Polarization of a stochastic gravitational wave background through diffusion by massive structures

Cusin, Giulia; Durrer, Ruth; Ferreira, Pedro G.

doi:10.1103/physrevd.99.023534

Cited by 53 publications

(88 citation statements)

References 106 publications

(161 reference statements)

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“…(1.43) would be a 4-index symmetric transverse (to both p µ and u µ ) traceless tensor, whose multipolar decomposition is performed as in Eq. (1.59) but with spin-4 spherical harmonics (Cusin et al, 2018a).…”

Section: Resultsmentioning

confidence: 99%

Radiative transport of relativistic species in cosmology

Pitrou

2021

Astroparticle Physics

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Je résume les étapes essentielles de la construction d'une fonction de distribution pour les gaz de fermions et de bosons (photons), en mettant en exergue les points communs et les différences entre ces deux cas. L'objet central qui caractérise la polarisation des photons est une fonction de distribution à valeurs tensorielles, tandis que pour les fermions elle prend des valeurs vectorielles. Les termes de collision des équations de Boltzmann associées aux fermions et aux bosons possèdent également une structure semblable, et ils ne diffèrent essentiellement qu'à cause des effets quantiques associés à l'état final des réactions considérées. En particulier, les réactions de conversion entre neutrons et protons dans l'univers primordial, qui déterminent l'abondance de l'Helium, ont de nombreux points communs avec les diffusions Compton qui déterminent la forme du fond diffus cosmologique, et je montre que ces deux classes de réactions peuvent être calculées avec un développement de type Fokker-Planck. Pour les conversions neutronsprotons, cela permet d'obtenir les corrections dues à la masse finie des nucléons et qui s'avèrent être cruciales pour obtenir des prédictions théoriques précises, tandis que dans le cas des diffusions Compton cela permet d'obtenir les effets thermaux et de recul des électrons qui sont pris en compte dans la célèbre équation de Kompaneets. Dans ce mémoire, je généralise celle-ci au cas d'une distribution de radiation anisotrope et potentiellement polarisée. Enfin, je discute une paramétrisation du spectre des photons basée sur l'utilisation de moments logarithmiques, ce qui permet de séparer proprement les effets qui induisent une variation de température de ceux qui génèrent une distorsion du spectre de corps noir.

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Section: Resultsmentioning

confidence: 99%

Radiative transport of relativistic species in cosmology

Pitrou

2021

Astroparticle Physics

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“…However, future detectors will allow for a better angular resolution of anisotropies of the astrophysical background. Therefore, another tool could be the directionality dependence of the SGWB [14][15][16][17][18][19] and, as we explore here, its statistics.…”

Section: Introductionmentioning

confidence: 99%

Characterizing the cosmological gravitational wave background: Anisotropies and non-Gaussianity

et al. 2020

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A future detection of the stochastic gravitational wave background (SGWB) with gravitational wave (GW) experiments is expected to open a new window on early universe cosmology and on the astrophysics of compact objects. In this paper we study SGWB anisotropies, that can offer new tools to discriminate between different sources of GWs. In particular, the cosmological SGWB inherits its anisotropies both (i) at its production and (ii) during its propagation through our perturbed universe. Concerning (i), we show that it typically leads to anisotropies with order one dependence on frequency. We then compute the effect of (ii) through a Boltzmann approach, including contributions of both large-scale scalar and tensor linearized perturbations. We also compute for the first time the three-point function of the SGWB energy density, which can allow one to extract information on GW non-Gaussianity with interferometers. Finally, we include nonlinear effects associated with long wavelength scalar fluctuations, and compute the squeezed limit of the 3-point function for the SGWB density contrast. Such limit satisfies a consistency relation, conceptually similar to that found in the literature for the case of cosmic microwave background perturbations.

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“…Even assuming a completely homogeneous and isotropic SGWB at its production, these GWs propagate in a perturbed universe. As a consequence, the GW signal arriving to Earth has angular anisotropies [37][38][39][40][41][42][43] which are non-Gaussian [44]. In addition, as we show and quantify in this work, the GW production itself has some degree of anisotropy and non-Gaussianity.…”

Section: Introductionmentioning

confidence: 99%

Gravitational wave anisotropies from primordial black holes

Bartolo

Bertacca

Luca

et al. 2020

J. Cosmol. Astropart. Phys.

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An observable stochastic background of gravitational waves is generated whenever primordial black holes are created in the early universe thanks to a small-scale enhancement of the curvature perturbation. We calculate the anisotropies and non-Gaussianity of such stochastic gravitational waves background which receive two contributions, the first at formation time and the second due to propagation effects. We conclude that a sizeable magnitude of anisotropy and non-Gaussianity in the gravitational waves would suggest that primordial black holes may not comply the totality of the dark matter.

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Polarization of a stochastic gravitational wave background through diffusion by massive structures

Cited by 53 publications

References 106 publications

Radiative transport of relativistic species in cosmology

Radiative transport of relativistic species in cosmology

Characterizing the cosmological gravitational wave background: Anisotropies and non-Gaussianity

Gravitational wave anisotropies from primordial black holes

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