Obata Ippei 小幡一平

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小幡一平オバタイッペイ

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Researcher Number	50823621
Other IDs	https://orcid.org/0000-0001-9737-5631
Affiliation (Current)	2026: 大学共同利用機関法人高エネルギー加速器研究機構, 素粒子原子核研究所, 特任助教
Affiliation (based on the past Project Information) *help	2022 – 2024: 東京大学, カブリ数物連携宇宙研究機構, 特任研究員 2019: 東京大学, 宇宙線研究所, 特任研究員
Review Section/Research Field	Principal Investigator Basic Section 15010:Theoretical studies related to particle-, nuclear-, cosmic ray and astro-physics
Keywords	Principal Investigator 重力波干渉計 / 暗黒エネルギー / 標準模型 / 光子(ゲージ場) / 原始非ガウス性 / 暗黒物質 / 宇宙背景放射 / 光子（ゲージ場） / 原始重力波 / パルサータイミングアレイ / インフレーション / アクシオン / 宇宙論

Cosmological Research in Axion Physics: Phenomenology of Parity-Violation in Polarized PhotonPrincipal Investigator
- Principal Investigator
  
  小幡一平
- Project Period (FY)
  2021 – 2025
- Research Category
  
  Grant-in-Aid for Early-Career Scientists
- Review Section
  
  Basic Section 15010:Theoretical studies related to particle-, nuclear-, cosmic ray and astro-physics
- Research Institution
  The University of Tokyo

All 2025 2024 2023 2022 2019

All Journal Article Presentation

[Journal Article] Axionic defects in the CMB: birefringence and gravitational waves2024
- Author(s)
  Ricardo Z. Ferreira, Silvia Gasparotto, Takashi Hiramatsu, Ippei Obata, Oriol Pujolas
- Journal Title
  
  Journal of Cosmology and Astroparticle Physics（掲載決定）
  
  Volume: 未定
- Peer Reviewed / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702
[Journal Article] Can we explain cosmic birefringence without a new light field beyond Standard Model?2024
- Author(s)
  Yuichiro Nakai, Ryo Namba, Ippei Obata, Yu-Cheng Qiu, Ryo Saito
- Journal Title
  
  Journal of High Energy Physics
  
  Volume: 01 Issue: 1 Pages: 057-057
- DOI
  10.1007/jhep01(2024)057
- Peer Reviewed / Open Access / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702, KAKENHI-PLANNED-20H05859, KAKENHI-PLANNED-20H05860, KAKENHI-PROJECT-23K25868
[Journal Article] Constraining ultralight ALP dark matter in light of cosmic birefringence2024
- Author(s)
  Zhang Dongdong、Ferreira Elisa G. M.、Obata Ippei、Namikawa Toshiya
- Journal Title
  
  Physical Review D
  
  Volume: 110 Issue: 10 Pages: 103525-103525
- DOI
  10.1103/physrevd.110.103525
- Peer Reviewed / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-22K03682, KAKENHI-PROJECT-19K14702
[Journal Article] Parity-violating scalar trispectrum from a rolling axion during inflation2024
- Author(s)
  Tomohiro Fujita, Tomoaki Murata, Ippei Obata, Maresuke Shiraishi
- Journal Title
  
  Journal of Cosmology and Astroparticle Physics (掲載決定)
  
  Volume: 未定
- Peer Reviewed
- Data Source
  KAKENHI-PROJECT-19K14702
[Journal Article] Axion-gauge dynamics during inflation as the origin of pulsar timing array signals and primordial black holes2024
- Author(s)
  Unal Caner、Papageorgiou Alexandros、Obata Ippei
- Journal Title
  
  Physics Letters B
  
  Volume: 856 Pages: 1-6
- DOI
  10.1016/j.physletb.2024.138873
- Peer Reviewed / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702
[Journal Article] Cosmic birefringence tomography with polarized Sunyaev-Zel'dovich effect2023
- Author(s)
  Toshiya Namikawa, Ippei Obata
- Journal Title
  
  Physical Review D
  
  Volume: 108 Issue: 8 Pages: 083510-083510
- DOI
  10.1103/physrevd.108.083510
- Peer Reviewed
- Data Source
  KAKENHI-PROJECT-19K14702, KAKENHI-PROJECT-22K03682, KAKENHI-PLANNED-20H05859
[Journal Article] Stochastic effects on observation of ultralight bosonic dark matter2023
- Author(s)
  Hiromasa Nakatsuka, Soichiro Morisaki, Tomohiro Fujita, Jun'ya Kume, Yuta Michimura, Koji Nagano, Ippei Obata
- Journal Title
  
  Physical Review D
  
  Volume: 108 Issue: 9 Pages: 092010-092010
- DOI
  10.1103/physrevd.108.092010
- Peer Reviewed / Open Access / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702, KAKENHI-PROJECT-20H05639, KAKENHI-PLANNED-20H05854, KAKENHI-PLANNED-23H04893
[Journal Article] First results of axion dark matter search with DANCE2023
- Author(s)
  Yuka Oshima, Hiroki Fujimoto, Jun'ya Kume, Soichiro Morisaki, Koji Nagano, Tomohiro Fujita, Ippei Obata, Atsushi Nishizawa, Yuta Michimura, Masaki Ando
- Journal Title
  
