Detecting relics of a thermal gravitational wave background in the early Universe |
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Authors: | Wen Zhao Deepak Baskaran Peter Coles |
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Affiliation: | aSchool of Physics and Astronomy, Cardiff University, Cardiff, CF24 3AA, United Kingdom;bWales Institute of Mathematical and Computational Sciences, Swansea, SA2 8PP, United Kingdom;cDepartment of Physics, Zhejiang University of Technology, Hangzhou 310014, People's Republic of China |
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Abstract: | A thermal gravitational wave background can be produced in the early Universe if a radiation dominated epoch precedes the usual inflationary stage. This background provides a unique way to study the initial state of the Universe. We discuss the imprint of this thermal spectra of gravitons on the cosmic microwave background (CMB) power spectra, and its possible detection by CMB observations. Assuming the inflationary stage is a pure de Sitter expansion we find that, if the number of e-folds of inflation is smaller than 65, the signal of this thermal spectrum can be detected by the observations of Planck and PolarBear experiments, or the planned EPIC experiments. This bound can be even looser if inflation-like stage is the sub-exponential. |
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Keywords: | 98.70.Vc 98.80.Cq 04.30.-w |
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