Abstract:

In higher-dimensional gauge theories, although there exists considerable arbitrariness in the selection of boundary conditions, the mechanism for choosing them remains unexplained. Some boundary conditions are connected through gauge transformations, forming equivalence classes. Classifying them is an important step toward resolving the issue of arbitrariness. We have discovered Trace Conservation Laws, powerful necessary conditions, and achieved a complete classification of equivalence classes in 1- and 2-dimensional orbifold models. We will report on our new classification method and its results.

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Abstract:

Recent progresses in the measurements of the electric dipole moment (EDM) of the electron using the paramagnetic atom or molecule are remarkable. In this paper, we calculate a contribution to the electron EDM at three-loop level, introducing the CP-violating Yukawa couplings of new SU(2)L multiplets. At two-loop level, the Yukawa interactions generate a CP-violating dimension-six operator, composed of three SU(2)L field strengths, called the electroweak Weinberg operator. Another one-loop diagram with the operator inserted induces the electron EDM. We find that even if new SU(2)L particles have masses around TeV-scale, the electron EDM may be larger than the Standard Model contribution to the paramagnetic atom or molecule EDMs. We also discuss the relation between the Barr-Zee diagram contribution at two-loop level and the three-loop one, assuming that the SM Higgs has new Yukawa interactions with the SU(2)L multiplets.

Abstract:

We study for the first time the gravitational waves generated during the collapse of domain walls, incorpo- rating the potential bias in the lattice simulations. The final stages of domain wall collapse are crucial for the production of gravitational waves but have remained unexplored due to computational difficulties. As a significant application of this new result, we show that the observed NANOGrav, EPTA, PPTA, and CPTA data, which indicate stochastic gravitational waves in the nanohertz regime, can be attributed to axion do- main walls coupled to QCD. In our model, non-perturbative effects of QCD induce a temperature-dependent bias around the QCD crossover, inducing the rapid collapse of the domain walls. We use sophisticated lattice simulations that account for the temperature-dependent bias to measure the gravitational waves resulting from the domain wall annihilation. We also discuss the future prospects for accelerator-based searches for the axion and the potential for the formation and detection of primordial black holes.

Abstract:

We develop a C++ package of the STOchastic LAttice Simulation (STOLAS) of cosmic inflation. It performs the numerical lattice simulation in the application of the stochastic-δN formalism. STOLAS can directly compute the three-dimensional map of the observable curvature perturbation without estimating its statistical properties. In its application to two toy models of inflation, chaotic inflation and Starobinsky’s linear-potential inflation, we confirm that STOLAS is well-consistent with the standard perturbation theory. Furthermore, by introducing the importance sampling technique, we have success in numerically sampling the current abundance of primordial black holes in a non-perturbative way. 

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Abstract:

In the standard cosmological scenario, the energy of the inflaton after inflation must be transferred to radiation energy—a process known as reheating. It is known that if the coupling of the inflaton is sufficiently strong, resonant particle production occurs through non-perturbative effects referred to as preheating. This leads to an explosive decay of the inflaton into radiation. However, if the inflaton remains at the end of the preheating phase, it may once again dominate the energy density during the inflaton oscillation phase, potentially returning the universe to a matter-dominated era. Investigating the boundary between scenarios where reheating concludes during the preheating phase and those where it does not is an important issue.

In this presentation, we consider reheating after axion inflation as a specific model. In this model, it is known that due to gauge boson instability, explosive production of gauge bosons occurs while the axion undergoes several oscillations. Consequently, it is thought that gauge bosons occupy most of the energy at the end of preheating. We discuss how reheating concludes in this scenario.

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Abstract:

A detection scheme is explored for light dark matter, such as axion dark matter or dark photon dark matter, using a Paul ion trap system. We first demonstrate that a qubit, constructed from the ground and first excited states of vibrational modes of ions in a Paul trap, can serve as an effective sensor for weak electric fields due to its resonant excitation. As a consequence, a Paul ion trap allows us to search for weak electric fields induced by light dark matter with masses around the neV range. Furthermore, we illustrate that an entangled qubit system involving N ions can enhance the excitation rate by a factor of N^2. The sensitivities of the Paul ion trap system to axion-photon coupling and gauge kinetic mixing can reach previously unexplored parameter space.

Abstract:

We reexamined the connection between the Hawking radiation of a Schwarzschild black hole formed from collapse and ultraviolet(UV) physics with the local Lorentz symmetry violation or the existence of a minimal length. Significant modifications are reported after the scrambling time in both cases, which reflects the UV sensitivity of Hawking radiation. Depending on the physics at the singularity, Hawking radiation with the modified dispersion relation may be largely suppressed with a striking tunneling phenomenon behind. The Hawking wavepacket may exceed the size of the black hole under the generalized uncertainty principle that it longer employs the near horizon Unruh vacuum with a diminishing Hawking radiation amplitude. While a turned-off effect is shared in these two implementations, the Hawking temperature remains the same or only perturbatively corrected.

Abstract:

The phenomenon where the properties of the muon do not align with those predicted by the Standard Model of physics, known as the "muon g-2 anomaly," has garnered significant attention. While the Standard Model is a theory that explains elementary particles and their interactions, this discrepancy might be a sign of new physics. To explain this anomaly, a Two Higgs Doublet Model with Z₄ symmetry has been proposed. In this model, certain particles are endowed with unique properties, and it shows how muons and tau particles can interact via Higgs particles. In this presentation, I will discuss the features of this model and how its predictions can be experimentally verified.