  Physical Review D
  
  Volume: 108 Issue: 7 Pages: 072005-072005
- DOI
  10.1103/physrevd.108.072005
- Peer Reviewed / Open Access / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702, KAKENHI-PROJECT-22KJ1040, KAKENHI-PROJECT-22KJ1071, KAKENHI-PROJECT-23K03408, KAKENHI-PROJECT-23K03424, KAKENHI-PROJECT-20H05639, KAKENHI-PLANNED-20H05854, KAKENHI-PROJECT-23H00110, KAKENHI-PLANNED-23H04893
[Journal Article] Cosmic birefringence from monodromic axion dark energy2022
- Author(s)
  Silvia Gasparotto, Ippei Obata
- Journal Title
  
  JCAP
  
  Volume: 08 Issue: 08 Pages: 1-19
- DOI
  10.1088/1475-7516/2022/08/025
- Peer Reviewed / Open Access / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702, KAKENHI-PLANNED-20H05859
[Journal Article] New constraints on axion-gauge field dynamics during inflation from Planck and BICEP/Keck data sets2022
- Author(s)
  Paolo Campeti, Ogan Ozsoy, Ippei Obata, Maresuke Shiraishi
- Journal Title
  
  JCAP
  
  Volume: 07 Issue: 07 Pages: 1-32
- DOI
  10.1088/1475-7516/2022/07/039
- Peer Reviewed / Open Access / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702, KAKENHI-PLANNED-20H05859, KAKENHI-PROJECT-19K14718
[Journal Article] Mixed non-gaussianity from axion-gauge field dynamics2019
- Author(s)
  Fujita Tomohiro、Namba Ryo、Obata Ippei
- Journal Title
  
  Journal of Cosmology and Astroparticle Physics
  
  Volume: 2019 Issue: 04 Pages: 044-044
- DOI
  10.1088/1475-7516/2019/04/044
- Peer Reviewed / Open Access
- Data Source
  KAKENHI-PROJECT-17J09103, KAKENHI-PROJECT-19K14702
[Journal Article] Axion Dark Matter Search with Interferometric Gravitational Wave Detectors2019
- Author(s)
  Nagano Koji、Fujita Tomohiro、Michimura Yuta、Obata Ippei
- Journal Title
  
