Parity Violation of Gravitons in the CMB Bispectrum(Astrophysics and Cosmology)

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概要

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• We investigate the cosmic microwave background (CMB) bispectra of the intensity (temperature) and polarization modes induced by the graviton non-Gaussianities, which arise from the parity-conserving and parity-violating Weyl cubic terms with time-dependent coupling. By considering the time-dependent coupling, we find that even in the exact de Sitter space time, the parity violation still appears in the three-point function of the primordial gravitational waves and could become large. Through the estimation of the CMB bispectra, we demonstrate that the signals generated from the parity-conserving and parity-violating terms appear in completely different configurations of multipoles. For example, the parity-conserving non-Gaussianity induces the nonzero CMB temperature bispectrum in the configuration with Σ_<n=1>^3l_n=even and, while due to the parity-violating non-Gaussianity, the CMB temperature bispectrum also appears for Σ_<n=1>^3l_n=odd. This signal is just good evidence of the parity violation in the non-Gaussianity of primordial gravitational waves. We find that the shape of this non-Gaussianity is similar to the so-called equilateral one and the amplitudes of these spectra at large scale are roughly estimated as |b_<lll>|〜l^<-4>×3.2×10^<-2>(GeV/Λ)^2 (r/0.1)^4, where Λ is an energy scale that sets the magnitude of the Weyl cubic terms (higher derivative corrections) and r is a tensor-to-scalar ratio. Taking the limit for the nonlinearity parameter of the equilateral type as f_<NL>^<eq><300, we can obtain a bound as Λ&gsum;3×10^6GeV, assuming r=0.1.

• 2011-11-25

著者

• SHIRAISHI Maresuke

  Department of Physics and Astrophysics, Nagoya University

• NITTA Daisuke

  Department of Physics and Astrophysics, Nagoya University

• YOKOYAMA Shuichiro

  Department of Physics and Astrophysics, Nagoya University

• Nitta Daisuke

  Department Of Physics And Astrophysics Nagoya University

• Yokoyama Shuichiro

  Department Of Physics And Astrophysics Nagoya University

• Shiraishi Maresuke

  Department Of Physics And Astrophysics Nagoya University

関連論文

• CMB Bispectrum from Primordial Scalar, Vector and Tensor Non-Gaussianities(Astrophysics and Cosmology)
• Use of δN Formalism : Difficulty of Generating Large Local-Type Non-Gaussianity during Inflation(Chapter II: Cosmological perturbations,Cosmology-The Next Generation-)
• CMB Bispectrum from Primordial Scalar, Vector and Tensor Non-Gaussianities
• Parity Violation of Gravitons in the CMB Bispectrum(Astrophysics and Cosmology)
• Violation of the Rotational Invariance in the CMB Bispectrum(Astrophysics and Cosmology)
• A-33: A New Analytic Formula for the Spectrum of Inflationary Curvature Perturbations(Part II: Poster Contributions, The Next Chapter in Einstein's Legacy)

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