Signatures of short distance physics in the cosmic microwave background

Nemanja Kaloper, Matthew Kleban, Albion Lawrence, and Stephen Shenker
Phys. Rev. D 66, 123510 – Published 26 December 2002
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Abstract

We systematically investigate the effect of short distance physics on the spectrum of temperature anisotropies in the cosmic microwave background produced during inflation. We present a general argument—assuming only low-energy locality—that the size of such effects is of order H2/M2, where H is the Hubble parameter during inflation and M is the scale of the high-energy physics. We evaluate the strength of such effects in a number of specific string and M theory models. In weakly coupled field theory and string theory models, the effects are far too small to be observed. In phenomenologically attractive Hořava-Witten compactifications, the effects are much larger but still unobservable. In certain M theory models, for which the fundamental Planck scale is several orders of magnitude below the conventional scale of grand unification, the effects may be on the threshold of detectability. However, observations of both the scalar and tensor fluctuation contributions to the cosmic microwave background power spectrum—with a precision near the cosmic variance limit—are necessary in order to demonstrate unambiguously the existence of these signatures of high-energy physics. This is a formidable experimental challenge.

  • Received 28 June 2002

DOI:https://doi.org/10.1103/PhysRevD.66.123510

©2002 American Physical Society

Authors & Affiliations

Nemanja Kaloper1, Matthew Kleban1, Albion Lawrence1,2, and Stephen Shenker1

  • 1Department of Physics, Stanford University, Stanford, California 94305
  • 2SLAC Theory Group, MS 81, 2575 Sand Hill Road, Menlo Park, California 94025

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Issue

Vol. 66, Iss. 12 — 15 December 2002

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