2004 (IPP)

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20122

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Author: search.filters.author.Garousi, M. R.Subject: search.filters.subject.Cosmology

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    Generation of electromagnetic fields in string cosmology with a massive scalar field on the anti D-brane
    (2012-07-06) Garousi, M. R.; Sami, M.; Tsujikawa, Shinji
    We study the generation of electromagnetic fields in a string-inspired scenario associated with a rolling massive scalar field φ on the anti-D3 branes of KKLT de Sitter vacua. The 4-dimensional DBI type effective action naturally gives rise to the coupling between the gauge fields and the inflaton φ, which leads to the production of cosmological magnetic fields during inflation due to the breaking of conformal invariance. We find that the amplitude of magnetic fields at decoupling epoch can be larger than the limiting seed value required for the galactic dynamo. We also discuss the mechanism of reheating in our scenario and show that gauge fields are sufficiently enhanced for the modes deep inside the Hubble radius with an energy density greater than that of the inflaton.
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    Cosmology from rolling massive scalar field on the anti-D3 Brane of de Sitter Vacua
    (2012-07-06) Garousi, M. R.; Sami, M.; Tsujikawa, Shinji
    We investigate a string-inspired scenario associated with a rolling massive scalar field on D-branes and discuss its cosmological implications. In particular, we discuss cosmological evolution of the massive scalar field on the ant-D3 brane of KKLT vacua. Unlike the case of tachyon field, because of the warp factor of the anti-D3 brane, it is possible to obtain the required level of the amplitude of density perturbations. We study the spectra of scalar and tensor perturbations generated during the rolling scalar inflation and show that our scenario satisfies the observational constraint coming from the Cosmic Microwave Background anisotropies and other observational data. We also implement the negative cosmological constant arising from the stabilization of the modulus fields in the KKLT vacua and find that this leads to a successful reheating in which the energy density of the scalar field effectively scales as a pressureless dust. The present dark energy can be also explained in our scenario provided that the potential energy of the massive rolling scalar does not exactly cancel with the amplitude of the negative cosmological constant at the potential minimum.