The gravitational-wave physics

We investigate the formation of primordial black holes (PBHs) from the collapse of spherically symmetric domain wall bubbles, which spontaneously nucleate via quantum tunneling during inflation. Since the tension of domain walls changes with time and so domain walls nucleate in a short time interval, the mass function of PBHs in general has a spike-like structure. In contrast to models in which PBHs produced from overdense regions, our model avoids the uncertainties of PBHs production mechanism. PBHs from domain walls with mass around 10 20 g may constitute all dark matter, those with mass around 10 34 g can explain the merger events of binary black holes detected by LIGO.

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“…The radius of DWs at the nucleation time is almost the same, thus R is larger for the DWs formed earlier according to Eq. (18). Substituting Eq.…”

Section: Mass Function Of Pbhsmentioning

confidence: 99%

Primordial black holes from cosmic domain walls

2020

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“…where the two time-independent polarization tensors e ij (k) andē ij (k) can be written as 4) and e i (k) andē i (k) are orthonormal basis vectors with respect to k. The source term is defined as…”

Section: Source Termmentioning

confidence: 99%

Resonant multiple peaks in the induced gravitational waves

Cai

Wang

et al. 2019

J. Cosmol. Astropart. Phys.

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We identify analytically a multiple-peak structure in the energy-density spectrum of induced gravitational waves (GWs) generated at second-order from a primordial scalar perturbations also with multiple (n) peaks at small scales k * i . The energy-density spectrum of induced GWs exhibits at most C 2 n+1 and at least n peaks at wave-vectors k ij ≡ (k * i +k * j )/ √ 3 due to resonant amplification, and, under the narrow-width approximation, it contains an universal factor that can be interpreted as a result of momentum conservation. We also extend these discussions to the case of non-Gaussian perturbations.

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“…New era of astrophysics and cosmology has arrived since the first detection of the gravitational wave (GW) event GW150914 reported by LIGO [1], and the observation of more GW events by LIGO and VIRGO [2][3][4][5][6]. With the current and the forthcoming GW experiments, including LISA [7], BBO [8], KAGRA [9], ET [10], Taiji [11,12] and Tian-Qin [13], the GWs have opened a new window to explore the nature of gravity [14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Propagation of gravitational waves in a cosmological background

Gao

Hong

2020

Phys. Rev. D

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We investigate the propagation of the gravitational waves in a cosmological background. Based on the framework of spatially covariant gravity, we derive the general quadratic action for the gravitational waves. The spatial derivatives of the extrinsic curvature and the parity-violating terms are systematically introduced. Special attention is paid to the propagation speed of the gravitational waves. We find that it is possible to make the two polarization modes propagate in the same speed, which may differ from that of the light, in the presence of parity-violating terms in the action. In particular, we identify a large class of spatially covariant gravity theories with parity violation, in which both the polarization modes propagate in the speed of light. Our results imply that there are more possibilities in the framework of spatially covariant gravity in light of the propagation speed of the gravitational waves. *

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The gravitational-wave physics

Cited by 168 publications

References 108 publications

Primordial black holes from cosmic domain walls

Primordial black holes from cosmic domain walls

Resonant multiple peaks in the induced gravitational waves

Propagation of gravitational waves in a cosmological background

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