Atsuhisa Ota
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The organizations/institutes from the scholar's latest article
Previous Organizations / Institutes
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Research Subjects
Atsuhisa Ota has a total of 7 co-authors. Here are the top co-authors by number of shared publications:
- Andrea Ravenni
Dipartimento di Fisica e Astronomia "G. Galilei" Università degli Studi di Padova via Mar- zolo 8 I-35131 Padova Italy
2 shared publications - Keisuke Inomata
Johns Hopkins University
2 shared publications Nicola Bartolo
Dipartimento di Fisica e Astronomia "G. Galilei" Università degli Studi di Padova via Marzolo 8 I-35131 Padova Italy
2 shared publications- Taku Haga
Department of Physics Tokyo Institute of Technology 152-8551 Tokyo Japan
2 shared publications - Masaru Hongo
Niigata University
1 shared publication - Suro Kim
Department of Physics Kobe University 657-8501 Kobe Japan
1 shared publication
Latest Publications
- Open Access
CMB spectroscopy at third-order in cosmological perturbations
Early energy injection to the Cosmic Microwave Background (CMB) from dissipation of acoustic waves generates deviations from the blackbody spectrum not only at second-order but also at third-order in cosmological perturbations. We compute this new spectral distortion $\mathcal \kappa$ based on third-order cosmological perturbation theory and show that $\kappa$ arises as a result of mode coupling between spectral distortions and temperature perturbations. The ensemble average of $\kappa$ can be directly sourced by (integrated) primordial non-Gaussianity. In particular, we roughly estimate the signal as $\kappa=f^{\rm loc.}_{\rm NL}\times \mathcal O(10^{-18})$ for local type scale-independent non-Gaussianity. The signal is incredibly tiny; however, we argue that it carries a specific frequency dependence different from other types of CMB spectral distortions. Also, it should be noticed that $\kappa$ is sensitive to extremely squeezed shapes of primordial bispectra that cannot be constrained by the CMB anisotropies. Finally, we comment on other possible applications of our results.Open AccessCMB spectroscopy at third-order in cosmological perturbations
Early energy injection to the Cosmic Microwave Background (CMB) from dissipation of acoustic waves generates deviations from the blackbody spectrum not only at second-order but also at third-order in cosmological perturbations. We compute this new spectral distortion $\mathcal \kappa$ based on third-order cosmological perturbation theory and show that $\kappa$ arises as a result of mode coupling between spectral distortions and temperature perturbations. The ensemble average of $\kappa$ can be directly sourced by (integrated) primordial non-Gaussianity. In particular, we roughly estimate the signal as $\kappa=f^{\rm loc.}_{\rm NL}\times \mathcal O(10^{-18})$ for local type scale-independent non-Gaussianity. The signal is incredibly tiny; however, we argue that it carries a specific frequency dependence different from other types of CMB spectral distortions. Also, it should be noticed that $\kappa$ is sensitive to extremely squeezed shapes of primordial bispectra that cannot be constrained by the CMB anisotropies. Finally, we comment on other possible applications of our results. - 13 August 2019
- Published by American Physical Society (APS) in Physical Review D
- Vol. 100 (4) , 043521
CMB spectroscopy at third-order in cosmological perturbations
Early energy injection to the Cosmic Microwave Background (CMB) from dissipation of acoustic waves generates deviations from the blackbody spectrum not only at second-order but also at third-order in cosmological perturbations. We compute this new spectral distortion based on third-order cosmological perturbation theory and show that arises as a result of mode coupling between spectral distortions and temperature perturbations. The ensemble average of can be directly sourced by (integrated) primordial non-Gaussianity. In particular, we roughly estimate the signal as for local type scale-independent non-Gaussianity. The signal is incredibly tiny; however, we argue that it carries a specific frequency dependence different from other types of CMB spectral distortions. Also, it should be noticed that is sensitive to extremely squeezed shapes of primordial bispectra that cannot be constrained by the CMB anisotropies. Finally, we comment on other possible applications of our results.- 13 August 2019
- Published by American Physical Society (APS) in Physical Review D
- Vol. 100 (4) , 043521
CMB spectroscopy at third-order in cosmological perturbations
Early energy injection to the Cosmic Microwave Background (CMB) from dissipation of acoustic waves generates deviations from the blackbody spectrum not only at second-order but also at third-order in cosmological perturbations. We compute this new spectral distortion based on third-order cosmological perturbation theory and show that arises as a result of mode coupling between spectral distortions and temperature perturbations. The ensemble average of can be directly sourced by (integrated) primordial non-Gaussianity. In particular, we roughly estimate the signal as for local type scale-independent non-Gaussianity. The signal is incredibly tiny; however, we argue that it carries a specific frequency dependence different from other types of CMB spectral distortions. Also, it should be noticed that is sensitive to extremely squeezed shapes of primordial bispectra that cannot be constrained by the CMB anisotropies. Finally, we comment on other possible applications of our results.- Open Access
