Enhancing gravitational wave anisotropies with peaked scalar sources

Dimastrogiovanni, Emanuela; Fasiello, Matteo; Malhotra, Ameek; Tasinato, Gianmassimo

doi:10.48550/arxiv.2205.05644

Cited by 5 publications

(10 citation statements)

References 115 publications

(159 reference statements)

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“…in refs. [56][57][58][59][60][61]. In addition to these we can have anisotropies sourced by some primordial production mechanism that will be present at the formation of the inflationary CGWB.…”

Section: Introductionmentioning

confidence: 99%

Probing parity-odd bispectra with anisotropies of GW V modes

Orlando

2022

J. Cosmol. Astropart. Phys.

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It is well known that non-trivial squeezed tensor bispectra can lead to anisotropies in the inflationary stochastic gravitational wave (GW) background, providing us with an alternative and complementary window to primordial non-Gaussianities (NGs) with respect to the CMB. Previous works have highlighted the detection prospects of parity-even tensor NGs via the GW I-mode anisotropies. In this work we extend this by analysing for the first time the additional information carried by GW V-mode anisotropies due to squeezed NGs. We show that GW V modes allow us to probe parity-odd squeezed 〈 tts 〉 and 〈 ttt 〉 bispectra. These bispectra break parity at the non-linear level and can be introduced by allowing alternative symmetry breaking patterns during inflation, like those comprised in solid inflation. Considering a BBO-like experiment, we find that a non-zero detection of squeezed 〈 tts 〉 parity-odd bispectra in the V modes dipole is possible without requiring any short-scale enhancement of the GW power spectrum amplitude over the constraints set by the CMB. We also briefly discuss the role of V-CMB cross-correlations. Our work can be extended in several directions and motivates a systematic search for polarized GW anisotropies in the next generations of GW experiments.

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Section: Introductionmentioning

confidence: 99%

Probing parity-odd bispectra with anisotropies of GW V modes

Orlando

2022

J. Cosmol. Astropart. Phys.

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“…[17,18]) of the latter would reveal the details of different physical processes in the inflationary era. The study of the SGWB intensity [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] has been performed so far with approaches similar to those used for the Cosmic Microwave Background (CMB): its evolution is described by a phase-space distribution function obeying the collisionless Boltzmann equation in a background perturbed by the Large Scale Structure (LSS) of the universe [16,[35][36][37][38]. This approximation applies in the so-called geometrical optics limit [39][40][41][42][43], i.e.…”

Section: Introductionmentioning

confidence: 99%

Boltzmann equations for astrophysical Stochastic Gravitational Wave Backgrounds scattering off of massive objects

Pizzuti¹,

Alessandro²,

Carbone³

et al. 2022

Preprint

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We present a set of coupled Boltzmann equations describing the intensity and polarisation Stokes parameters of the SGWB, including collision terms which account for gravitational Compton scattering off of massive objects. This set resembles that for the CMB Stokes parameters, but the different spin nature of the gravitational radiation and the physics involved in the scattering process determine crucial differences. In the case of gravitational Compton scattering, due to the Rutherford angular dependence of the cross section, all the SGWB intensity multipoles of order are scattered out, therefore producing outgoing intensity anisotropies of any order if they are present in the incoming radiation. SGWB linear polarisation modes can be generated from unpolarised anisotropic radiation only with m = ±4, which requires at least a hexadecapole anisotropy ( ≥ 4) in the incoming intensity. We confirm the contribution of the gravitational Compton scattering to the SGWB anisoptropies is extremely small for collisions with massive compact objects (BH and SMBH) in the frequency range of current and upcoming surveys. However, we stress that the system of coupled Boltzmann equations presented here provides an accurate estimate of the total amount of anisotropies generated by multiple SGWB scattering processes off of massive objects, as well as the interplay between polarisation and intensity, during the GW propagation across the LSS of the universe. These results will be useful for the full treatment of the astrophysical SWGB anisotropies in view of upcoming gravitational waves observatories.

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“…In recent years, the secondary GWs induced by the nonlinear coupling of scalar perturbations have been attracting great attention. Those are regarded as a reasonable tool to detect a type of ultra-compact objects that may exist in the early Universe -primordial black holes (PBHs) [11][12][13][14][15][16][17][18][19][20][21][22], and to probe the statistical properties of the small-scale primordial curvature perturbations [23][24][25][26][27][28][29]. Overdense regions in the early Universe may stop expanding and collapse to form PBHs [30][31][32].…”

Section: Introductionmentioning

confidence: 99%

Missing one-loop contributions in secondary gravitational waves

Chen¹,

Ota²,

Zhu³

et al. 2022

Preprint

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We find several missing one-loop-order contributions in previous considerations about secondary gravitational waves induced at nonlinear order in cosmological perturbations. We consider a consistent perturbative expansion to third-order in cosmological perturbations, including higher-order interactions and iterative solutions ignored in the previous literature. Tensor fluctuations induced by the source with two scalar and one tensor perturbations are correlated with the first-order tensor fluctuation and thus give a one-loop-order correction to the tensor power spectrum. The missing loop correction is scale-invariant and negative in the superhorion region, which secondarily reduces the initial primordial tensor power spectrum prior to the horizon re-entry. Such an IR behavior is very different from the auto-spectrum of second-order induced tensor modes discussed in the previous literature and can be important for the actual gravitational wave measurements. For a sharp peak of scalar fluctuations with A ζ = 10 −2 at k * = 10 5 h/Mpc motivated by the LIGO/Virgo events, we show that the tensor power spectrum at the cosmic microwave background scale reduces by at most 35%. Hence, the polarization B-mode might not be seen because of the reduction of the original tensor spectrum due to the secondary effect of primordial black hole formation.

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Enhancing gravitational wave anisotropies with peaked scalar sources

Cited by 5 publications

References 115 publications

Probing parity-odd bispectra with anisotropies of GW V modes

Probing parity-odd bispectra with anisotropies of GW V modes

Boltzmann equations for astrophysical Stochastic Gravitational Wave Backgrounds scattering off of massive objects

Missing one-loop contributions in secondary gravitational waves

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