Dilaton dynamics from production of tensionless membranes

Abstract

In this paper we consider classical and quantum corrections to cosmological solutions of 11D SUGRA coming from dynamics of membrane states. We first consider the supermembrane spectrum following the approach of Russo and Tseytlin for consistent quantization. We calculate the production rate of BPS membrane bound states in a cosmological background and find that such effects are generically suppressed by the Planck scale, as expected. However, for a modified brane spectrum possessing enhanced symmetry, production can be finite and significant. We stress that this effect could not be anticipated given only a knowledge of the low-energy effective theory. Once on-shell, inclusion of these states leads to an attractive force pulling the dilaton towards a fixed point of S-duality, namely g s = 1. Although the SUGRA description breaks down in this regime, inclusion of the enhanced states suggests that the center of M-theory moduli space is a dynamical attractor. Morever, our results seem to suggest that string dynamics does indeed favor a vacuum near fixed points of duality. * Electronic address: sera@het.brown.edu † Electronic address: watsongs@physics.utoronto.ca

How well can we really determine the scale of inflation?

“…The time dependent mass and tension appearing in (20) and (21) can lead to interesting cosmological implications. In models of moduli trapping [17,18,35,36] the particle production resulting from the scalar's time dependence was shown to lead to dynamical stabilization of moduli (massless scalars) that would otherwise have little or no potential and remain unstablized. When identified as the inflaton, it was shown in [19,37] that when accounting for the effects of particle production one can obtain slow-roll inflation from potentials that would otherwise not satisfy the slow-roll conditions.…”

“…Interactions captured by (22) generically occur within the context of string theory and M-theory model building. Common examples include the presence of new light states (here represented as χ) as the size of a compact dimension or internal cycle (parametrized by ϕ) shrink and the symmetries of the theory become enhanced [18,35] -i.e. there is an inverse string Higgs effect.…”

Radion effective potential in brane gas cosmology

“…Despite the promising result, we have to be very careful when we stabilize both dilaton and radion simultaneously. Cremonini and Watson [22] have discussed the stabilization of moduli in eleven dimensional supergravity. They found that the production rate of the BPS bound states could be significant for a modified brane spectrum with enhanced symmetry.…”

Was the Universe actually radiation dominated prior to nucleosynthesis?

“…Our results, as well as those of [36], suggest that if one is to eliminate the moduli dominated epoch one is going to have to consider moduli that are strongly coupled. There is some motivation for this in string theory [37] (for more recent work see [38]), however there must typically be at least one light modulus if we are to realize the perturbative Standard Model in a string construction [22]. For this reason, we take our results as a robust prediction that string theories lead to the expectation for a prolonged, matter-dominated epoch prior to BBN.…”