Axial U(1) current in Grabowska and Kaplan's formulation

Recently, Grabowska and Kaplan suggested a non-perturbative formulation of a chiral gauge theory, which consists of the conventional domain-wall fermion and a gauge field that evolves by the gradient flow from one domain wall to the other. In this paper, we discuss the U(1) axial-vector current in 4 dimensions using this formulation. We introduce two sets of domain-wall fermions belonging to complex conjugate representations so that the effective theory is a 4-dimensional vector-like gauge theory. Then, as a natural definition of the axial-vector current, we consider a current that generates the simultaneous phase transformations for the massless modes in 4 dimensions. However, this current is exactly conserved and does not reproduce the correct anomaly. In order to investigate this point precisely, we consider the mechanism of the conservation. We find that this current includes not only the axial current on the domain wall but also a contribution from the bulk, which is non-local in the sense of 4-dimensional fields. Therefore, the local current is obtained by subtracting the bulk contribution from it.Comment: 25 pages, 1 figur

Scalegenesis and fermionic dark matters in the flatland scenario

We propose an extension of the standard model with Majorana-type fermionic dark matters based on the flatland scenario where all scalar coupling constants, including scalar mass terms, vanish at the Planck scale, i.e. the scalar potential is flat above the Planck scale. This scenario could be compatible with the asymptotic safety paradigm for quantum gravity. We search the parameter space so that the model reproduces the observed values such as the Higgs mass, the electroweak vacuum and the relic abundance of dark matter. We also investigate the spin-independent elastic cross section for the Majorana fermions and a nucleon. It is shown that the Majorana fermions as dark matter candidates could be tested by dark matter direct detection experiments such as XENON, LUX and PandaX-II. We demonstrate that within the minimal setup compatible with the flatland scenario at the Planck scale or asymptotically safe quantum gravity, the extended model could have a strong predictability.Comment: 23 pages, 9 figures, Version published in EPJ

標準模型及びそれを超えたヒッグス物理における非摂動的側面

京都大学新制・課程博士博士(理学)甲第23000号理博第4677号新制||理||1671(附属図書館)京都大学大学院理学研究科物理学・宇宙物理学専攻(主査)教授 川合 光, 教授 田中 貴浩, 准教授 吉岡 興一学位規則第4条第1項該当Doctor of ScienceKyoto UniversityDFA

Electroweak axion string and superconductivity

We study the axion strings with the electroweak gauge flux in the DFSZ axion model and show that these strings, called the electroweak axion strings, can exhibit superconductivity without fermionic zero modes. We construct three types of electroweak axion string solutions. Among them, the string with $W$-flux can be lightest in some parameter space, which leads to a stable superconducting cosmic string. We also show that a large electric current can flow along the string due to the Peccei-Quinn scale much higher than the electroweak scale. This large current induces a net attractive force between the axion strings with the same topological charge, which opens a novel possibility that the axion strings form Y-junctions in the early universe.Comment: 35 pages, 8 figures; v3: published versio