M. Orito

Observational Constraints on Dark Radiation in Brane Cosmology

Center for Astrophysics, Department of Physics,University of Notre Dame, Notre Dame, IN 46556(Dated: February 5, 2008)We analyze the observational constraints on brane-world cosmology whereby the universe is de-scribed as a three-brane embedded in a five-dimensional anti-de Sitter space. In this brane-universecosmology, the Friedmann equation is modified by the appearance of extra terms which derive fromexistence of the extra dimensions. In the present work we concentrate on the “dark radiation”term which diminishes with cosmic scale factor as a

Constraints on Cosmic Quintessence and Quintessential Inflation

Recently, attempts have been made to understand the apparent near coincidence of the present dark energy and matter energy in terms of a dynamical attractor-like solution for the evolution of a “quintessence” scalar field. In these models the field couples with the dominant constituent and only acts like a cosmological constant after the onset of the matter dominated epoch. A generic feature of such solutions, however, is the possibility of significant energy density in the scalar field during the radiation dominated epoch. This possibility is even greater if the quintessence field begins in a kinetic-dominated regime generated at the end of ”quintessential inflation.” As such, these models can affect, and therefore be constrained by, primordial nucleosynthesis and the epoch of photon decoupling. Here we analyze one popular form for the quintessence field (with and without a supergravity correction) and quantify constraints on the allowed initial conditions and parameters for the effective potential. We also deduce constraints on the epoch of matter creation at the end of quintessential inflation.

Constraints on resonant particle production during inflation from the matter and CMB power spectra

We analyze the limits on resonant particle production during inflation based upon the power spectrum of fluctuations in matter and the cosmic microwave background. We show that such a model is consistent with features observed in the matter power spectrum deduced from galaxy surveys and damped Lyman-{alpha} systems at high redshift. It also provides an alternative explanation for the excess power observed in the power spectrum of the cosmic microwave background fluctuations in the range of 1000<l<3500. For our best-fit models, epochs of resonant particle creation reenter the horizon at wave numbers of k{sub *}{approx}0.4 and/or 0.2 (h Mpc{sup -1}). The amplitude and location of these features correspond to the creation of fermion species of mass {approx}1-2 M{sub pl} during inflation with a coupling constant between the inflaton field and the created fermion species of near unity. Although the evidence is marginal, if this interpretation is correct, this could be one of the first observational hints of new physics at the Planck-scale.

Constraints on neutrino degeneracy from the cosmic microwave background and primordial nucleosynthesis

We reanalyze the cosmological constraints on the existence of a net universal lepton asymmetry and neutrino degeneracy based upon the latest high resolution CMB sky maps from BOOMERANG, DASI, and MAXIMA-1. We generate likelihood functions by marginalizing over

Neutrinos and Big-Bang nucleosynthesis

(\omegab h^2,\xinumt, \xinue, \Omega_\Lambda,h,n)

Impact of Few-Body Reactions on Explosive Nucleosynthesis: The Big-Bang and Supernovae

plus the calibaration uncertainties. We consider flat

Fusion Reactions in Supernovae and the Early Universe

\Omega_M + \Omega_\Lambda = 1

Nucleosynthesis in Supernovae and the Early Universe

cosmological models with two identical degenerate neutrino species,

New classes of cosmic energy and primordial black-hole formation

\xinumt \equiv \vert \xinum \vert = \vert \xinut \vert

Observational constraints on dark radiation in brane cosmology

and a small