7,668 research outputs found

    Bounds on isocurvature perturbations from CMB and LSS data

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    We obtain very stringent bounds on the possible cold dark matter, baryon and neutrino isocurvature contributions to the primordial fluctuations in the Universe, using recent cosmic microwave background and large scale structure data. In particular, we include the measured temperature and polarization power spectra from WMAP and ACBAR, as well as the matter power spectrum from the 2dF galaxy redshift survey. Neglecting the possible effects of spatial curvature, tensor perturbations and reionization, we perform a Bayesian likelihood analysis with nine free parameters, and find that the amplitude of the isocurvature component cannot be larger than about 31% for the cold dark matter mode, 91% for the baryon mode, 76% for the neutrino density mode, and 60% for the neutrino velocity mode, at 2-sigma, for uncorrelated models. On the other hand, for correlated adiabatic and isocurvature components, the fraction could be slightly larger. However, the cross-correlation coefficient is strongly constrained, and maximally correlated/anticorrelated models are disfavored. This puts strong bounds on the curvaton model, independently of the bounds on non-Gaussianity.Comment: 4 pages, 1 figure, some minor corrections; version accepted in PR

    Gauge invariant MSSM inflaton

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    We argue that all the necessary ingredients for successful inflation are present in the flat directions of the Minimally Supersymmetric Standard Model. We show that out of many gauge invariant combinations of squarks, sleptons and Higgses, there are two directions, LLe{\bf LLe}, and udd{\bf udd}, which are promising candidates for the inflaton. The model predicts more than 10310^3 e-foldings with an inflationary scale of HinfO(110)H_{\rm inf}\sim {\cal O}(1-10) GeV, provides a tilted spectrum with an amplitude of δH105\delta_H\sim 10^{-5} and a negligible tensor perturbation. The temperature of the thermalized plasma could be as low as TrhO(110)T_{rh}\sim {\cal O}(1-10)~TeV. Parts of the inflaton potential can be determined independently of cosmology by future particle physics experiments.Comment: 4 revtex pages, some references added, stabilization of moduli and supergravity effects are discusse

    Uncertainties of predictions in models of eternal inflation

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    In a previous paper \cite{MakingPredictions}, a method of comparing the volumes of thermalized regions in eternally inflating universe was introduced. In this paper, we investigate the dependence of the results obtained through that method on the choice of the time variable and factor ordering in the diffusion equation that describes the evolution of eternally inflating universes. It is shown, both analytically and numerically, that the variation of the results due to factor ordering ambiguity inherent in the model is of the same order as their variation due to the choice of the time variable. Therefore, the results are, within their accuracy, free of the spurious dependence on the time parametrization.Comment: 30 pages, RevTeX, figure included, added some references and Comments on recent proposal (gr-qc/9511058) of alternative regularization schemes, to appear in Phys. Rev.

    Unambiguous probabilities in an eternally inflating universe

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    ``Constants of Nature'' and cosmological parameters may in fact be variables related to some slowly-varying fields. In models of eternal inflation, such fields will take different values in different parts of the universe. Here I show how one can assign probabilities to values of the ``constants'' measured by a typical observer. This method does not suffer from ambiguities previously discussed in the literature.Comment: 7 pages, Final version (minor changes), to appear in Phys. Rev. Let

    Cell interactions in the control of size in Drosophila wings.

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    Lambda-inflation and CMB anisotropy

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    We explore a broad class of three-parameter inflationary models, called the Λ\Lambda-inflation, and its observational predictions: high abundance of cosmic gravitational waves consistent with the Harrison-Zel'dovich spectrum of primordial cosmological perturbations, the non-power-law wing-like spectrum of matter density perturbations, high efficiency of these models to meet current observational tests, and others. We show that a parity contribution of the gravitational waves and adiabatic density perturbations into the large-scale temperature anisotropy, T/S 1\sim 1, is a common feature of Λ\Lambda-inflation; the maximum values of T/S (basically not larger than 10) are reached in models where (i) the local spectrum shape of density perturbations is flat or slightly red (nS<1n_S{}_\sim^< 1), and (ii) the residual potential energy of the inflaton is near the GUT scale (V01/41016GeVV_0^{{1/4}} \sim 10^{16} GeV). The conditions to find large T/S in the paradigm of cosmic inflation and the relationship of T/S to the ratio of the power spectra, rr, and to the inflationary γ\gamma and Hubble parameters, are discussed. We argue that a simple estimate, T/S3r12γ(H6×1013GeV)2\simeq 3r\simeq 12\gamma \simeq (\frac{H}{6\times 10^{13}{\rm GeV}})^2, is true for most known inflationary solutions and allows to relate straightforwardly the important parameters of observational and physical cosmology.Comment: 29 pages, 3 figures include
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