Testing the early universe with anisotropies of the gravitational wave background

Dimastrogiovanni, Emanuela; Fasiello, Matteo; Malhotra, Ameek; Meerburg, P. Daniel; Orlando, Giorgio

doi:10.1088/1475-7516/2022/02/040

Cited by 26 publications

(33 citation statements)

References 116 publications

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“…On the other hand, anisotropies are expected, both of primordial origin, or induced by propagation effects from the early universe to today: see e.g. [57][58][59][60][61][62][63][64][65]. For example, sizeable intrinsic quadrupolar anisotropies can be produced in scenarios with large tensor non-Gaussianity, see e.g.…”

Section: Jcap08(2022)036mentioning

confidence: 99%

Doppler boosting the stochastic gravitational wave background

Cusin

Tasinato

2022

J. Cosmol. Astropart. Phys.

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One of the guaranteed features of the stochastic gravitational wave background (SGWB) is the presence of Doppler anisotropies induced by the motion of the detector with respect to the rest frame of the SGWB source. We point out that kinematic effects can be amplified if the SGWB is characterised by large tilts in its spectrum as a function of frequency, or by sizeable intrinsic anisotropies. Hence we examine the possibility to use Doppler effects as complementary probes of the SGWB frequency profile. For this purpose we work in multipole space, and we study the effect of kinematic modulation and aberration on the GW energy density parameter and on its angular power spectrum. We develop a Fisher forecast analysis and we discuss prospects for constraining parameters controlling kinematically induced anisotropies with future detector networks. As a case study, we apply our framework to a background component with constant slope in frequency, potentially detectable by a network of future ground-based interferometers. For this specific example, we show that a measurement of kinematic anisotropies with a network of Einstein Telescope and Cosmic Explorer will allow us to constrain the spectral shape with a precision of about 16%. We also show that, if a reconstruction of the spectral shape is done via other methods, e.g. frequency binning, a study of kinematic anisotropies can allow one to constrain our peculiar velocity with respect to the CMB frame with a precision of 30%. Finally, we identify cosmological and astrophysical scenarios where kinematic effects are enhanced in frequency ranges probed by current and future GW experiments.

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Section: Jcap08(2022)036mentioning

confidence: 99%

Doppler boosting the stochastic gravitational wave background

Cusin

Tasinato

2022

J. Cosmol. Astropart. Phys.

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“…In the following, we provide the spherical harmonic coefficients obtained by considering angular dependencies that typically appear in the literature, referring to the original refs. [67,68] and appendix C for computational details.…”

Section: Intrinsic Anisotropies From Squeeezed Bispectramentioning

confidence: 99%

“…(3.33) 12 Here and in the following we will re-normalize the F λ 1 ...λn, x 1 x 2 x 3 NL (k, q) coefficients in order to be coherent with the normalization chosen in literature [68]. This allows for better comparison of these results with previous works.…”

Section: Monopolar γγζmentioning

confidence: 99%

“…As the fractional energy density per logarithmic wave-number of the CGWB from inflation is by definition linearly related to the tensor power spectrum, these inhomogeneities result in intrinsic anisotropies already present at the formation of the inflationary CGWB. Previous works have mostly studied the theoretical predictions and the detection prospects for the anisotropies induced by squeezed parity invariant tensor-tensorscalar ( tts ) and tensor-tensor-tensor ( ttt ) bispectra [65][66][67][68][69]. 2 It was shown that they give non-zero I(Intensity)-mode anisotropies to the GW background from inflation.…”

Section: Introductionmentioning

confidence: 99%

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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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“…[28][29][30][31][32] and in particular [33] for a recent study). But, as for the CMB, it is potentially well larger than intrinsic cosmological anisotropies (see, e.g., the studies [34][35][36][37][38][39][40]). Kinematic anisotropies is a topic of active research in the context of GW interferometers [23,[41][42][43][44][45].…”

Section: Introductionmentioning

confidence: 99%

Kinematic anisotropies and pulsar timing arrays

Tasinato

2023

Phys. Rev. D

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Doppler anisotropies, induced by our relative motion with respect to the source rest frame, are a guaranteed property of stochastic gravitational wave backgrounds of cosmological origin. If detected by future pulsar timing array measurements, they will provide interesting information on the physics sourcing gravitational waves, which is hard or even impossible to extract from measurements of the isotropic part of the background only. We analytically determine the pulsar response function to kinematic anisotropies, including possible effects due to parity violation, to features in the frequency dependence of the isotropic part of the spectrum, as well as to the presence of extra scalar and vector polarizations. For the first time, we show how the sensitivity to different effects crucially depends on the pulsar configuration with respect to the relative motion among frames. Correspondingly, we propose examples of strategies of detection, each aimed at exploiting future measurements of kinematic anisotropies for characterizing distinct features of the cosmological gravitational wave background.

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Testing the early universe with anisotropies of the gravitational wave background

Cited by 26 publications

References 116 publications

Doppler boosting the stochastic gravitational wave background

Doppler boosting the stochastic gravitational wave background

Probing parity-odd bispectra with anisotropies of GW V modes

Kinematic anisotropies and pulsar timing arrays

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