Possible origin of CMB temperature fluctuations: Vacuum fluctuations of Kaluza-Klein and string states during inflationary era

Abstract

We point out that the temperature fluctuations of cosmic microwave background (CMB) can be generated in a way that is different from the one usually assumed in slow-roll inflation. Our mechanism is based on vacuum fluctuations of fields which are at rest at the bottom of the potential, such as Kaluza-Klein modes or string excited states. When there are a large number (typically of order $N\sim 10^{14}$) of fields with small mass in unit of Hubble parameter during the inflationary era, this effect can give significant contributions to the CMB temperature fluctuations. This number $N$ makes it possible to enhance scalar perturbation relative to tensor perturbation. Comparison with the observed amplitudes suggests that models with string scale of order $10^{-5}$ of 4D Planck scale are favorable.

32 pages, 7 figures; v2: Corrected minor misprints in Appendix. Added references; v3: Added discussion about reheating in Subsection 5.1. Added references. Final version to appear in PRD

References in corpus (8)

• Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
• Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
• Non-Gaussianities in Single Field Inflation and their Optimal Limits from the WMAP 5-year Data
• Vector Inflation
• Particle physics models of inflation and curvaton scenarios
• Reheating for Closed String Inflation
• Inflation in string theory: a graceful exit to the real world
• CMB Fluctuations and String Compactification Scales

Cited by in corpus (2)

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