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Multimessenger cosmology: Correlating cosmic microwave background and stochastic gravitational wave background measurements

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Peter Adshead, Niayesh Afshordi, Emanuela Dimastrogiovanni, Matteo Fasiello, Eugene A. Lim, Gianmassimo Tasinato

Original languageEnglish
Article number023532
JournalPhysical Review D
Volume103
Issue number2
DOIs
Published26 Jan 2021

Bibliographical note

Funding Information: We are delighted to thank Ameek Malhotra for insightful input on Sec. . The work of P. A. was supported by the US Department of Energy through Grant No. DE-SC0015655. N. A. acknowledges support by the University of Waterloo, Natural Sciences and Engineering Research Council of Canada, and the Perimeter Institute for Theoretical Physics (PITP). Research at P. I. T. P. is supported in part by the Government of Canada through the Department of Innovation, Science and Economic Development Canada and by the Province of Ontario through the Ministry of Colleges and Universities. The work of M. F. is supported in part by the UK STFC Grant No. ST/S000550/1 and the “Atracción de Talento” Grant No. 2019-T1/TIC-15784. E. A. L. is supported by an STFC AGP-AT grant (No. ST/P000606/1). The work of G. T. is partially funded by STFC Grant No. ST/P00055X/1. P. A., E. D., and M. F. acknowledge the hospitality of the Kavli Institute for Theoretical Physics, which is supported in part by the National Science Foundation under Grant No. NSF-PHY-1748958. We thank the organizers of the “Gravitational Waves from the Early Universe” workshop at NORDITA for their hospitality where some of this work was done. Publisher Copyright: © 2021 American Physical Society. Copyright: Copyright 2021 Elsevier B.V., All rights reserved.

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Abstract

Characterizing the physical properties of the stochastic gravitational wave background (SGWB) is a key step towards identifying the nature of its possible origin. We focus our analysis on SGWB anisotropies. The existence of a nontrivial primordial scalar-tensor-tensor (STT) correlation in the squeezed configuration may be inferred from the effect that a long wavelength scalar mode has on the gravitational wave power spectrum: an anisotropic contribution. Crucially, such a contribution is correlated with temperature anisotropies in the cosmic microwave background (CMB). We show that, for inflationary models that generate suitably large STT non-Gaussianities, cross correlating the CMB with the stochastic background of gravitational waves is a very effective probe of early universe physics. The resulting signal can be a smoking gun for primordial SGWB anisotropies.

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