15 research outputs found

    Leptogenesis from Gravity Waves in Models of Inflation

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    We present a new mechanism for creating the observed cosmic matter-antimatter asymmetry which satisfies all three Sakharov conditions from one common thread, gravitational waves. We generate lepton number through the gravitational anomaly in the lepton number current. The source term comes from elliptically polarizated gravity waves that are produced during inflation if the inflaton field contains a CP-odd component. In simple inflationary scenarios, the generated matter asymmetry is very small. We describe some special conditions in which our mechanism can give a matter asymmetry of realistic size.Comment: 4 pages, RevTeX4.1 format; an error in computations correcte

    Can the string scale be related to the cosmic baryon asymmetry?

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    In a previous work, a mechanism was presented by which baryon asymmetry can be generated during inflation from elliptically polarized gravitons. Nonetheless, the mechanism only generated a realistic baryon asymmetry under special circumstances which requires an enhancement of the lepton number from an unspecified GUT. In this note we provide a stringy embedding of this mechanism through the Green-Schwarz mechanism, demonstrating that if the model-independent axion is the source of the gravitational waves responsible for the lepton asymmetry, one can observationally constrain the string scale and coupling.Comment: 12 Pages, typo corrected in the tex

    Brane Gas Cosmology, M-theory and Little String Theory

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    We generalize the Brane Gas Cosmological Scenario to M-theory degrees of freedom, namely M5M5 and M2M2 branes. Without brane intersections, the Brandenberger Vafa(BV) arguments applied to M-theory degrees of freedom generically predict a large 6 dimensional spacetime. We show that intersections of M5M5 and M2M2 branes can instead lead to a large 4 dimensional spacetime. One dimensional intersections in 11D is related to (2,0) little strings (LST) on NS5 branes in type IIA. The gas regime of membranes in M-theory corresponds to the thermodynamics of LST obtained from holography. We propose a mechanism whereby LST living on the worldvolume of NS5 (M5)-branes wrapping a five dimensional torus, annihilate most efficiently in 3+1 dimensions leading to a large 3+1 dimensional spacetime. We also show that this picture is consistent with the gas approximation in M-theory.Comment: 8 page

    A thermal instability for positive brane cosmological constant in the Randall-Sundrum cosmologies

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    We describe a novel dynamical mechanism to radiate away a positive four dimensional cosmological constant, in the Randall-Sundrum cosmological scenario. We show that there are modes of the bulk gravitational field for which the brane is effectively a mirror. This will generally give rise to an emission of thermal radiation from the brane into the bulk. The temperature turns out to be nonvanishing only if the effective four dimensional cosmological constant is positive. In any theory where the four dimensional vacuum energy is a function of physical degrees of freedom, there is then a mechanism that radiates away any positive four dimensional cosmological constant.Comment: 14 pages. The discussion on the relation between temperature and effective 4d cosmological constant is changed. References are adde
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