Semianalytic calculation of gravitational wave spectrum nonlinearly induced from primordial curvature perturbations

By K. Kohri, T. Terada. Physical Review D, 2018

466 citations recorded by the source corpus.

Whether or not the primordial gravitational wave (GW) produced during inflation is sufficiently strong to be observable, GWs are necessarily produced from the primordial curvature perturbations in the second order of perturbation. The induced GWs can be enhanced by curvature perturbations enhanced at small scales or by the presence of matter-dominated stages of the cosmological history. We analytically calculate the integral in the expression of the power spectrum of the induced GWs which is a universal part independent of the spectrum of the primordial curvature perturbations. This makes the subsequent numerical integrals significantly easy. In simple cases, we derive fully analytic formulas for the induced GW spectrum.

Subfields: Astronomy and Astrophysics, Oceanography

View Paper: https://www.semanticscholar.org/paper/f1062248331b882243b56c34b6693859a4d9d58c

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Citations in the corpus

Primordial black holes and gravitational waves from parametric amplification of curvature perturbations (2019, background): “On the other hand, those large curvature perturbations, as source of the tensor perturbations, would result in an isotropic stochastic gravitational wave (GW) background observable today [23–43].”
Gravitational wave constraints on the primordial black hole dominated early universe (2020, background): “First, for a sharp peak in the primordial curvature power spectrum with amplitude AR, the peak of the induced GW is at k ∼ 2kf/ √ 3 with amplitude Ωead GW,c∼ 21A(2)R [36, 48], where kf is the scale corresponding to the horizon at formation and ead refers to early adiabatic mode.”
Non-Gaussianity and the induced gravitational wave background (2021, background): “The Gaussian result is [53] ΩGW(k)Gaussian = 3A(2)R 1024 k̃ 2Θ(2− k̃) ( k̃2 − 4 )2 ( 3k̃2 − 2 )2 (3.”
Challenges and opportunities of gravitational-wave searches at MHz to GHz frequencies (2020, background): “In particular, density perturbations can produce ‘induced’ (or ‘secondary’) GWs through a ζ + ζ → h process [89–91] (see also [92–94]).”
Gravitational waves induced by scalar perturbations with a lognormal peak (2020, background): “[28], we define a set of new variables, u = |k − `|/k, and v = `/k, and then integrate the solid angular elements perpendicular to ˆ̀- and q̂-direction in (2.”
Oscillations in the stochastic gravitational wave background from sharp features and particle production during inflation (2020, background): “8For GWs induced by scalar fluctuations during a period of matter-domination the corresponding integration kernel TMD(d, s) is derived in [53].”
Solar-mass primordial black holes explain NANOGrav hint of gravitational waves (2020, background): “8 × 10−6 from the (non-)adiabatic Neff bound of big-bang nucleosynthesis [42].”
Induced gravitational waves as a probe of thermal history of the universe (2020, methodology): “[69, 70] for w = 1/3 (see appendix H) and ref.”
Steepest growth of the power spectrum and primordial black holes (2018, methodology): “For this reason, we utilise the explicit analytic form of the kernel K(τ, u, v) detailed in [108] in what follows — for the purposes of placing observational bounds, it is also the more conservative choice because it leads to a lower normalisation of ΩGW than several other references.”
Gravitational waves induced by scalar perturbations during a gradual transition from an early matter era to the radiation era (2019, methodology): “[10, 26, 27].”
Gravitational waves from a universe filled with primordial black holes (2020, methodology): “Since a gas of randomly distributed PBHs is associated with a densityfluctuation field, at second order in perturbation theory [20, 21], these scalar fluctuations are expected to source the production of tensor perturbations [22–24], thus inducing a stochastic gravitational-wave background [25].”