arXiv subjects

Tsubasa Sugeno

Publications and source records attributed to Tsubasa Sugeno.

3 recordsLinked to original sources

arXiv2026

Anomalies in family unification models from bordism classification

We study anomalies in family unification models within the framework of the bordism classification of invertible field theories. These models are based on four-dimensional $\mathcal{N}=1$ supersymmetric nonlinear sigma models, in which the three generations of quarks and leptons arise as superpartners of the sigma model fields. We focus on models whose target spaces are constructed from the exceptional group $E_{7}$ and its subgroups. For the consistency of the theory, sigma model anomalies must be cancelled. We show the absence of global sigma model anomalies, which are encoded in the torsion part of the relevant bordism groups, by explicitly computing these groups using the Atiyah-Hirzebruch spectral sequence. In constructing family unification models, symmetries acting on the coset spaces are gauged, which may introduce additional anomalies. We identify the relevant bordism groups in this setting and demonstrate that no global anomalies arise when the isotropy subgroup of the coset space is gauged.

hep-th↗

arXiv2025

Axion Cosmology with Multi-Branch Yang-Mills

It is known that Yang-Mills theories, especially in the large-$N$ limit, exhibit a $θ$-vacuum structure with a multi-branched vacuum energy. In this work, we demonstrate that this multi-branch structure can play a crucial role in axion cosmology when the axion acquires its mass from the Yang-Mills sector, even when that sector is never reheated by the inflaton. The key observation is that the axion potential is directly tied to the tunneling rate between adjacent branches. We find qualitatively new phenomena, including a new class of first-order phase transitions, bouncing bubbles, and nested "bubbles-within-bubbles." When the axion has a decay constant around the Planck scale, as motivated by the string Axiverse, the axion can be driven near the hilltop by inflationary dynamics, allowing the phase transition to be triggered. The associated energy release can be large enough to generate a significant stochastic gravitational-wave background, produce primordial black holes, or populate the Yang-Mills sector with particles. These phenomena represent novel predictions of the Axiverse and should be taken into account when assessing the cosmological impact of axions or axion-like particles. To recover conventional axion cosmology, one must suppress or avoid the dynamics discussed in this work.

hep-ph↗

arXiv2025

Large $θ$ angle in two-dimensional large $N$ $\mathbb{CP}^{N-1}$ model

In confining large $N$ theories with a $θ$ angle such as four-dimensional $\mathrm{SU}(N)$ pure Yang-Mills theory, there are multiple metastable vacua and it makes sense to consider the parameter region of ``large $θ$ of order $N$'' despite the fact that $θ$ is a $2π$-periodic parameter. We investigate this parameter region in the two-dimensional $\mathbb{CP}^{N-1}$ model by computing the partition function on $T^2$. When $θ/N$ is of order $ \mathcal{O}(0.1) $ or less, we get perfectly sensible results for the vacuum energies and decay rates of metastable vacua. However, when $θ/N$ is of order $\mathcal{O}(1) $, we encounter a problem about saddle points that would give larger contributions to the partition function than the true vacuum. We discuss why it might not be straightforward to resolve this problem.

hep-th↗