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Gauge-Invariant Temperature Anisotropies and Primordial Non-Gaussianity

N. Bartolo·S. Matarrese·A. Riotto
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Abstract

We provide the gauge-invariant expression for large-scale cosmic microwave background temperature fluctuations at second-order in perturbation theory. It enables to unambiguously define the nonlinearity parameter f_NL which is used by experimental collaborations to pin down the level of Non-Gaussianity in the temperature fluctuations. Furthermore, it contains a primordial term encoding all the information about the Non-Gaussianity generated at primordial epochs and about the mechanism which gave rise to cosmological perturbations, thus neatly disentangling the primordial contribution to Non-Gaussianity from the one caused by the post-inflationary evolution.

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N. Bartolo, S. Matarrese, A. Riotto. 2004-11-03. Gauge-Invariant Temperature Anisotropies and Primordial Non-Gaussianity. https://doi.org/10.1103/physrevlett.93.231301

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