paper

Gravitational Waves Induced by Scalar Perturbations with a Lognormal Peak

arXiv:2005.12306 · doi:10.1088/1475-7516/2020/09/037

Abstract

We study the stochastic gravitational wave (GW) background induced by the primordial scalar perturbation with the spectrum having a lognormal peak of width at . We derive an analytical formula for the GW spectrum for both narrow () and broad () peaks. In the narrow-peak case, the spectrum has a double peak feature with the sharper peak at . On the infrared (IR) side of the spectrum, we find power-law behavior with a break at in the power-law index where it chages from on the far IR side to on the near IR side. We find the ratio of the break frequency to the peak frequency is determined by as , where and are the break and peak frequencies, respectively. In the broad-peak case, we find the GW spectrum also has a lognormal peak at but with a smaller width of . Using these derived analytic formulae, we also present expressions for the maximum values of for both narrow and broad cases. Our results will provide a useful tool in searching for the induced GW signals in the coming decades.

15 pages, 3 figures. Some figures redrawn. References added and reorganized. Accepted for JCAP

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