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arXiv · 2303.17985

Inflationary gravitational wave background as a tail effect

Niko Jokela·K. Kajantie·M. Laine·Sami Nurmi·Miika Sarkkinen
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Abstract

The free propagator of a massless mode in an expanding universe can be written as a sum of two terms, a lightcone and a tail part. The latter describes a subluminal (time-like) signal. We show that the inflationary gravitational wave background, influencing cosmic microwave background polarization, and routinely used for constraining inflationary models through the so-called $r$ ratio, originates exclusively from the tail part.

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Niko Jokela, K. Kajantie, M. Laine, Sami Nurmi, Miika Sarkkinen. 2023-03-31. Inflationary gravitational wave background as a tail effect. https://doi.org/10.1103/physrevd.108.l101503

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