Details of a Researcher - Higaki, Tetsutaro

Spontaneous CP violation and partially broken modular flavor symmetries

Tetsutaro Higaki, Tatsuo Kobayashi, Kaito Nasu, Hajime Otsuka

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.
Moduli stabilization in finite modular symmetric models

Yoshihiko Abe, Komei Goto, Testutaro Higaki, Tatsuo Kobayashi, Kaito Nasu

2024.05

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We study vacua of moduli potential consisting of multiple contribution 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 de Sitter vacuum is realized with a multiple modular form case and obtain a non-trivial vacuum which is 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 by a numerical and analytically. It is also found that vacua obtained in this paper preserve CP symmetry.
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 $\tau \sim i\infty$.
- Access to Document (DOI)
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.
- Access to Document (DOI)
Quark and lepton hierarchies from S4' modular flavor symmetry

Yoshihiko Abe, Tetsutaro Higaki, Junichiro Kawamura, Tatsuo Kobayashi

Physics Letters B （Elsevier) 842 （ 137977 ） 1 - 9 2023.07

Research paper (scientific journal), Accepted

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We propose models in which the hierarchical structures of the masses and
mixing in both quark and lepton sectors are explained by the $S_4^\prime$
modular flavor symmetry near the fixed point $\tau \sim i\infty$. The model
provides the first explicit example which explains hierarchies of both quarks
and leptons. The hierarchies are realized by powers of $\epsilon = e^{2\pi i
\tau/4} = \mathcal{O}(0.01)$ and $2\,\mathrm{Im}\,\tau \sim 5$, where $\tau$
being the modulus. The small parameter $\epsilon$ plays a role of flavon in the
Froggatt-Nielsen mechanism under the residual $Z_4^T$ symmetry, and powers of
$2\,\mathrm{Im}\,\tau$ in the Yukawa couplings are controlled by modular
weights via the canonical normalization. The doublet quarks are identified to a
$S_4^\prime$ triplet to explain the hierarchical structure of the quark mixing
angles, while the doublet leptons are composed of three singlets for the large
mixing angles in the lepton sector. We show that the $S_4^\prime$ modular
symmetry alone can explain the hierarchies in both quark and lepton sectors by
$\mathcal{O}(1)$ coefficients.
- Access to Document (DOI)

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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