Exploring compensated isocurvature perturbations with CMB spectral distortion anisotropies
We develop a linear perturbation theory for the spectral $y$-distortions of the cosmic microwave background (CMB). The $y$-distortions generated during the recombination epoch are usually negligible because the energy transfer due to the Compton scattering is strongly suppressed at that time, but they can be significant if there is a considerable amount of compensated isocurvature perturbation (CIP), which is not tightly constrained from the present CMB observations. The linear $y$-distortions explicitly depend on the baryon density fluctuations, therefore $y$ anisotropies can completely resolve the degeneracy between the baryon isocurvature perturbations and the cold dark matter ones. This novel method is free from lensing contaminations that can affect the previous approach to the CIPs based on the nonlinear modulation of the CMB anisotropies. We compute the cross correlation functions of the $y$-distortions with the CMB temperature and the $E$ mode polarization anisotropies. They are sensitive to the correlated CIPs parameterized by $f'\equiv\mathcal P_{\rm CIP\zeta}/\mathcal P_{\zeta \zeta}$ with $\mathcal P_{\zeta \zeta}$ and $\mathcal P_{\rm CIP\zeta}$ being the auto correlation of the adiabatic perturbations and the cross correlation between them and the CIPs. We investigate how well the $y$ anisotropies will constrain $f'$ in future observations such as those provided by a PIXIE-like and a PRISM-like survey, LiteBIRD and a cosmic variance limited (CVL) survey, taking into account the degradation in constraining power due to the presence of Sunyaev Zel'dovich effect from galaxy clusters. For example, our forecasts show that it is possible to achieve an upper limit of $f'< 2 \times 10^{5}$ at 68% C.L. with LiteBIRD, and $f'<2\times 10^{4}$ with CVL observations.Open AccessExploring compensated isocurvature perturbations with CMB spectral distortion anisotropies
We develop a linear perturbation theory for the spectral $y$-distortions of the cosmic microwave background (CMB). The $y$-distortions generated during the recombination epoch are usually negligible because the energy transfer due to the Compton scattering is strongly suppressed at that time, but they can be significant if there is a considerable amount of compensated isocurvature perturbation (CIP), which is not tightly constrained from the present CMB observations. The linear $y$-distortions explicitly depend on the baryon density fluctuations, therefore $y$ anisotropies can completely resolve the degeneracy between the baryon isocurvature perturbations and the cold dark matter ones. This novel method is free from lensing contaminations that can affect the previous approach to the CIPs based on the nonlinear modulation of the CMB anisotropies. We compute the cross correlation functions of the $y$-distortions with the CMB temperature and the $E$ mode polarization anisotropies. They are sensitive to the correlated CIPs parameterized by $f'\equiv\mathcal P_{\rm CIP\zeta}/\mathcal P_{\zeta \zeta}$ with $\mathcal P_{\zeta \zeta}$ and $\mathcal P_{\rm CIP\zeta}$ being the auto correlation of the adiabatic perturbations and the cross correlation between them and the CIPs. We investigate how well the $y$ anisotropies will constrain $f'$ in future observations such as those provided by a PIXIE-like and a PRISM-like survey, LiteBIRD and a cosmic variance limited (CVL) survey, taking into account the degradation in constraining power due to the presence of Sunyaev Zel'dovich effect from galaxy clusters. For example, our forecasts show that it is possible to achieve an upper limit of $f'< 2 \times 10^{5}$ at 68% C.L. with LiteBIRD, and $f'<2\times 10^{4}$ with CVL observations. - Open Access
Effective field theory of time-translational symmetry breaking in nonequilibrium open system
We develop the effective field theoretical (EFT) approach to time-translational symmetry breaking of nonequilibrium open systems based on the Schwinger-Keldysh formalism. In the Schwinger-Keldysh formalism, all the symmetries of the microscopic Lagrangian are doubled essentially because the dynamical fields are doubled to describe the time-evolution along the closed-time-path. The effective Lagrangian for open systems are then obtained by coarse-graining the microscopic Schwinger-Keldysh Lagrangian. As a consequence of coarse-graining procedure, there appear the noise and dissipation effects, which explicitly break the doubled time-translational symmetries into a diagonal one. We therefore need to incorporate this symmetry structure to construct the EFT for Nambu-Goldstone bosons in symmetry broken phases of open systems. Based on this observation together with the consistency of the Schwinger-Keldysh action, we construct and study the general EFT for time-translational symmetry breaking in particular, having in mind applications to synchronization, time crystal, and cosmic inflation.
