Details of a Researcher - Higaki, Tetsutaro

Non-Abelian $A_4$ vortices in $SO(3)$ gauge theory and non-invertible symmetries

Yoshihiko Abe, Tetsutaro Higaki, Kazuya Murakami, Muneto Nitta, Ryo Yokokura

2026.07

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We construct finite-tension non-Abelian vortex solutions in a renormalizable $(3+1)$-dimensional $SO(3)$ gauge theory Higgsed to the tetrahedral group $A_4$ by a Higgs field in the spin-3 representation. Since the vacuum manifold is $SO(3)/A_4$, the vortices are characterized by the non-Abelian fundamental group $π_1(SO(3)/A_4)\simeq \widetilde{A}_4$, the binary tetrahedral group. We obtain explicit axisymmetric vortex solutions carrying holonomies corresponding to the order-two and order-three conjugacy classes of $A_4$, determine their tensions numerically, and show that they exhibit type-I, type-II, and Bogomol'nyi--Prasad--Sommerfield-like behavior depending on the Higgs and gauge boson mass ratios. The vortices are classified by conjugacy classes of $\widetilde{A}_4$, while their infrared descriptions are labeled by conjugacy classes of $A_4$. We further demonstrate that the smooth finite-tension vortices reduce in the infrared to Gukov--Witten surface operators of the $A_4$ discrete gauge theory, thereby establishing a finite-energy ultraviolet completion of non-invertible defects in a renormalizable gauge-Higgs theory.
Finite modular Coleman-Weinberg inflation

Yoshihiko Abe, Komei Goto, Tetsutaro Higaki, Junichiro Kawamura, Tatsuo Kobayashi

2026.07

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We propose a modular symmetric inflationary model based on a Coleman--Weinberg potential generated by integrating out heavy vector-like quarks that couple to the complex modulus field $τ$ through modular forms. In this framework, the imaginary part of modulus $τ$ plays the role of the inflaton, while the real part is identified with a heavy axion. We show that the model successfully explains the current cosmological observations. We further discuss reheating through modulus-dependent gauge kinetic functions and the cosmology of the axion. The axion oscillation dominates over the Universe after the reheating via inflaton decay, and then it decays before Big Bang Nucleosynthesis in the viable parameter region. The quantum fluctuation of the axion can be of order $\mathcal{O}(1)\% $ of that of the inflaton, which would induce isocurvature perturbations that may be detectable in future observations.
Black hole thermodynamics and KK photon quantum corrections in 2D effective dilaton gravity

Yoshihiko Abe, Tetsutaro Higaki, Yu Miyauchi

2026.06

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We study black hole thermodynamics using a two-dimensional effective theory obtained by dimensional reduction of four-dimensional Einstein--Maxwell theory. For spherically symmetric charged black holes, the resulting dilaton gravity has a nonlinear potential that reproduces the semiclassical phase structure of four-dimensional AdS black holes, including the Hawking--Page transition and the small/large Reissner--Nordström--AdS black hole transition. This shows that the two-dimensional theory before taking the near-horizon and near-extremal limits captures non-extremal thermodynamics beyond the Jackiw--Teitelboim gravity regime. We also include electromagnetic Kaluza--Klein modes on the internal sphere and integrate them out to derive the one-loop effective dilaton gravity. At leading order in the derivative expansion, these corrections appear as constant shifts in the black hole entropy and in the effective charge parameter of the dilaton potential. Therefore, the semiclassical phase structure is not qualitatively modified within this leading local approximation.
Large and small hierarchies from finite modular symmetries

Higaki T., Kawamura J., Kobayashi T., Nasu K., Sakuma R.

Journal of High Energy Physics 2025 ( 5 ) 2025.05

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We study the moduli stabilization by the radiative corrections due to the moduli dependent vector-like masses invariant under the finite modular symmetry. The radiative stabilization mechanism can stabilize the modulus τ of the finite modular symmetry Γ<inf>N</inf> (N ∈ ℕ) at Im τ ≫ 1, where the shift symmetry τ → τ + 1 remains unbroken approximately. The shift symmetry can be considered as the residual ℤ<inf>N</inf> symmetry which realizes the Froggatt-Nielsen mechanism with the hierarchy parameter e<sup>−2πIm τ/N</sup> ≪ 1. In this work, we study the stabilization of multiple moduli fields, so that various hierarchical values of the modular forms coexist in a model. For example, one modulus stabilized at Im τ<inf>1</inf> ∼ 3 is responsible for the hierarchical structure of the quarks and leptons in the Standard Model, and another modulus stabilized at Im τ<inf>2</inf> ∼ 15 can account for the flatness of the Re τ<inf>2</inf> direction which may be identified as the QCD axion.
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Modulus Stabilization in Finite Modular Symmetric Models

Abe Y., Goto K., Higaki T., Kobayashi T., Nasu K.

Progress of Theoretical and Experimental Physics 2025 ( 2 ) 2025.02

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We study the vacua of modulus potentials consisting of multiple contributions of modular forms in a finite modular symmetry. If the potential is given by a single modular form, the Minkowski vacuum is realized at the fixed point of the modular symmetry. We show that the de Sitter vacuum is realized with a multiple modular form case and obtain a nontrivial vacuum away from the fixed point, i.e. a large modulus vacuum expectation value, depending on the choice of the weight and representation of the modular forms. We study these vacua numerically and analytically. It is also found that the vacua obtained in this paper preserve CP symmetry.
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Presentations 【 Display / hide 】

Moduli from compactifications

檜垣徹太郎

[Domestic presentation] “Particle Physics and Cosmology from String Compactification" 7th meeting,

2026.09
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Oral presentation (invited, special)
Moduli Stabilization and its Applications to Phenomenology

檜垣徹太郎

[Domestic presentation] これまでとこれからの、素粒子と弦の現象論,

2024.09
,
Oral presentation (invited, special)
Finite modular axion

檜垣徹太郎

[Domestic presentation] Particle Physics and Cosmology from String Compactification 2nd meeting,

2024.02
,
Oral presentation (invited, special)
Approaches to effective field theories of string theory

檜垣徹太郎

[Domestic presentation] Particle physics and cosmology from string compactification,

2023.09
,
Oral presentation (invited, special)
Modular flavor symmetry and cosmology

Tetsutaro Higaki

[International presentation] Kobe Workshop on Cosmology and Fundamental Physics 2023,

2023.03
,
Oral presentation (invited, special)

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Research Projects of Competitive Funds, etc. 【 Display / hide 】

沼地予想とモジュライから探る究極理論の観測的性質（基盤研究(C)）

2022.04

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2027.03

基盤研究(C), Principal investigator
隠れたセクターの場や粒子が引き起こす多様な宇宙現象を用いた究極理論探査（基盤研究A・分担）

2015.04

-

2018.03

Coinvestigator(s)
超弦理論におけるモジュライ場の現象論的、宇宙論的側面の研究（若手研究B）

2013.04

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2015.03

Principal investigator
超弦理論におけるモジュライ場の現象論的、宇宙論的側面の研究（日本学術振興会優秀若手研究者海外派遣事業 (特別研究員)）

2009

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2010

Principal investigator
超弦理論におけるモジュライ場の現象論的、宇宙論的側面の研究（学振PD）

2007.04

-

2010.03

Principal investigator