I'm attempting to find solutions to the dark matter and hierarchy problems. My research mostly focuses on the Higgs sector's extensions. I take a bottom-up and top-down approach to it.

To search for scalar sectors in a model-independent manner, the EFT approach is quite useful. However, EFT has ambiguities in its basis choice. In order to extract truly physical information from EFT, we focus on the target space of the scalar sector (the internal space when the scalar field is thought of as a coordinate axis) and study its geometry to describe physical observables. We have extended the geometrical approach to not only scalar sectors but also sectors involving fermions, such as Yukawa terms, and have succeeded in expressing physical quantities in a covariant manner.

A promising candidate for dark matter is the Weakly Interacting Massive Particle (WIMP). However, WIMP is severely constrained by direct detection experiments. By extending the scalar sector, I am aiming to find a solution to this issue. My study primarily focuses on the pseudo-Nambu-Goldstone Dark Matter (pNGB DM) model, which can correctly reproduce the DM relic abundance without subjecting itself to rigorous experimental constraints. By including the pNGB DM in a non-abelian gauge symmetric model, we have successfully stabilized pNGB DM. I am currently working on embedding that model in a grand unified theory.

I also focus on non-thermal dark matter production and study a model that produces sterile neutrino dark matter in a freeze-in mechanism. We consider B-L gauge symmetry and take into account the influence of scalar fields that give mass to the B-L gauge fields, which has not been properly addressed in previous studies.

Consideration of a compactified extra-dimension in addition to the four dimensions of spacetime we are aware of is one of the models for resolving the hierarchy problem. Recently, it has been shown that introducing a background field in the extra dimension causes cancellation among quantum corrections to the scalar field mass, bringing us one step closer to solving the hierarchy problem. The scalar field, however, is still massless and cannot be connected to the Higgs boson. We are studying the proper introduction of scalar field mass in order to identify it as the Higgs boson.