaming velocity of gravitino dark matter and the limits from observations and simulations of cosmic structures. Assuming that the NLSP sleptons freeze out with a thermal abundance before their decay, we derive new bounds on the slepton and gravitino masses. The implications of the constraints for cosmology and collider phenomenology are discussed and the potential insights from future experiments are outlined. We propose a set of benchmark scenarios with gravitino dark matter and long-lived charged NLSP sleptons and describe prospects for the Large Hadron Collider and the International Linear Collider. Full-text: PostScript, PDF, or Other formats
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