Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Red and blue tilted tensor spectrum from Gibbons-Hawking temperature   The scale invariant scalar and tensor perturbations, which are predicted from
inflation, are eigenmodes in the conformal coordinates. The 'out' observer in
the de Sitter space observes a thermal spectrum with a Gibbons-Hawking
temperature $H/2\pi$ of these 'Bunch-Davies' particles. The tensor power
spectrum observed in experiments can have an imprint of the Gibbons-Hawking
thermal distribution due to the mode mixing between 'in' state conformal
coordinates and the coordinate frame of the observer. We find that the the
Bunch-Davies modes appear as thermal modes to the asymptotic Minkowski observer
in the future and the power spectrum of the gravitational waves is blue-tilted
with a spectral index $n_T \sim 1$ even in the standard slow-roll inflation. On
the other hand if the coordinate frame of the observer is taken to be static
coordinates, the tensor spectrum is red-tilted with $n_T\sim -1$. A likelihood
analysis shows and find the best fit values of the slow-roll parameters for
both cases. We find that the blue-tilted tensor gives a better fit and
reconciles the PLANCK upper bound on the tensor-to-scalar ratio, $r <0.11$ with
BICEP2 measurement of $r=0.2$. This supports the idea of particle production
due to the mode mixing between the initial Bunch-Davies vacuum modes and the
asymptotic Minkowski vacuum of the post-inflation universe.

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The categories of this paper are: math
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The categories of this paper are: math-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: supr-con
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The categories of this paper are: quant-ph
30
The categories of this paper are: q-alg
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The categories of this paper are: alg-geom
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The categories of this paper are: solv-int
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The categories of this paper are: nlin
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The categories of this paper are: hep-ex
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The categories of this paper are: nucl-ex
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The categories of this paper are: comp-gas
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The categories of this paper are: stat
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The categories of this paper are: bayes-an
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The categories of this paper are: funct-an
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The categories of this paper are: physics