  Physical Review Letters
  
  Volume: 123 Issue: 11 Pages: 111301-111301
- DOI
  10.1103/physrevlett.123.111301
- NAID
  120006724631
- Peer Reviewed / Open Access
- Data Source
  KAKENHI-PROJECT-18K18763, KAKENHI-PROJECT-18H01224, KAKENHI-PROJECT-17J01176, KAKENHI-PROJECT-19K14702
[Presentation] Axionic defects in the CMB: birefringence and gravitational waves2025
- Author(s)
  Ippei Obata
- Organizer
  YU Workshop 2025
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702
[Presentation] Cosmic Birefringence2025
- Author(s)
  Ippei Obata
- Organizer
  CMB B-mode - NEXT
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702
[Presentation] Cosmic Birefringence2025
- Author(s)
  Ippei Obata
- Organizer
  BB meeting
- Invited
- Data Source
  KAKENHI-PROJECT-19K14702
[Presentation] Parity Violation Meets Cosmic Birefringence: Implications for Fundamental Physics2025
- Author(s)
  Ippei Obata
- Organizer
  LeCosPA Meets IPMU
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702
[Presentation] Parity-violating scalar trispectrum from a rolling axion during inflation2024
- Author(s)
  Ippei Obata
- Organizer
  Parity Violation from Home
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702
[Presentation] Can gravitational wave detectors meet the Majoron?2024
- Author(s)
  Ippei Obata
- Organizer
  LVK Collaboration meeting
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702
[Presentation] Axionic defects in the CMB: birefringence and gravitational waves2024
- Author(s)
  Ippei Obata
- Organizer
  COSMO 2024
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702
[Presentation] Primordial scalar trispectrum from axion inflation2024
- Author(s)
  Ippei Obata
- Organizer
  3rd Mini-workshop on the Early Universe
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702
[Presentation] Parity-violation in Cosmology - cosmic birefringence and its implications -2024
- Author(s)
  Ippei Obata
- Organizer
  New Physics from Gravitational Waves
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702
[Presentation] Axion search with the observations of photon's birefringence effect2024
- Author(s)
  Ippei Obata
- Organizer
  Berkeley Week
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702
[Presentation] Can gravitational wave detectors meet the Majoron?2024
- Author(s)
  Ippei Obata
- Organizer
  The 4th Asian-European-Institutes Workshop for BSM
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702
[Presentation] Can gravitational wave detectors meet the Majoron?2024
- Author(s)
  Ippei Obata
- Organizer
  JGRG 33
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702
[Presentation] Can we explain cosmic birefringence without a new light field beyond Standard Model?2024
- Author(s)
  Ippei Obata
- Organizer
  "What is dark matter?" - Comprehensive study of the huge discovery space in dark matter
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702
[Presentation] Parity-violating signals from the effective field theory of Standard Model2024
- Author(s)
  Ippei Obata
- Organizer
  Focus Week Program "Parity violation through CMB observations"
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702
[Presentation] Can gravitational wave detectors meet the Majoron?2024
- Author(s)
  Ippei Obata
- Organizer
  The Fundamentals School
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702
[Presentation] Axion dark matter search with the observations of cosmic birefringence2023
- Author(s)
  Ippei Obata
- Organizer
  Dark Matter 2023: From the Smallest to the Largest Scales
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702
[Presentation] Probing axions with the measurements of photon's birefringence2023
- Author(s)
  Ippei Obata
- Organizer
  Kagoshima Workshop on Particles, Fields and Strings 2023
- Invited
- Data Source
  KAKENHI-PROJECT-19K14702
[Presentation] Parity-odd trispectrum from axion inflation2023
- Author(s)
  Ippei Obata
- Organizer
  Domestic Molecule-type Workshop " Non-linear Nature of Cosmological Perturbations and its Observational Consequences"
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702
[Presentation] Implications of the cosmic birefringence measurement for the axion dark matter search2022
- Author(s)
  Ippei Obata
- Organizer
  17th Patras Workshop on Axions, WIMPs, and WISPs
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702
[Presentation] Probing axions with the measurements of photon's birefringence2022
- Author(s)
  Ippei Obata
- Organizer
  The 7th IBS-ICTP-MultiDark Workshop
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702
[Presentation] Axion Dark Matter Search with Interferometric Gravitational Wave Detectors2019
- Author(s)
  Ippei Obata
- Organizer
  Axion Cosmology
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702
[Presentation] Axion Dark Matter Search with Interferometric Gravitational Wave Detectors2019
- Author(s)
  Ippei Obata
- Organizer
  TAUP 2019
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702
[Presentation] Axion Dark Matter Search with Interferometric Gravitational Wave Detectors2019
- Author(s)
  Ippei Obata
- Organizer
  Axion Wimp 2019
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K14702

1. 道村唯太

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# of Collaborated Products: 1 results
2. 並河俊弥

# of Collaborated Projects: 0 results

# of Collaborated Products: 1 results

Obata Ippei 小幡 一平

小幡 一平 オバタ イッペイ

Research Projects

Research Products

Co-Researchers

Cosmological Research in Axion Physics: Phenomenology of Parity-Violation in Polarized PhotonPrincipal Investigator

Principal Investigator

Project Period (FY)

Research Category

Review Section

Research Institution

[Journal Article] Axionic defects in the CMB: birefringence and gravitational waves2024

Author(s)

Journal Title

Data Source

[Journal Article] Can we explain cosmic birefringence without a new light field beyond Standard Model?2024

Author(s)

Journal Title

DOI

Data Source

[Journal Article] Constraining ultralight ALP dark matter in light of cosmic birefringence2024

Author(s)

Journal Title

DOI

Data Source

[Journal Article] Parity-violating scalar trispectrum from a rolling axion during inflation2024

Author(s)

Journal Title

Data Source

[Journal Article] Axion-gauge dynamics during inflation as the origin of pulsar timing array signals and primordial black holes2024

Author(s)

Journal Title

DOI

Data Source

[Journal Article] Cosmic birefringence tomography with polarized Sunyaev-Zel'dovich effect2023

Author(s)

Journal Title

DOI

Data Source

[Journal Article] Stochastic effects on observation of ultralight bosonic dark matter2023

Author(s)

Journal Title

DOI

Data Source

[Journal Article] First results of axion dark matter search with DANCE2023

Author(s)

Journal Title

DOI

Data Source

[Journal Article] Cosmic birefringence from monodromic axion dark energy2022

Author(s)

Journal Title

DOI

Data Source

[Journal Article] New constraints on axion-gauge field dynamics during inflation from Planck and BICEP/Keck data sets2022

Author(s)

Journal Title

DOI

Data Source

[Journal Article] Mixed non-gaussianity from axion-gauge field dynamics2019

Author(s)

Journal Title

DOI

Data Source

[Journal Article] Axion Dark Matter Search with Interferometric Gravitational Wave Detectors2019

Author(s)

Journal Title

DOI

NAID

Data Source

[Presentation] Axionic defects in the CMB: birefringence and gravitational waves2025

Author(s)

Organizer

Data Source

[Presentation] Cosmic Birefringence2025

Author(s)

Organizer

Data Source

[Presentation] Cosmic Birefringence2025

Author(s)

Obata Ippei 小幡一平

小幡一平オバタイッペイ