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Contents of Works page
Publications
F. Sano, J. Tokuda. "False and genuine decoherence in the early universe: a local observer and time-averaged observables". ArXiv: 2504.10472. Journal Reference: J. High Energ. Phys. 2025, 266 (2025).
The reduced density matrix of primordial curvature perturbations is suffered from IR and UV divergences. We addressed the problem by defining proper observables for a local observer. IR divergence of massless particles are often treated by absorbing the soft modes to background, which does not change the theory since the IR modes is included within the scope of the IR effective theory. Furthermore, it is discussed in literature that equal time correlators exhibit UV divergences even in renormalized theories. The possibly unrenormalizable UV divergence corresponds to rapid oscillatory modes in Wightman function. In this paper, we consider observable quantities in geodesic coordinate with finite time resolution, which absorb the IR modes at the origin to background metric, as well as smearing out oscillating UV contributions.
T. Noumi, F. Sano, Y. Suzuki. "Holographic entanglement entropy in the FLRW universe". ArXiv: 2504.10457. Journal Reference: J. High Energ. Phys. 2025, 115 (2025).
Following the idea of black hole event horizons and the so-called static patch holography, we calculated the holographic entanglement entropy for the subsystem on the cosmological horizons of FLRW universe. We found that, when the matter fields are standard in the sense of the null energy condition, the boundary on/inside the apparent horizon results in the entropy compatible with strong subadditivity. This work would be the first step to constrain the dynamics of the universe from holographic perspective.
S. Aoki, L. Pinol, F. Sano, M. Yamaguchi, Y. Zhu. "Cosmological Correlators with Double Massive Exchanges: Bootstrap Equation and Phenomenology". ArXiv: 2404.09547. Journal Reference: J. High Energ. Phys. 2024, 176 (2024).
This work revealed that the leading-order signal in Cosmological Collider physics may not be the simplest Feynman diagram with additional fields, which involves a single internal propagator of isocurvature modes. We derived the exact formulae for the three-point tree diagram with two internal propagators using the so-called bootstrap method, and explicitly showed that this contribution is naturally larger than those from the single exchange diagrams. Furthermore, we proposed some points of view to distinguish the signals from the single exchange and the double exchange, constraining the interactions between inflaton and isocurvature modes.
S. Aoki, T. Noumi, F. Sano, M. Yamaguchi. "Analytic Formulae for Inflationary Correlators with Dynamical Mass". ArXiv: 2312.09642. Journal Reference: J. High Energ. Phys. 2024, 73 (2024).
In this work, we derived the analytic expression for the scale dependence of the Cosmological Collider signal dominantly induced by non-shift symmetric coupling ignored in previous works due to its slow-roll suppressed coupling constant. In particular, we revealed that the scale dependence from inflaton's background evolution naturally produces an observably large correction to perturbation's scale invariant correlations.
Academic Talks
Invited talks
Jun. 15–Jun. 21, 2025. Invited talk at "2025 APCTP-IBS Focused Research Program: The origin and evolution of the Universe", Asia Pacific Center for Theoretical Physics, Pohang, Korea. "Cosmological Collider as an Interaction Probe: Scale-Dependence and Diagrams".
Seminar talks
Sep. 8, 2025. Seminar talk at Leung Center for Cosmology and Particle Astrophysics, Taipei, Taiwan. "Decoherence of Primordial Perturbations in the View of a Local Observer".
Aug. 27, 2025. Seminar talk at National Tsing Hua University, Hsinchu, Taiwan. "Holographic Entanglement Entropy in the FLRW Universe".
Jul. 7, 2025. Seminar talk at Perimeter Institute for Theoretical Physics, Waterloo, Canada. "Decoherence of Primordial Perturbations in the View of a Local Observer".
Jun. 4, 2025. Seminar talk at Yonsei University, Seoul, Korea. "Decoherence of Primordial Perturbations in the View of a Local Observer".
May 8, 2025. Seminar talk at Kyushu University, Fukuoka, Japan. "Decoherence of Primordial Perturbations in the View of a Local Observer".
