Searching for inflation in simple string theory models: An astrophysical perspective

Mark P. Hertzberg, Max Tegmark, Shamit Kachru, Jessie Shelton, and Onur Özcan
Phys. Rev. D 76, 103521 – Published 13 November 2007

Abstract

Attempts to connect string theory with astrophysical observation are hampered by a jargon barrier, where an intimidating profusion of orientifolds, Kähler potentials, etc. dissuades cosmologists from attempting to work out the astrophysical observables of specific string theory solutions from the recent literature. We attempt to help bridge this gap by giving a pedagogical exposition with detailed examples, aimed at astrophysicists and high energy theorists alike, of how to compute predictions for familiar cosmological parameters when starting with a 10-dimensional string theory action. This is done by investigating inflation in string theory, since inflation is the dominant paradigm for how early universe physics determines cosmological parameters. We analyze three explicit string models from the recent literature, each containing an infinite number of vacuum solutions. Our numerical investigation of some natural candidate inflatons, the so-called “moduli fields,” fails to find inflation. We also find in the simplest models that, after suitable field redefinitions, vast numbers of these vacua differ only in an overall constant multiplying the effective inflaton potential, a difference which affects neither the potential’s shape nor its ability to support slow-roll inflation. This illustrates that even having an infinite number of vacua does not guarantee having inflating ones. This may be an artifact of the simplicity of the models that we study. Instead, more complicated string theory models appear to be required, suggesting that identifying the inflating subset of the string landscape will be challenging.

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  • Received 4 September 2007

DOI:https://doi.org/10.1103/PhysRevD.76.103521

©2007 American Physical Society

Authors & Affiliations

Mark P. Hertzberg1,*, Max Tegmark1, Shamit Kachru2, Jessie Shelton1,3, and Onur Özcan1

  • 1Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
  • 2Department of Physics and SLAC, Stanford University, Stanford, California 94305, USA
  • 3Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08855, USA

  • *mphertz@mit.edu

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Vol. 76, Iss. 10 — 15 November 2007

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