We study the evolution of topological defects in multi-axion models and propose a novel solution to the domain wall problem of the QCD axion.
Multi-axion dynamics, arising from multiple Peccei–Quinn scalars, can lead to qualitatively different defect evolution compared to single-axion models. In particular, networks of cosmic strings and high-tension domain walls tend to form, posing a...
The interplay between wave-like dark matter and Earth’s conductive properties generates a global monochromatic magnetic field. Simple experimental setups, such as those pioneered by the SNIPE Hunt collaboration, have already demonstrated the feasibility of probing axion-like particles and dark photons. Beyond these candidates, this approach can also be extended to ultralight dark matter...
The James Webb Space Telescope (JWST) observations have identified a class of compact galaxies at high redshifts (4 \lesssim z \lesssim 11), dubbed "little red dots" (LRDs). The supermassive black holes (SMBHs) of 10^{5-8}{\rm\,M}_{\odot} in LRDs favor a heavy-seed origin. We propose a mechanism for their formation: Clusters of primordial black holes, formed through long-short mode coupling on...
Axion is one of the well-motivated candidates for dark matter and there have been many attempts for axion dark matter search. In this talk, we show novel aspects of the axion dark matter, which significantly modify the physics of vortex in the Abelian-Higgs model. Due to the axion-photon conversion, electromagnetic fields are induced in the magnetic core of the vortex. In numerical...
We investigate a cogenesis scenario for composite asymmetric dark matter framework: a dark sector has a similar strong dynamics to quantum chromodynamics in the standard model, and the dark-sector counterpart of baryons is the dark matter candidate. The Hawking evaporation of primordial black holes plays a role of a source of heavy scalar particles whose $CP$-violating decay into quarks and...
In this talk, we discuss triple $Z'$ boson signals via the decay chain of $Z \to Z' \phi \to Z' Z' Z'$, with a new light scalar $\phi$, at future Z factories such as CEPC and FCC-ee. These new bosons $\phi$ and $Z'$ naturally appear in models with a new $U(1)$ gauge symmetry which is spontaneously broken and introduced in various new physics scenarios. The branching ratio of $Z \to Z' \phi \to...
The 2HDM+S is the singlet extension of the Two-Higgs-Doublets Model (2HDM). The singlet field and its mixing with the 2HDM Higgs sector lead to new contributions to the electroweak precision observables, in particular, the oblique parameters. In this paper, we identify five benchmark cases, where at most one mixing angle is nonzero and analyze the 95\% C.L. allowed parameter space by the...
Based on the general principles of Lorentz symmetry and unitary, we introduce two consistency conditions -- on-shell gauge symmetry and strong massive-massless continuation -- in constructing amplitudes of massive gauge theory with elementary particles. Combined with the little group transformation and consistent factorization, we construct 3-point and 4-point vector boson/scalar...
In this presentation, we discuss a relation between the dynamics of the ElectroWeak Phase Transition (EWPT) and the entanglement entropy defined in scattering processes. As a representative scenario, we focus on the SM extension with N singlet scalar fields with the global O(N) symmetry. We also discuss a possibility that the entanglement entropy may be used as an order parameter for the EWPT....
Selection rules are fundamental principles in quantum systems and quantum field theory, determining whether certain couplings are allowed or forbidden. Conventionally, selection rules are associated with conservation laws originating from a certain group-like symmetry. However, it has been found that non-invertible selection rules also appear in quantum field theory and string theory. In this...
The strong CP problem remains one of the most significant unresolved issues in the Standard Model. A promising approach is to assume that CP is an exact symmetry of the Lagrangian, broken spontaneously by the vacuum. Supersymmetry (SUSY) provides a natural framework for such scenario, offering both protection of hierarchies and flat directions where spontaneous CP violation (SCPV) can occur....
If the nano-Hz gravitational wave signal observed by Pulsar Timing Array (PTA) experiments originates from a strongly supercooled first-order phase transition, the resulting supercooling at ${\cal O}(1)$ GeV temperature necessitates a new mechanism for generating the baryon asymmetry and dark matter, as any pre-existing abundances are diluted. We propose a model of cold darkogenesis, where the...
The present talk will cover an extension of a scotogenic and its modular $\mathcal{A}_4$ variation a step forward and demonstrates scotogenic modular $\mathcal{A}_4$ non-supersymmetric realization. To achieve this non-holomorphic modular symmetries come to rescue. Advantage of the current construction is the compactness of the model content and absence of the supersymmetric fields. Neutrino...
We investigate the complex singlet extension of the Standard Model, which provides a pseudo-Nambu-Goldstone dark matter candidate. In addition to the latest and most stringent bounds from dark matter direct detection experiment, we impose the observed DM relic abundance and a novel condition that the imaginary component of the singlet field does not develop a vacuum expectation value, ensuring...
