Journal
PHYSICAL REVIEW D
Volume 86, Issue 12, Pages -Publisher
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevD.86.123502
Keywords
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Funding
- Ministry of Education, Science, Sports, and Culture (MEXT), Japan [22540263, 22244021, 23104001, 21111006, 22244030]
- Grants-in-Aid for Scientific Research [22244030, 22540263, 21111006] Funding Source: KAKEN
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Recent cosmological observations indicate the existence of extra light species, i.e., dark radiation. In this paper we show that signatures of the dark radiation are imprinted in the spectrum of inflationary gravitational waves. If the dark radiation is produced by the decay of a massive particle, high frequency modes of the gravitational waves are suppressed. In addition, due to the effect of the anisotropic stress caused by the dark radiation, a dip in the gravitational wave spectrum may show up at the frequency which enters the horizon at the time of the dark radiation production. Once the gravitational wave spectrum is experimentally studied in detail, we can infer the information on how and when the dark radiation was produced in the Universe.
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