Implications of the NANOGrav result on primordial gravitational waves in nonstandard cosmologies

Show simple item record Bhattacharya, Sukannya Mohanty, Subhendra Parashari, Priyank
dc.coverage.spatial United States of America 2021-05-14T05:18:42Z 2021-05-14T05:18:42Z 2021-03
dc.identifier.citation Bhattacharya, Sukannya; Mohanty, Subhendra and Parashari, Priyank, "Implications of the NANOGrav result on primordial gravitational waves in nonstandard cosmologies", Physical Review D, DOI: 10.1103/PhysRevD.103.063532, vol. 103, no. 6, Mar. 2021. en_US
dc.identifier.issn 2470-0010
dc.identifier.issn 2470-0029
dc.description.abstract Recently, the NANOGrav Collaboration has reported evidence for a common-spectrum stochastic process, which might be interpreted as the first ever detection of stochastic gravitational wave (GW) background. We discuss the possibility of the signal arising from the first- and second-order GWs in nonstandard cosmological history. We show that the NANOGrav observation can be explained by firstorder GWs in the nonstandard thermal history with an early matter-dominated era, whereas the parameter space required to explain the NANOGrav observation in the standard cosmology or in the nonstandard epoch of kination domination is ruled out by the big bang nucleosynthesis and cosmic microwave background observations. For the second-order GWs arising from the large primordial scalar fluctuations, we study the standard radiation domination and two specific nonstandard cases with a few forms of the primordial power spectrum P??k? to achieve abundant primordial black hole (PBH) production. We find that the NANOGrav observation can be explained with standard radiation domination for all of these P??k?. Furthermore, a dustlike epoch leads to abundant PBH formation for a lower amplitude of P??k? than the radiation-dominated case and complies with the NANOGrav observation only for a few of the P??k? forms considered here, where the peak wave number is larger than the wave number range probed by NANOGrav. In this nonstandard epoch, for a brod power spectrum, PBHs are produced in a wide massrange in the planetary mass regime. A nonstandard epoch of kination domination cannot produce enough PBHs for anyof the P??k? if the NANOGrav result is to be satisfied.
dc.description.statementofresponsibility by Sukannya Bhattacharya, Subhendra Mohanty and Priyank Parashari
dc.format.extent vol. 103, no. 6
dc.language.iso en_US en_US
dc.publisher American Physical Society en_US
dc.subject Research Areas en_US
dc.subject Dark matter en_US
dc.subject Evolution of the Universe en_US
dc.subject Gravitational waves en_US
dc.subject Gravitation en_US
dc.subject Cosmology & Astrophysics en_US
dc.title Implications of the NANOGrav result on primordial gravitational waves in nonstandard cosmologies en_US
dc.type Article en_US
dc.relation.journal Physical Review D

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