May 7, 2025. Seminar talk at Saga University, Saga, Japan. "Decoherence of Primordial Perturbations in the View of a Local Observer".
Apr. 25, 2025. Seminar talk at Waseda University, Tokyo, Japan. "Decoherence of Primordial Perturbations in the View of a Local Observer".
Apr. 22, 2025. Seminar talk at RIKEN, Wako, Japan. "Decoherence of Primordial Perturbations in the View of a Local Observer".
Apr. 3, 2025. Seminar talk at Scuola Internazionale Superiore di Studi Avanzati, Trieste, Italy. "On IR/UV divergence of inflationary decoherence".
Jan. 27, 2025. Seminar talk at Ecole Normale Supérieure, Paris, France. "UV and IR Regularization for Decoherence of Primordial Perturbations".
Dec. 11, 2024. Seminar talk at Academia Sinica, Taipei, Taiwan. "Cosmological Collider as an Interaction Probe: Scale-Dependence and Diagrams".
Jul. 10, 2024. Seminar talk at Instituto de Física Teórica, Madrid, Spain. "Cosmological Collider as an Interaction Probe: Scale-Dependence and Diagrams".
Jun. 17, 2024. Seminar talk at Chulalongkorn University, Bangkok, Thailand. "Cosmological Collider as an Interaction Probe: Scale-Dependence and Diagrams".
Dec. 6, 2023. Seminar talk at Tohoku University, Sendai, Japan. "Analytic Formulae for Inflationary Correlators with Dynamical Mass".
Nov. 23, 2023. Seminar talk at Tsinghua University, Beijing, China. "Analytic Formulae for Inflationary Correlators with Dynamical Mass".
Nov. 7, 2023. Seminar talk at Hong Kong University of Science and Technology, Hong Kong. "Analytic Formulae for Inflationary Correlators with Dynamical Mass".
Oct. 18, 2023. Seminar talk at Ecole Normale Supérieure, Paris, France. "Analytic Formulae for Inflationary Correlators with Dynamical Mass".
Contributed / Poster
Aug. 17–Aug. 22, 2025. Contributed talk at "29th International Summer Institute on Phenomenology of Elementary Particle Physics and Cosmology (SI 2025)", Utop Marina Hotel & Resort, Yeosu, Korea. "Decoherence of primordial perturbations in the view of a local observer".
Jun. 23–Jun. 27, 2025. Poster presentation at "Quantum Information in Quantum Gravity 2025", Perimeter Institute for Theoretical Physics, Waterloo, Canada. "Holographic Entanglement Entropy in the FLRW Universe".
Jun. 16–Jun. 20, 2025. Contributed talk at "Amplitudes 2025", Seoul National University, Seoul, Korea. "Cosmological Correlators with Double Massive Exchanges".
Feb. 17–Feb. 21, 2025. Poster presentation at "Quantum Gravity and Information in Expanding Universe", Yukawa Institute for Theoretical Physics, Kyoto, Japan. "UV and IR Regularization for Decoherence of Primordial Perturbations".
Jan. 22–Jan. 24, 2025. Contributed talk at "Avenues of Quantum Field Theory in Curved Spacetime 2025", Institut Denis Poisson, Tours, France. "Decoherence of Primordial Perturbations and Maldacena's Consistency Conditions".
Jan. 12–Jan. 18, 2025. Contributed talk at "KIAS-IBS-CKC Joint Workshop on Particle, String and Cosmology", High1 resort, JeongSun, Korea. "Decoherence of Primordial Perturbations and Maldacena's Consistency Conditions".
Dec. 2–Dec. 6, 2024. Contributed talk at "Cosmological Correlators in Taiwan", Leung Center for Cosmology and Particle Astrophysics, Taipei, Taiwan. "Analytic Formulae for Inflationary Correlators with Dynamical Mass".
Oct. 21–Oct. 25, 2024. Poster presentation at "27th International Conference on Particle Physics and Cosmology (COSMO 2024)", Kyoto University, Kyoto, Japan. "Decoherence of Primordial Perturbations in Views of Geodesic Observers".
