Gravitational waves induced by scalar perturbations during a gradual transition from an early matter era to the radiation era

Inomata, Keisuke; Kohri, Kazunori; Nakama, Tomohiro; Terada, Takahiro

doi:10.1088/1475-7516/2019/10/071

Cited by 105 publications

(117 citation statements)

References 42 publications

(82 reference statements)

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“…Table 1 summarizes the correspondence of the notations in this paper (as well as Refs. [14,18,19,42]) and in Ref. [41].…”

Section: A Conventionmentioning

confidence: 96%

“…Gravitational waves (GWs) are a useful probe of small-scale curvature perturbations [3][4][5][6][7][8] since if the latter is enhanced, a sizable amount of GWs is produced at the second order of the cosmological perturbation. We call it the induced GWs 1 (see early works [9][10][11][12] and recent developments [13][14][15][16][17][18][19][20][21][22]). Such an enhancement of the curvature perturbations are often considered in the context of the primordial black hole (PBH) [23][24][25] (see also Refs.…”

Section: Introductionmentioning

confidence: 99%

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Gauge independence of induced gravitational waves

2020

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We study gauge (in)dependence of the gravitational waves (GWs) induced from curvature perturbations. For the GWs produced in a radiation-dominated era, we find that the observable (late-time) GWs in the TT gauge and in the Newtonian gauge are the same in contrast to a claim in the literature. We also mention the interpretation of the gauge dependence of the tensor perturbations which appears in the context of the induced GWs. arXiv:1912.00785v3 [gr-qc] 6 Jan 2020 1 It is also called the second-order GWs, secondary GWs, or scalar-induced GWs, etc.

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“…Table 1 summarizes the correspondence of the notations in this paper (as well as Refs. [14,18,19,42]) and in Ref. [41].…”

Section: A Conventionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Gauge independence of induced gravitational waves

2020

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“…(2.7) are not given by Bessel functions but by a constant and a decaying mode, although one can formally take the limit w → 0. Furthermore, an early period of matter domination (w = 0) cannot last longer than a certain amount of time, otherwise non-linearities become important [33,39,40,64]. On the other hand, if w < 0 then we get modified Bessel functions as solutions of Eq.…”

Section: Scalar Induced Gravitational Waves Reviewmentioning

confidence: 98%

“…Also, for simplicity we will assume that (re)heating is instantaneous and leave for future work any effect of a gradual change like in Ref. [39]. In this case, the spectral density of GWs at (re)heating reads…”

Section: Application To a Peaked Primordial Spectrummentioning

confidence: 99%

Induced gravitational waves in a general cosmological background

Domènech

2020

Int. J. Mod. Phys. D

132

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Gravitational waves are inevitably produced by second order terms in cosmological perturbation theory. Most notably, the so-called induced gravitational waves are a window to the small scales part of the primordial spectrum of fluctuations and a key counterpart to the primordial black hole scenario. However, semi-analytical solutions are only known for matter and radiation domination eras. In this paper, we present new analytic integral formulas for the induced gravitational waves on subhorizon scales in a general cosmological background with a constant equation of state. We also discuss applications to a peaked primordial scalar power spectrum and the primordial black hole scenario. * domenech@thphys.uni-heidelberg.de arXiv:1912.05583v3 [gr-qc] 23 Feb 20201 At linear order the identification of tensor modes with GWs is straightforward as they are gauge invariant. However, at second order is not so clear anymore. For more on this see [34,83].

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“…Ref. [977] has, however, revisited the idea by incorporating the evolution of the gravitational potentials during a gradual transition from an early MD period to the RD era, as expected in more realistic modelings of a smooth transition with a timescale comparable to the Hubble time at those moments (as it is the case in perturbative reheating scenarios with constant decay rate). They conclude that the presence of an early MD era does not enhance the induced GW background as much as originally thought.…”

Section: Inflationmentioning

confidence: 99%

The First Three Seconds: a Review of Possible Expansion Histories of the Early Universe

Allahverdi¹,

Amin²,

Berlin³

et al. 2021

TheOJA

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It is commonly assumed that the energy density of the Universe was dominated by radiation between reheating after inflation and the onset of matter domination 54,000 years later. While the abundance of light elements indicates that the Universe was radiation dominated during Big Bang Nucleosynthesis (BBN), there is scant evidence that the Universe was radiation dominated prior to BBN. It is therefore possible that the cosmological history was more complicated, with deviations from the standard radiation domination during the earliest epochs. Indeed, several interesting proposals regarding various topics such as the generation of dark matter, matter-antimatter asymmetry, gravitational waves, primordial black holes, or microhalos during a nonstandard expansion phase have been recently made. In this paper, we review various possible causes and consequences of deviations from radiation domination in the early Universe -taking place either before or after BBN -and the constraints on them, as they have been discussed in the literature during the recent years.

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Gravitational waves induced by scalar perturbations during a gradual transition from an early matter era to the radiation era

Abstract: We revisit the effects of an early matter-dominated era on gravitational waves induced by scalar perturbations. We carefully take into account the evolution of the gravita-

Cited by 105 publications

References 42 publications

Gauge independence of induced gravitational waves

Gauge independence of induced gravitational waves

Induced gravitational waves in a general cosmological background

The First Three Seconds: a Review of Possible Expansion Histories of the Early Universe

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