Open AccessEffective field theory of time-translational symmetry breaking in nonequilibrium open system
We develop the effective field theoretical (EFT) approach to time-translational symmetry breaking of nonequilibrium open systems based on the Schwinger-Keldysh formalism. In the Schwinger-Keldysh formalism, all the symmetries of the microscopic Lagrangian are doubled essentially because the dynamical fields are doubled to describe the time-evolution along the closed-time-path. The effective Lagrangian for open systems are then obtained by coarse-graining the microscopic Schwinger-Keldysh Lagrangian. As a consequence of coarse-graining procedure, there appear the noise and dissipation effects, which explicitly break the doubled time-translational symmetries into a diagonal one. We therefore need to incorporate this symmetry structure to construct the EFT for Nambu-Goldstone bosons in symmetry broken phases of open systems. Based on this observation together with the consistency of the Schwinger-Keldysh action, we construct and study the general EFT for time-translational symmetry breaking in particular, having in mind applications to synchronization, time crystal, and cosmic inflation.
- 1 August 2018
- Published by IOP Publishing in Journal of Cosmology and Astroparticle Physics
- Vol. 2018 (08) , 036
Exploring compensated isocurvature perturbations with CMB spectral distortion anisotropies
We develop a linear perturbation theory for the spectral y-distortions of the cosmic microwave background (CMB). The y-distortions generated during the recombination epoch are usually negligible because the energy transfer due to the Compton scattering is strongly suppressed at that time, but they can be significant if there is a considerable amount of compensated isocurvature perturbation (CIP), which is not tightly constrained from the present CMB observations. The linear y-distortions explicitly depend on the baryon density fluctuations, therefore y anisotropies can completely resolve the degeneracy between the baryon isocurvature perturbations and the cold dark matter ones. This novel method is free from lensing contaminations that can affect the previous approach to the CIPs based on the nonlinear modulation of the CMB anisotropies. We compute the cross correlation functions of the y-distortions with the CMB temperature and the E mode polarization anisotropies. They are sensitive to the correlated CIPs parameterized by f'≡CIPζ/ζ ζ with ζ ζ and CIPζ being the auto correlation of the adiabatic perturbations and the cross correlation between them and the CIPs. We investigate how well the y anisotropies will constrain f' in future observations such as those provided by a PIXIE-like and a PRISM-like survey, LiteBIRD and a cosmic variance limited (CVL) survey, taking into account the degradation in constraining power due to the presence of Sunyaev Zel'dovich effect from galaxy clusters. For example, our forecasts show that it is possible to achieve an upper limit of {f'< 2 × 105} at 68% C.L. with LiteBIRD, and f'4 with CVL observations.
- 1 August 2018
- Published by IOP Publishing in Journal of Cosmology and Astroparticle Physics
- Vol. 2018 (08) , 036
Exploring compensated isocurvature perturbations with CMB spectral distortion anisotropies
We develop a linear perturbation theory for the spectral y-distortions of the cosmic microwave background (CMB). The y-distortions generated during the recombination epoch are usually negligible because the energy transfer due to the Compton scattering is strongly suppressed at that time, but they can be significant if there is a considerable amount of compensated isocurvature perturbation (CIP), which is not tightly constrained from the present CMB observations. The linear y-distortions explicitly depend on the baryon density fluctuations, therefore y anisotropies can completely resolve the degeneracy between the baryon isocurvature perturbations and the cold dark matter ones. This novel method is free from lensing contaminations that can affect the previous approach to the CIPs based on the nonlinear modulation of the CMB anisotropies. We compute the cross correlation functions of the y-distortions with the CMB temperature and the E mode polarization anisotropies. They are sensitive to the correlated CIPs parameterized by f'≡CIPζ/ζ ζ with ζ ζ and CIPζ being the auto correlation of the adiabatic perturbations and the cross correlation between them and the CIPs. We investigate how well the y anisotropies will constrain f' in future observations such as those provided by a PIXIE-like and a PRISM-like survey, LiteBIRD and a cosmic variance limited (CVL) survey, taking into account the degradation in constraining power due to the presence of Sunyaev Zel'dovich effect from galaxy clusters. For example, our forecasts show that it is possible to achieve an upper limit of {f'< 2 × 105} at 68% C.L. with LiteBIRD, and f'4 with CVL observations.