Analytic description of the damping of gravitational waves by free streaming neutrinos

Stefanek, Ben A.; Repko, Wayne W.

doi:10.1103/physrevd.88.083536

Cited by 39 publications

(44 citation statements)

References 14 publications

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“…Now, it is a well established result that transverse gravitational waves are not absorbed by non-collisional massive media [30][31][32][33]. Damping is indeed only possible in the presence of viscosity [10,34,35], or when a medium of massless particles is considered [36][37][38]). Then, having in mind that the presence of longitudinal modes could imply the gravitational analog of Landau damping, we adopt a kinetic theory approach and we analyze the interaction of scalar waves with a collisionless particle distribution.…”

Section: Introductionmentioning

confidence: 99%

Gravitational Landau damping for massive scalar modes

2020

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We establish the possibility of Landau damping for gravitational scalar waves which propagate in a non-collisional gas of particles. In particular, under the hypothesis of homogeneity and isotropy, we describe the medium at the equilibrium with a Jüttner–Maxwell distribution, and we analytically determine the damping rate from the Vlasov equation. We find that damping occurs only if the phase velocity of the wave is subluminal throughout the propagation within the medium. Finally, we investigate relativistic media in cosmological settings by adopting numerical techniques.

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Section: Introductionmentioning

confidence: 99%

Gravitational Landau damping for massive scalar modes

2020

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“…Detailed studies of the effects of the SM neutrinos on the tensor modes (the B-and E-modes) of the CMB were performed in [44,45], which found an O(10)% damping of the correlation functions of the tensor modes at long wavelengths, rising to an O(35)% damping at short wavelengths. Analytic results for the damping were subsequently obtained in [59,60]. The corrections to the spectrum that arise from the presence of a free streaming DR component were considered in [61].…”

Section: Distinguishing Between Free and Scattering Dr Via Tensor mentioning

confidence: 99%

“…Expressions for χ SM (y dec ) and χ 0 (y dec ) at small Q were obtained in [60], Here y dec is the value of y at photon decoupling, given by y dec = 3.31. Note that the regime of validity of these expansions is limited to small Q, and they are expected to break down at Q ∼ 1.…”

Section: Distinguishing Between Free and Scattering Dr Via Tensor mentioning

confidence: 99%

Hidden dark matter sector, dark radiation, and the CMB

et al. 2015

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We consider theories where dark matter is composed of a thermal relic of weak scale mass, whose couplings to the Standard Model (SM) are however too small to give rise to the observed abundance. Instead, the abundance is set by annihilation to light hidden sector states that carry no charges under the SM gauge interactions. In such a scenario the constraints from direct and indirect detection, and from collider searches for dark matter, can easily be satisfied. The masses of such light hidden states can be protected by symmetry if they are Nambu-Goldstone bosons, fermions, or gauge bosons. These states can then contribute to the cosmic energy density as dark radiation, leading to observable signals in the cosmic microwave background (CMB). Furthermore, depending on whether or not the light hidden sector states self-interact, the fraction of the total energy density that free-streams is either decreased or increased, leading to characteristic effects on both the scalar and tensor components of the CMB anisotropy that allows these two cases to be distinguished. The magnitude of these signals depends on the number of light degrees of freedom in the hidden sector, and on the temperature at which it kinetically decouples from the SM. We consider a simple model that realizes this scenario, based on a framework in which the SM and hidden sector are initially in thermal equilibrium through the Higgs portal, and show that the resulting signals are compatible with recent Planck results, while large enough to be detected in upcoming experiments such as CMBPol and CMB Stage-IV. Invisible decays of the Higgs into hidden sector states at colliders can offer a complementary probe of this model.

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“…This result is valid only if the collision frequency in the matter 1 is much greater than the frequency of the GW. A well-known effect given by decoupled relativistic neutrinos on the CMB angular power-spectrum is the damping due to their anisotropic stress of the amplitude of the GW spectrum by 35% [30] (see also [31][32][33][34][35][36]). Such a damping becomes quite large in the frequency region between 10 −16 Hz and 10 −10 Hz [30][31][32][33][34][35][36].…”

Section: Introductionmentioning

confidence: 99%

Non-Markovian open quantum system approach to the early universe: I. Damping of gravitational waves by matter

Zarei,

Bartolo,

Bertacca

et al. 2021

Preprint

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By revising the application of the open quantum system approach to the early universe and extending it to the conditions beyond the Markovian approximation, we obtain a new non-Markovian quantum Boltzmann equation. Throughout the paper, we also develop an extension of the quantum Boltzmann equation to describe the processes that are irreversible at the macroscopic level. This new kinetic equation is, in principle, applicable to a wide variety of processes in the early universe. For instance, using this equation one can accurately study the microscopic influence of a cosmic environment on a system of cosmic background photons or stochastic gravitational waves. In this paper, we apply the non-Markovian quantum Boltzmann equation to study the damping of gravitational waves propagating in a medium consisting of decoupled ultra-relativistic neutrinos. For such a system, we study the time evolution of the intensity and the polarization of the gravitational waves. It is shown that, in contrast to intensity and linear polarization which are damped, the circular polarization (V-mode) of the gravitational wave (if present) is amplified by propagating through such a medium.

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Analytic description of the damping of gravitational waves by free streaming neutrinos

Cited by 39 publications

References 14 publications

Gravitational Landau damping for massive scalar modes

Gravitational Landau damping for massive scalar modes

Hidden dark matter sector, dark radiation, and the CMB

Non-Markovian open quantum system approach to the early universe: I. Damping of gravitational waves by matter

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