Details of a Researcher - Higaki, Tetsutaro

Finite modular axion and radiative moduli stabilization

Tetsutaro Higaki, Junichiro Kawamura, Tatsuo Kobayashi

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 $\tau \sim i\infty$.
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)
Moduli inflation from modular flavor symmetries

Yoshihiko Abe, Tetsutaro Higaki, Fumiya Kaneko, Tatsuo Kobayashi, Hajime Otsuka

Journal of High Energy Physics （Springer Science+Business Media) 6 （ 187 ） 1 - 39 2023.06

Research paper (scientific journal), Joint Work, Accepted

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We study slow-roll inflation model controlled by the modular flavor symmetry.
In the model, the modulus field plays a role of inflaton and the introduction
of the stabilizer field coupled to a modular form in the superpotential
produces the inflaton potential. In order to generate the flat direction for
the slow-roll inflation, we consider the K\"{a}hler potential corrected by the
modular form. It is noted that the modulus field perpendicular to the inflaton
direction is stabilized during the inflation. The model is turns out to be
consistent with the current observations and behaves similarly to the
$\alpha$-attractor models in some parameter spaces. The inflaton rolls down to
the CP-symmetric vacuum at the end of inflation.
- Access to Document (DOI)
Quark masses and CKM hierarchies from S4′ modular flavor symmetry

Yoshihiko Abe, Tetsutaro Higaki, Junichiro Kawamurab, Tatsuo Kobayashi

e-Print: 2301.07439 [hep-ph] （European Physical Journal C) 83 （ 12 ） 2023.01

Research paper (other academic), Joint Work, ISSN 14346044

　View Summary

We propose models to explain the hierarchies of the quark masses and mixing by utilizing the S4′ modular flavor symmetry. The hierarchy is realized by the modulus τ stabilized at Imτ≫1 , where the residual Z4T symmetry is approximately unbroken and the Froggatt–Nielsen mechanism works. It is found that the quark hierarchies are realized only in a few cases of quark representations. We study two models with assigning the modular weights, so that the observed quark hierarchies are explained in the cases of both small and large ratios of the top to bottom Yukawa couplings. We also argue that O(0.1) hierarchies of the O(1) coefficients and the spontaneous CP violation can be realized by imposing another S3 modular symmetry.
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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