Sep. 3–Sep. 6, 2024. Contributed talk at "Fourth Mini-workshop on the Early Universe", Yatsugatake Commons, Hokuto, Japan. "Decoherence of Primordial Perturbations in Views of Geodesic Observers".
Aug. 3–Aug. 7, 2024. Contributed talk at "28th International Summer Institute on Phenomenology of Elementary Particles and Cosmology (SI 2024)", Linyi University, Linyi, China. "Decoherence of Primordial Perturbations in Views of Geodesic Observers".
Aug. 1–Aug. 2, 2024. Contributed talk at "Amplitudes Methods for Gravity and Cosmology II", Korea Institute for Advanced Study, Seoul, Korea. "Analytic Formulae for Inflationary Correlators with Dynamical Mass".
Jul. 22–Jul. 26, 2024. Contributed talk at "IBS CTPU-CGA 2024 Summer School and Workshop for Particle Physics and Cosmology in Korea", Muju Deogyusan Resort, Muju, Korea. "Decoherence of Primordial Perturbations in Views of Geodesic Observers".
Jul. 15–Jul. 19, 2024. Contributed talk at "Quantum Gravity Phenomenology in the Multi-messenger Era (QGMM 24)", Complutense University of Madrid, Madrid, Spain. "Analytic Formulae for Inflationary Correlators with Dynamical Mass".
Jun. 10–Jun. 14, 2024. Contributed talk at "CosmoGravitas: An International Conference on Cosmology and Gravity", Mahidol University, Nakhon Sawan, Thailand. "Analytic Formulae for Inflationary Correlators with Dynamical Mass".
Mar. 24–Mar. 29, 2024. Poster presentation at "The Future of High Energy Physics: A New Generation, A New Vision", Aspen Center for Physics, Aspen, the US. "Analytic Formulae for Inflationary Correlators with Dynamical Mass".
Feb. 19–Feb. 23, 2024. Contributed talk at "The 2nd Young Researchers' Workshop of the Extreme Universe Collaboration", Shirahamaso, Takashima, Japan. "Analytic Formulae for Inflationary Correlators with Dynamical Mass".
Jan. 29–Jan. 1, 2024. Contributed talk at "YITP long-term workshop: Gravity and Cosmology 2024 (GC 2024)", Yukawa Institute for Theoretical Physics, Kyoto, Japan. "Analytic Formulae for Inflationary Correlators with Dynamical Mass".
Jan. 21–Jan. 27, 2024. Contributed talk at "High1 Workshop on Particle, String and Cosmology", High1 Resort, JeongSun, Korea. "Analytic Formulae for Inflationary Correlators with Dynamical Mass".
Nov. 27–Dec. 1, 2023. Contributed talk at "The 32nd Workshop on General Relativity and Gravitation in Japan (JGRG 32)", Nagoya University, Nagoya, Japan. "Analytic Formulae for Inflationary Correlators with Dynamical Mass".
Nov. 18–Nov. 20, 2023. Contributed talk at "International Conference on Modified Gravity (MOGRA 2023)", Central China Normal University, Wuhan, China. "Analytic Formulae for Inflationary Correlators with Dynamical Mass".
Nov. 10–Nov. 13, 2023. Contributed talk at "International Symposium on Cosmology and Particle Astrophysics (CosPA 2023)", The Chinese University of Hong Kong, Hong Kong. "Analytic Formulae for Inflationary Correlators with Dynamical Mass".
Sep. 11–Sep. 15, 2023. Contributed talk at "26th International Conference on Particle Physics and Cosmology (COSMO 2023)", Instituto de Física Teórica, Madrid, Spain. "Scale Dependent Cosmological Collider Signals from Dynamical Mass".
Jul. 24–Jul. 28, 2023. Contributed talk at "IBS CTPU-CGA 2023 Summer Workshop and School on Particle Physics in Korea", Muju Deogyusan Resort, Muju, Korea. "Scale Dependent Cosmological Collider Signals from Dynamical Mass".
