Dark matter is one of the biggest mysteries in physics and astronomy today. While multiple dark matter candidates have been proposed, such as the axion and primordial black holes (PBHs), the interplay between them is not well understood. In this talk, I will focus on the formation of axion minihalos around PBHs and the condensation of axion stars inside them, and reveal distinct morphological...
Cosmic strings, theoretical one-dimensional topological defects from the early universe, are a compelling source for studying dark matter production and gravitational wave (GW) emission. In this talk, I will focus on the production of gauge bosons and GW emission resulting from the decay of cosmic strings, discussing the constraints imposed by cosmological considerations. Specifically, I will...
We perform an analytic calculation of binary star evaporation rate under the gravitational potential from spatially extended dark solitons, and demonstrate that Milky Way’s wide binary star systems are susceptible to tidal perturbations from dark matter solitons of comparable and larger sizes. The GAIA data shows a sharp decrease of halo-like wide binaries at large separations, indicating...
Combination of recent measurements for $h \to Z \gamma$ from ALTLAS and CMS shows an excess that the ratio of the observed and standard model (SM) predicted branching ratios $\mu = (\sigma\cdot{\cal B})_{\mathrm{obs}}/(\sigma\cdot{\cal B})_{\mathrm{SM}}$ is $2.2\pm 0.7$. If confirmed, it is a signal of new physics (NP) beyond SM. We study NP explanation for this excess. In general, for a...
The 2HDM+S is the singlet extension of 2HDM, which can accommodate more physics potential beyond the SM. We summarize the type II 2HDM+S model with various Higgs potential structures, and discuss several scenarios with different mass hierarchy. In this study, we concentrate on the mass eigenstate of the 2HDM+S, and test the parameter space of Higgs mixing angles and masses against the...
Ultra-light Dark Matter (ULDM) is one of the most promising DM candidates. Due to the Bose
enhancement, we find the annihilation rate of the ULDM in the presence of background photon
radiation can be greatly enhanced and produce a distinctive reflected electromagnetic wave with an
angular frequency equal to the ULDM mass. We propose to utilize such stimulated annihilation
to probe the ULDM...
Future observation with next-generation large-area radio telescopes are expected to discover radio pulsars closely orbiting around Sagittarius A (Sgr A), the supermassive black hole (SMBH) in our Galactic Center (GC). Such a system can provide a unique laboratory for testing gravity theories , as well as the astrophysics around the GC. We will introduce our recent studies about prospects for...
Spherical black-hole (BH) solutions have been found in the bumblebee gravity where a vector field nonminimally couples to the Ricci tensor. We study dynamic (in)stability associated with the gravitational and vector perturbations of odd parity against these bumblebee BHs. Under the plane-wave approximation, we find that bumblebee BHs do not suffer ghost instability, but gradient instability...
We explore the theoretical description of oscillations in degenerate cases, presenting the formula for oscillation probability with neutrino oscillation as an illustrative example. We then apply the degenerate oscillation theory to study neutron-antineutron oscillations, calculating the constraints of the new model on oscillation parameters, such as mixing angles, in neutron stars. Our...
High-energy muon collider can play as an emitter of electroweak gauge bosons and thus leads to substantial vector boson scattering (VBS) processes. In this work, we investigate the production of heavy neutral lepton (HNL) $N$ and lepton number violation (LNV) signature through VBS at high-energy muon colliders. They provide clean and robust LNV signatures to tell the nature of Majorana HNLs...
Considering the hierarchical structure of fermionic masses and the fermionic flavor mixing puzzles in the Standard Model, we propose to relate them by the see-saw mechanism, i.e. only the third generation of quarks and charged leptons achieve the masses at the tree level, the first two generations achieves masses through the mixings with the third generation, and the neutrinos achieve tiny...
The Witten effect implies the dynamics of axion and magnetic monopole. The Cho-Maison monopole is a realistic electroweak monopole arisen in the Weinberg-Salam theory. This monopole of TeV scale mass motivates the dedicated search for electroweak monopole at colliders. In this work we investigate the implication of KSVZ axion to the electroweak magnetic monopole. We use the spherically...
In this talk, we will discuss production of gravitational waves in the early universe within a first order phase transition involving a hidden sector feebly coupled with the visible sector. Unlike most existing studies on GWs from hidden sectors, which assume a constant temperature ratio between the hidden and visible sectors (i.e., ξ=T_h/T=const), we adopt a more precise approach using...
