Details of a Researcher - Higaki, Tetsutaro

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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Spontaneous CP violation and partially broken modular flavor symmetries

Tetsutaro Higaki, Tatsuo Kobayashi, Kaito Nasu, Hajime Otsuka

Journal of High Energy Physics 2024 ( 9 ) 2024.05

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We study the realization of spontaneous CP violation through moduli
stabilization. In modular flavor models, the source of CP violation is the
vacuum expectation values of the complex structure moduli of toroidal compact
space. We demonstrate that the combined effects of Type IIB flux
compactifications with modular invariant couplings between the moduli and
matter fields can induce spontaneous CP violation without or with supersymmetry
breaking. Furthermore, some general properties of CP and modular invariant
scalar potentials are presented. It is found that certain modifications or
partial breakings of modular symmetry are useful in generating spontaneous CP
violation.
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Finite modular axion and radiative moduli stabilization

Tetsutaro Higaki, Junichiro Kawamura, Tatsuo Kobayashi

Journal of High Energy Physics (Journal of High Energy Physics) 2024 ( 4 ) 2024.02

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We propose a simple setup which can stabilize a modulus field of the finite
modular symmetry by the Coleman-Weinberg potential. Our scenario leads to a
large hierarchy suppressing instanton-like corrections $e^{2\pi i\tau}$ and to
a light axion identified as $\mathrm{Re} \tau$, where $\tau$ is the modulus
field. This stabilization mechanism provides the axion solution to the strong
CP problem. The potential has a minimum at a large $\mathrm{Im}\tau$ which
suppresses explicit $U(1)_{\mathrm{PQ}}$ violation terms proportional to
$e^{-2\pi {\mathrm{Im}\tau}}$, and hence the quality of the axion is ensured by
the residual symmetry associated with the $T$-transformation, $\tau \to \tau
+1$, around the fixed point $\tau \sim i\infty$.
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Fermion Hierarchies in SU(5) Grand Unification from Γ6' Modular Flavor Symmetry

Yoshihiko Abe, Tetsutaro Higaki, Junichiro Kawamura, Tatsuo Kobayashi

Journal of High Energy Physics (Springer Science+Business Media) 08 ( 097 ) 1 - 25 2023.08

Research paper (scientific journal), Accepted

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We construct a model in which the hierarchies of the quark and lepton masses and mixing are explained by the Γ′6 modular flavor symmetry. The hierarchies are realized by the Froggatt-Nielsen-like mechanism due to the residual ZT6 symmetry, approximately unbroken at τ∼i∞. We argue that the Γ(′)6 symmetry is the minimal possibility to realize the up-type quark mass hierarchies, since the Yukawa matrix is symmetric. We find a combination of the representations and modular weights and then show numerical values of O(1) coefficients for the realistic fermion hierarchies.
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Presentations 【 Display / hide 】

Finite modular axion

檜垣徹太郎

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

Particle physics and cosmology from string compactification,

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

Tetsutaro Higaki

Kobe Workshop on Cosmology and Fundamental Physics 2023,

2023.03
,
Oral presentation (invited, special)
New 4D EFT from 10D non-Abelian DBI action in magnetic compactifications

Tetsutaro Higaki

KEK Theory Workshop 2021,

2021.12
,
Oral presentation (general)
4D effective action from 10D non-Abelian DBI action with magnetic flux background

Tetsutaro Higaki

Strings and Fields 2021,

2021.08
,
Oral presentation (general)

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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

-

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

-

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

-

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