Black hole superradiance in dynamical Chern-Simons gravity

Alexander, Stephon; Gabadadze, Gregory; Jenks, Leah; Yunes, Nicolás

doi:10.1103/physrevd.107.084016

Cited by 11 publications

(1 citation statement)

References 84 publications

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“…Moreover, dCS gravity can also arise from spontaneous and dynamical symmetry breaking [63][64][65]. Outside of inflation, dCS gravity can cause alterations to bodies orbiting Earth [66], modifications to gravitational waves from compact binary coalescences [67][68][69][70][71][72][73], and new structures to form around black holes [74,75].…”

Section: Introductionmentioning

confidence: 99%

Parity-violating trispectrum from Chern-Simons gravity

Creque-Sarbinowski,

Alexander,

Kamionkowski

et al. 2023

J. Cosmol. Astropart. Phys.

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A potential source for parity violation in the Universe is inflation. The simplest inflationary models have two fields: the inflaton and graviton, and the lowest-order parity-violating coupling between them is dynamical Chern-Simons (dCS) gravity with a decay constant f. Here, we show that dCS imprints a parity-violating signal in primordial scalar perturbations. Specifically, we find that, after dCS amplifies one graviton helicity due to a tachyonic instability, the graviton-mediated correlation between two pairs of scalars develops a parity-odd component. This correlation, the primordial scalar trispectrum, is then transferred to the corresponding curvature correlator and thus is imprinted in both large-scale structure (LSS) and the cosmic microwave background (CMB). We find that the parity-odd piece has roughly the same amplitude as its parity-even counterpart, scaled linearly by the degree of gravitational circular polarization Πcirc ∼ √ε[h 2/(M Pl f)] ≤ 1, with ε the slow-roll parameter, H the inflationary Hubble scale, and the upper bound saturated for purely circularly-polarized gravitons. We also find that, in the collapsed limit, the ratio of the two trispectra contains direct information about the graviton's spin. In models beyond standard inflationary dCS, e.g. those with multiple scalar fields or superluminal scalar sound speed, there can be a large enhancement factor F ≳ 106 to the trispectrum. We find that an LSS survey that contains N modes linear modes would place an nσ constraint on Πcirc r of ∼ 0.04 (n/3)(106/F)(106/N modes)1/2 from the parity-odd galaxy trispectrum, for tensor-to-scalar ratio r. We also forecast for several spectroscopic and 21-cm surveys. This constraint implies that, for high-scale single-field inflation parameters, LSS can probe very large dCS decay constants f ≲ 4 × 109 GeV(3/n)(F/106)(N modes/106)1/2. Our result is the first example of a massless particle yielding a parity-odd scalar trispectrum through spin-exchange.

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Section: Introductionmentioning

confidence: 99%

Parity-violating trispectrum from Chern-Simons gravity

Creque-Sarbinowski,

Alexander,

Kamionkowski

et al. 2023

J. Cosmol. Astropart. Phys.

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Superradiance of rotating black holes surrounded by dark matter

Liu,

Hu,

Sui

et al. 2024

Physics of the Dark Universe

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Exact Solution for Rotating Black Holes in Parity-Violating Gravity

Tahara,

Takahashi,

Minamitsuji

et al. 2024

Progress of Theoretical and Experimental Physics

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It has recently been pointed out that one can construct invertible conformal transformations with a parity-violating conformal factor, which can be employed to generate a novel class of parity-violating ghost-free metric theories from general relativity. We obtain exact solutions for rotating black holes in such theories by performing the conformal transformation on the Kerr solution in general relativity, which we dub conformal Kerr solutions. We explore the geodesic motion of a test particle in the conformal Kerr spacetime. While null geodesics remain the same as those in the Kerr spacetime, timelike geodesics exhibit interesting differences due to an effective external force caused by the parity-violating conformal factor.

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Black hole superradiance in dynamical Chern-Simons gravity

Cited by 11 publications

References 84 publications

Parity-violating trispectrum from Chern-Simons gravity

Parity-violating trispectrum from Chern-Simons gravity

Superradiance of rotating black holes surrounded by dark matter

Exact Solution for Rotating Black Holes in Parity-Violating Gravity

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