Generation of circular polarization in CMB radiation via nonlinear photon-photon interaction

Sadegh, Mahdi; Mohammadi, Rohoollah; Motie, Iman

doi:10.1103/physrevd.97.023023

Cited by 21 publications

(33 citation statements)

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“…That work builds upon a re-calculation [21], obtained with the TAM formalism [22,23], of circular polarization induced by photon-photon scattering, in Ref. [7], which itself extends several earlier analyses [2][3][4]6] of this effect. Note that the circular polarization induced through the photon-photon scattering is much larger than that induced through the photon-graviton scattering [20].…”

mentioning

confidence: 52%

“…This Thomson scattering does not, however, induce circular polarization. Recent work has shown that circular polarization can be generated, from primordial perturbations through post-recombination photon-photon scattering [2][3][4][5][6][7], at second order in the density-perturbation amplitude. Still, the mean value of the circular polarization, when averaged over the sky, is predicted to be zero.…”

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confidence: 99%

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Chiral Photons from Chiral Gravitational Waves

Inomata

Kamionkowski

2019

Phys. Rev. Lett.

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We show that a parity-breaking uniform (averaged over all directions on the sky) circular polarization of amplitude V00 ≃ 2.6×10 −17 ∆χ(r/0.06) can be induced by chiral gravitational-wave (GW) background with tensor-to-scalar ratio r and chirality parameter ∆χ (which is ±1 for a maximally chiral background). We also show, however, that a uniform circular polarization can arise from a realization of a non-chiral GW background that spontaneously breaks parity. The magnitude of this polarization is drawn from a distribution of root-variance V 2 00 ≃ 1.5 × 10 −18 (r/0.06) 1/2 implying that the chirality parameter must be ∆χ 0.12(r/0.06) −1/2 to establish that the GW background is chiral. Although these values are too small to be detected by any experiment in the foreseeable future, the calculation is a proof of principle that cosmological parity breaking in the form of a chiral gravitational-wave background can be imprinted in the chirality of the photons in the cosmic microwave background. It also illustrates how a seemingly parity-breaking cosmological signal can arise from parity-conserving physics.

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confidence: 52%

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confidence: 99%

Chiral Photons from Chiral Gravitational Waves

Inomata

Kamionkowski

2019

Phys. Rev. Lett.

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“…In the framework of cosmological perturbation theory, this arises as a second order effect, similar to the production of V due to photon-photon scattering [5,[7][8][9][10]14]. The relevant scattering process in this case is gravitonphoton scattering [32] .…”

Section: Primordial V-modes In the Cmbmentioning

confidence: 99%

“…For this reason, the primordial V is expected to vanish, and the focus of much work to date (e.g. [3][4][5][6][7][8][9][10][11][12]) has been on 'conventional' sources of circular polarization, e.g. Faraday conversion [3], which in many cases leads to a negligible large-scale CMB signal [5] ( 10 −14 K).…”

Section: Introductionmentioning

confidence: 99%

Primordial circular polarization in the cosmic microwave background

Alexander

McDonough

2019

Physics Letters B

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Circular ("V-mode") polarization is expected to be vanishing in the CMB, since it is not produced in Thomson scattering. However, considering that the conventional CMB anisotropies are generated via an early universe mechanism such as inflation or a bouncing scenario, it is possible that circular polarization could be primordially produced and survive to the surface of last scattering. We study this in detail, and find a large class of inflationary models that produce a nearly scale invariant spectrum of scalar V-mode anisotropies. We study the inflationary production and subsequent evolution via the Boltzmann hierarchy, and show that V-mode polarization present in the CMB is suppressed by a factor of at least 10 10 20 relative to the primordial V , consistent with expectation of negligible V-mode polarization from inflation. We consider alternative possibilities for sourcing V primordially, such as the V-mode polarization induced by circularly polarized primordial gravitational waves, or producing V after inflation, via new interactions at recombination.

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“…There are a number of possible standard-model sources of the cosmic birefringence needed for Faraday conversion, including, for example, spin-polarization of hydrogen atoms induced by an anisotropic CMB background [24]. Still, the most significant source is photon-photon interactions [24,[31][32][33][34][35], which is the mechanism we consider here. In this case, the required birefringence is provided by the CMB anisotropies seen by the CMB photon as it propagates from the surface of last scatter.…”

Section: Introductionmentioning

confidence: 99%

Circular polarization of the cosmic microwave background from vector and tensor perturbations

Inomata

Kamionkowski

2019

Phys. Rev. D

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Circular polarization of the cosmic microwave background (CMB) can be induced by Faraday conversion of the primordial linearly polarized radiation as it propagates through a birefringent medium. Recent work has shown that the dominant source of birefringence from primordial density perturbations is the anisotropic background CMB. Here we extend prior work to allow for the additional birefringence that may arise from primordial vector and tensor perturbations. We derive the formulas for the power spectrum of the induced circular polarization and apply those to the standard cosmology. We find the root-variance of the induced circular polarization to be V 2 ∼ 3 × 10 −14 for scalar perturbations and V 2 ∼ 7 × 10 −18 (r/0.06) for tensor perturbations with a tensor-to-scalar ratio r.

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Generation of circular polarization in CMB radiation via nonlinear photon-photon interaction

Cited by 21 publications

References 50 publications

Chiral Photons from Chiral Gravitational Waves

Chiral Photons from Chiral Gravitational Waves

Primordial circular polarization in the cosmic microwave background

Circular polarization of the cosmic microwave background from vector and tensor perturbations

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