Jul. 18–Jul. 20, 2023. Contributed talk at "Gravity 2023: Dawn of Field theoretic approach", Yukawa Institute for Theoretical Physics, Kyoto, Japan. "Scale Dependent Cosmological Collider Signals from Dynamical Mass".
Nonpublic workshops
Jul. 28–Aug. 1, 2025. Talk at "IBS CTPU-CGA 2025 Summer School and Workshop for High Energy Physics and Cosmology in Korea", Best Western Hotel, Jeonju, Korea. "Holographic Entanglement Entropy in the FLRW Universe".
Apr. 7–Apr. 12, 2025. Talk at "Prague Spring 2025: CAS - IBS CTPU-CGA - ISCT Workshop in Cosmology, Gravitation and Particle Physics", Institute of Physics of the Czech Academy of Sciences, Prague, Czech. "On IR/UV divergence of inflationary decoherence".
Sep. 8–Sep. 12, 2024. Talk at "IBS CTPU-CGA, Tokyo Tech, USTC 2024 summer school and workshop on cosmology, gravity, and particle physics", Kyukamura Tateyama, Tateyama, Japan. "Decoherence of Primordial Perturbations in Views of Geodesic Observers".
Jun. 3–Jun. 7, 2024. Talk at "IBS CTPU-CGA 2024 Workshop on Cosmological Collider", Institute for Basic Science, Daejeon, Korea. "Cosmological Collider as an Interaction Probe: Scale-Dependence and Diagrams".
Oct. 9–Oct. 14, 2023. Talk at "CAS-JSPS-IBS CTPU-CGA Workshop in Cosmology, Gravitation and Particle Physics", Institute of Physics of the Czech Academy of Sciences, Prague, Czech. "Analytic Formulae for Inflationary Correlators with Dynamical Mass".
Aug. 28–Sep. 1, 2023. Talk at "CAS-JSPS-IBS CTPU-CGA 2023 Summer Workshop on Cosmology, Gravity, Particle Physics", Kyukamura Lake Shikotsu, Chitose, Japan. "Scale Dependent Cosmological Collider Signals from Dynamical Mass".
May 17– May 20, 2023. Talk at "Korea-Japan joint workshop on Particle Physics, Cosmology, and Gravity", Jeonbuk National University, Jeonju, Korea. "Non-Gaussianities from heavy particles with time dependent mass".
Presentation files (Only those based on published works)
"Decoherence of Primordial Perturbations in the View of a Local Observer". Based on 2504.10472. Used in a seminar talk at Leung Center for Cosmology and Particle Astrophysics, Taipei, Taiwan, Sep. 8, 2025.
"Holographic entanglement entropy in the FLRW universe". Based on 2504.10457. Used in a seminar talk at National Tsing Hua University, Hsinchu, Taiwan, Aug. 29, 2025.
"Cosmological Collider as an Interaction Probe: Scale-Dependence and Diagrams". Based on 2312.09642 and 2404.09547. Used in an invited talk at "2025 APCTP-IBS Focused Research Program: The origin and evolution of the Universe", Asia Pacific Center for Theoretical Physics, Pohang, Korea, Jun. 18, 2025.
Grants
Apr. 25, 2023–Mar. 31, 2026. Grant-in-Aid for JSPS Fellows. KAKENHI Project Number 23KJ0938. "初期宇宙の密度揺らぎを用いた標準模型を超える物理の検出に関する包括的理論研究".
Teaching
Teaching Assistant
Spring semester (2nd quarter), 2022. "Analytical Mechanics (Exercise)" at the undergraduate level. Tokyo Institute of Technology.
Autumn semester, 2021. "Exercises in Physics II, Electromagnetics" at the undergraduate level. Tokyo Institute of Technology.
Spring semester, 2021. "Exercises in Physics I, Classical Mechanics" at the undergraduate level. Tokyo Institute of Technology.
Autumn semester, 2020. "Exercises in Physics II, Electromagnetics" at the undergraduate level. Tokyo Institute of Technology.
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