Enhancing gravitational wave anisotropies with peaked scalar sources

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

doi:10.1088/1475-7516/2023/01/018

Cited by 16 publications

(7 citation statements)

References 163 publications

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“…In a different direction, it would also interesting to fully explore how GW background anisotropies (see, e.g., Ref. [318][319][320]) might help in gathering evidence for the presence of PBHs [268,269,321,322] and, perhaps, even the presence of primordial non-Gaussianity [135,323,324]. Moreover, as discussed in the context of MHz GW detectors by Ref.…”

Section: Discussionmentioning

confidence: 99%

Gravitational wave constraints on the primordial black hole dominated early universe

Domènech

Lin

Sasaki

2021

J. Cosmol. Astropart. Phys.

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We calculate the gravitational waves (GWs) induced by the density fluctuations due to the inhomogeneous distribution of primordial black holes (PBHs) in the case where PBHs eventually dominate and reheat the universe by Hawking evaporation. The initial PBH density fluctuations are isocurvature in nature. We find that most of the induced GWs are generated right after evaporation, when the universe transits from the PBH dominated era to the radiation dominated era and the curvature perturbation starts to oscillate wildly. The strongest constraint on the amount of the produced GWs comes from the big bang nucleosynthesis (BBN). We improve previous constraints on the PBH fraction and find that it cannot exceed 10-4. Furthermore, this maximum fraction decreases as the mass increases and reaches 10-12 for MPBH∼ 5×108 g, which is the largest mass allowed by the BBN constraint on the reheating temperature. Considering that PBH may cluster above a given clustering scale, we also derive a lower bound on the scale of clustering. Interestingly, the GW spectrum for MPBH∼ 104 -108 g enters the observational window of LIGO and DECIGO and could be tested in the future. Although we focus on the PBH dominated early universe in this paper, our methodology is applicable to any model with early isocurvature perturbation.

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Section: Discussionmentioning

confidence: 99%

Gravitational wave constraints on the primordial black hole dominated early universe

Domènech

Lin

Sasaki

2021

J. Cosmol. Astropart. Phys.

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“…The initial condition term for the GW evolution appearing in Eq. ( 6) can be computed with the methods discussed in [71] and is different from the radiation domination relation Γ I ¼ −Φ=2. In fact, for a general w and assuming adiabatic primordial perturbations, we find (see Appendix B)…”

Section: Sgwb Anisotropies For Adiabatic Primordial Fluctuationsmentioning

confidence: 99%

New universal property of cosmological gravitational wave anisotropies

et al. 2023

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The anisotropies of the stochastic gravitational wave background, as produced in the early phases of cosmological evolution, can act as a key probe of the primordial universe particle content. We point out a new universal property of gravitational wave anisotropies of cosmological origin: for adiabatic initial conditions, their angular power spectrum is insensitive to the equation of state of the cosmic fluid driving the expansion before big bang nucleosynthesis. Any deviation from this universal behavior points to the presence of nonadiabatic sources of primordial fluctuations. Such scenarios can be tested by gravitational wave detectors operating at a frequency range which is fully complementary to cosmic microwave background (CMB) experiments. In this work, we prove this general result, and we illustrate its consequences for a representative realization of initial conditions based on the curvaton scenario. In the case of the simplest curvaton setup, we also find a significant cross-correlation between gravitational wave anisotropies and the CMB temperature fluctuations. There is a fourfold enhancement vis-à-vis the purely adiabatic scenario. We discuss the implications of our findings for identifying the origin of the (cosmological) gravitational wave background when, as is often the case, this cannot be determined solely on the basis of its spectral shape.

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“…The resulting slope n I of the intensity spectrum is equal to the parameter γ at small frequencies, and to −δ at larger frequencies. For a large values of σ, at intermediate frequencies the quantity α I can increase by several orders of magnitude, enhancing the quadrupolar kinematic anisotropies to a size comparable to the dipolar ones (see [101] for related effects explored for the case of interferometers). We represent in Fig 2, left panel, an example to visually demonstrate such behaviour for the slope parameters.…”

Section: Examples Of Sgwb Frequency Dependencementioning

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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Enhancing gravitational wave anisotropies with peaked scalar sources

Cited by 16 publications

References 163 publications

Gravitational wave constraints on the primordial black hole dominated early universe

Gravitational wave constraints on the primordial black hole dominated early universe

New universal property of cosmological gravitational wave anisotropies

Kinematic anisotropies and pulsar timing arrays

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