arXiv subjects

Yukihiro Kanda

Publications and source records attributed to Yukihiro Kanda.

5 recordsLinked to original sources

arXiv2026

Nambu-Goldstone emissions from the cosmological evolution of global monopoles

We show the emission of the Nambu-Goldstone (NG) bosons from the cosmological evolution of global monopoles. The NG bosons are non-thermally produced from the dynamics of global monopoles such as the pair annihilation of monopole and anti-monopole. Our numerical lattice simulations demonstrate that the spectrum of NG bosons emitted from the scaling evolution of global monopoles has a peak around the horizon scale, as in the case with the global string and the semilocal string. We also estimate the abundance of the pseudo-Nambu-Goldstone (pNG) dark matter when one (or both) of the NG modes has a soft mass.

hep-ph↗

arXiv2026

Emission of Nambu-Goldstone bosons from the semilocal string network

Semilocal cosmic string is a line-like non-topological soliton associated with the breakdown of the $SU(2)_{\rm global} \times U(1)_{\rm gauge}$ symmetry to the $U(1)_{\rm global}$ symmetry. The broken phase has two massless Nambu-Goldstone (NG) modes as dynamical fields, and they can be emitted by semilocal strings. In this paper, we numerically show that such NG bosons are copiously produced with the evolution of the semilocal string network in the early universe. Our numerical analysis shows that the spectrum of produced particles has a peak at low momenta corresponding to the horizon scale. If the emitted NG bosons acquire mass due to soft-breaking terms, they can take the role of dark matter. This scenario typically predicts very light pseudo NG boson dark matter.

hep-ph↗

arXiv2024

Distance-dependent interaction between cosmic strings inspired by higher-dimensional gauge theory

We discuss Abrikosov-Nielsen-Olesen (ANO) strings with the one-loop effective potentials induced by higher-dimensional gauge theory. As our starting point, we consider a five-dimensional $SU(2)$ gauge theory with an extra-dimensional space $S^1/Z_2$. We numerically show the properties of the strings in our model. Especially, we investigate the interaction force between two parallel strings. We find that the interaction force switches from attraction to repulsion as two strings approach each other at a certain parameter region. This interaction is not observed for the ANO strings with the Mexican hat potential. Furthermore, we find that each different factor determines the interaction between large and small interstring distances. We interpret this difference as the origin of the distance-dependent interaction. Our interpretation can also be applied to other scalar potentials. The results in our study give us a new perspective to understand the interaction between the ANO strings with various scalar potentials.

hep-ph↗

arXiv2023

Stability of the embedded string in the $SU(N)\times U(1)$ Higgs model and its application

Since it has been pointed out that physics beyond the Standard Model may be constrained by gravitational waves from cosmic strings, it has been more important to clarify in what cases cosmic strings are formed. We study the stability of the embedded string which is formed when $SU(N)\times U(1)_X$ gauge symmetries are broken to $SU(N-1)\times U(1)_Q$, and find that the stability condition can be determined by two mass ratios of the Higgs and massive gauge bosons, and does not explicitly depend on $N$. We also show that the result can be extended in supersymmetric models. In addition, we apply these results to several models and discuss the important feature of the Higgs to produce the embedded string. Although we find it difficult to be satisfied in normal realistic GUT models, it is possible if $SU(N)$ and $U(1)_X$ have different origins.

hep-ph↗

arXiv2022

Stability of non-topological string in supersymmetric $SU(2)\times U(1)$ gauge theory

We construct a non-topological string solution for a supersymmetric gauge theory with $SU(2)\times U(1)$ gauge symmetry which is spontaneously broken to $U(1)$ by developing the vacuum expectation value of two doublet Higgses. It is a supersymmetric extension of the electroweak string while supersymmetry is unbroken. We discuss the classical stability of the non-topological string by perturbations. We show that the classical stability are determined only by two parameters, and that the allowed region becomes essentially the same as in the electroweak string.

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