Takahiro Tanaka, Yuko Urakawa
The primordial perturbation is widely accepted to be generated through the vacuum fluctuation of the scalar field which drives inflation. It is, however, not completely clear what is the natural vacuum in the inflationary universe particularly in the presence of non-linear interactions. In this series of papers, we will address this issue, focusing on the condition required for the removal of the divergence from the infrared contribution to loop diagrams. The IR regularity is deeply related to preserving the coordinate independence in describing the local observable universe. In our previous works, the IR regularity condition was discussed using the slow roll expansion, which restricts the background evolution of the inflationary universe. We will show more generally that the absence of infrared divergence leads to non-trivial constraints on the allowed quantum states.
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http://arxiv.org/abs/1209.1914
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