Analytic spectra of CMB anisotropies and polarization generated by relic gravitational waves with modification due to neutrino free-streaming

Xia, Tianyang; Zhang, Y.

doi:10.1103/physrevd.78.123005

Cited by 38 publications

(22 citation statements)

References 59 publications

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“…Following Baumann et al (2016), φgr,ν can be analytically studied by a perturbation approach, whose earlier version was orginally developed for probing the impact of neutrino free-streaming on tensor modes (e.g. Weinberg 2004;Dicus & Repko 2005;Watanabe & Komatsu 2006;Miao & Zhang 2007;Xia & Zhang 2008). Accurate to O(Rν ), the two potential are written as…”

Section: Appendix B: φGrγmentioning

confidence: 99%

Cosmic microwave background acoustic peak locations

Pan

Knox

Mulroe

et al. 2016

Mon. Not. R. Astron. Soc.

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The Planck collaboration has measured the temperature and polarization of the cosmic microwave background well enough to determine the locations of eight peaks in the temperature (TT) power spectrum, five peaks in the polarization (EE) power spectrum and twelve extrema in the cross (TE) power spectrum. The relative locations of these extrema give a striking, and beautiful, demonstration of what we expect from acoustic oscillations in the plasma; e.g., that EE peaks fall half way between TT peaks. We expect this because the temperature map is predominantly sourced by temperature variations in the last scattering surface, while the polarization map is predominantly sourced by gradients in the velocity field, and the harmonic oscillations have temperature and velocity 90 degrees out of phase. However, there are large differences in expectations for extrema locations from simple analytic models vs. numerical calculations. Here we quantitatively explore the origin of these differences in gravitational potential transients, neutrino free-streaming, the breakdown of tight coupling, the shape of the primordial power spectrum, details of the geometric projection from three to two dimensions, and the thickness of the last scattering surface. We also compare the peak locations determined from Planck measurements to expectations under the ΛCDM model. Taking into account how the peak locations were determined, we find them to be in agreement.

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Section: Appendix B: φGrγmentioning

confidence: 99%

Cosmic microwave background acoustic peak locations

Pan

Knox

Mulroe

et al. 2016

Mon. Not. R. Astron. Soc.

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“…However, GWs are sourced by the anisotropic stress part of the energy-momentum tensor of matter, so that the above assumption is well motivated only when anisotropic stress can be neglected. It is already known that the anisotropic stress of free streaming neutrinos acts as an effective viscosity, absorbing GWs in the low-frequency region, thus resulting in a damping of the B-modes of CMB [12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

A possible signature of cosmic neutrino decoupling in the nHz region of the spectrum of primordial gravitational waves

Lattanzi¹,

Benini²,

Montani³

2010

Class. Quantum Grav.

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. A possible signature of cosmic neutrino decoupling in the nHz region of the spectrum of primordial gravitational waves. Classical and Quantum Gravity, IOP Publishing, 2010, 27 (19) Abstract. In this paper we study the effect of cosmic neutrino decoupling on the spectrum of cosmological gravitational waves (GWs). At temperatures T 1 MeV, neutrinos constitute a perfect fluid and do not hinder GW propagation, while for T 1 MeV they free-stream and have an effective viscosity that damps cosmological GWs by a constant amount. In the intermediate regime, corresponding to neutrino decoupling, the damping is frequency-dependent. GWs entering the horizon during neutrino decoupling have a frequency f ∼ 1 nHz, corresponding to a frequency region that will be probed by Pulsar Timing Arrays (PTAs). In particular, we show how neutrino decoupling induces a spectral feature in the spectrum of cosmological GWs just below 1 nHz. We briefly discuss the conditions for a detection of this feature and conclude that it is unlikely to be observed by PTAs.

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“…(2.2). However, as was pointed out and studied in [72][73][74][75][76][77][78][79], non-zero anisotropic stresses will also alter the dynamics of tensor perturbations. For a fixed non-zero tensor-to-scalar ratio, they reduce the CMB B-mode polarization power spectrum beyond 200 as compared to the case without free-streaming neutrinos.…”

Section: An Example Of Z Decimentioning

confidence: 88%

Probing decoupling in dark sectors with the cosmic microwave background

Choi

Chiang

Loverde

2018

J. Cosmol. Astropart. Phys.

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The acoustic peaks in the angular power spectrum of cosmic microwave background (CMB) temperature and polarization anisotropies play an important role as a probe of the nature of new relativistic particles contributing to the radiation density in the early universe, parametrized by ∆N ef f . The amplitude and phase of the acoustic oscillations provide information about whether the extra species are free-streaming particles, like neutrinos, or tightly-coupled, like the photons, during eras probed by the CMB. On the other hand, some extensions of the Standard Model produce new relativistic particles that decouple from their own non-gravitational interactions after neutrinos, but prior to photons. We study the signature of new relativistic species that decouple during this intermediate epoch. We argue that the decoupling species will cause a scale-dependent change in the amplitude and phase shift of the acoustic oscillations, different from the usual constant shifts on small scales. For intermediate decoupling times, the phase and amplitude shifts depend not only on ∆N ef f but the redshift z dec,X at which the new species decoupled. For ∆N ef f > 0.334, a Stage IV CMB experiment could determine N ef f at the percent level and z dec,X at the ∼ 10% level. For smaller values, ∆N ef f ∼ 0.1, constraints on z dec,X weaken but remain ∼ 20 − 50% for z dec,X ∼ O(10 3 − 10 4 ). As an application, we study the contributions to ∆N ef f and determine the z dec,X values for simple implementations of the so-called N naturalness model.

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Analytic spectra of CMB anisotropies and polarization generated by relic gravitational waves with modification due to neutrino free-streaming

Cited by 38 publications

References 59 publications

Cosmic microwave background acoustic peak locations

Cosmic microwave background acoustic peak locations

A possible signature of cosmic neutrino decoupling in the nHz region of the spectrum of primordial gravitational waves

Probing decoupling in dark sectors with the cosmic microwave background

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