1. Axions

Axions have the potential to address several key limitations of the Standard Model (SM). They offer solutions to the strong-CP problem, serve as an excellent candidate for cold dark matter, and help explain the matter-antimatter asymmetry of the universe. In certain specific models, axions also address the hierarchy problem within the SM. Motivated by these possibilities, extensive searches for axions are being conducted across all fundamental frontiers. My current research focuses on the following aspects related to axions:

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• Renormalization schemes in axion EFT: We formulated axion effective field theory within the BMHV scheme, analyzing the renormalization of fermionic dimension-five operators. Employing Ward identities for chiral currents, we determined the required finite renormalization factors and clarified the role of evanescent operators in maintaining consistency of the theory (arXiv: 2603.26880).

• Effective field theory of axions and searches at the intensity frontier : We investigated the B→Ka transition as a powerful probe of heavy QCD axions, conducting necessary two-loop calculations (arXiv: 2102.04474), identifying all relevant counterterms, anomalous dimension matrix and the cancellation of IR divergences is explicitly demonstrated (arXiv: 2412.09678). We also explored the phenomenological implications of this transition at flavor factories (arXiv: 2108.10331).

• Astrophysical implications of axions: We highlighted that, in addition to prototypical interactions, axions can also possess Wess-Zumino-Witten (WZW) terms, which introduce a coupling between axions, photons, and vector mesons. These interactions can lead to the photo-production of axions in nucleon-rich stellar objects as well as in terrestrial experiments (arXiv: 2403.12169,).

• Cosmological implications of axions: We explored a chiral gauge theory in which light composite Dirac neutrinos dynamically emerge, complemented by a QCD axion to address the strong CP problem. We demonstrated that the interplay between the composite sector and the axion can simultaneously achieve successful baryogenesis and generate the correct dark matter abundance through a mechanism, known as "co-genesis" (arXiv: 2108.04293).

2. Model of Mesons

Mesons provide an important laboratory for probing strong interactions and searching for physics beyond the Standard Model. Owing to the interplay of perturbative and non-perturbative QCD effects, heavy–light meson systems such as B and D mesons are particularly well suited for effective field theory techniques. My research focuses on the dynamics of mesons within frameworks such as HQET, SCET, and chiral perturbation theory, with applications to flavor physics and precision studies at the intensity frontier.

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• Framework for Heavy Light Pseudoscalar Mesons: We develop a symmetry-guided model of pseudoscalar mesons to study charged-current weak decays of heavy-light mesons. The framework combines chiral symmetry in the light sector with heavy-quark flavor symmetry, while CKM elements are incorporated as spurions. It organizes the leading dimension-six current-current operators relevant for leptonic, semileptonic, and hadronic decays, reproduces known heavy-quark scaling relations, and provides a hadron-level description of non-factorizable effects. (arXiv: 2605.26880).

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3. FOPT

Generic gauge theories utilize phase transitions to induce masses for particles through spontaneous symmetry breaking. First-order phase transitions (FOPT) have garnered significant attention recently for two principal reasons. Firstly, FOPT signify a departure from thermal equilibrium, which is crucial for elucidating baryogenesis. Secondly, the physics associated with FOPT can be probed across various frontiers, including within the gravitational wave spectrum. Our recent contributions have encompassed the following areas:

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• Ultra-relativistic bubbles in SM with a real singlet scalar field: We conducted an analysis of phase transitions within the minimal extension of the Standard Model incorporating a real singlet scalar field. Our study innovatively focused on identifying and comprehensively examining the parameter space region conducive to first-order phase transitions (FOPT). Specifically, we investigated scenarios where bubbles containing the true vacuum can attain relativistic velocities. This particular parameter regime holds significant interest due to its potential implications for novel baryogenesis and dark matter production mechanisms recently under discussion (arXiv: 2207.02230).

• Ultra-relativistic bubbles in SMEFT: In this study, we extend our analysis using a model-independent approach within the framework of the Standard Model Effective Field Theory (SMEFT) incorporating dimension-6 and dimension-8 operators. We utilize a thermally corrected and renormalization group improved potential to examine its impact on the nucleation temperature. Subsequently, we outline the dynamics of bubble formation leading to ultra-relativistic bubble wall velocities, primarily motivated by the implications for gravitational wave detection. We emphasize the ranges of the Wilson coefficients that result in such bubble wall velocities and predict the gravitational wave spectra generated by these phase transitions, which can be tested in future experimental observations (arXiv:2402.02914).

4. SCET for Gravity

We have investigated two significant topics in the context of soft collinear effective theory (SCET) for gravitational interactions. First, we have extended the collinear Wilson lines, which are essential for maintaining multiple copies of diffeomorphism invariance in gravity SCET, to all orders in the SCET expansion parameter λ. Previously, these had only been understood up to O(λ) in the literature. Second, we have analyzed the implications of reparametrization invariance (RPI) for the structure of gravity SCET Lagrangians. To demonstrate the utility of RPI, we present an explicit example where the O(λ²) hard interactions of a collinear graviton are entirely predicted by RPI from its O(λ) hard interactions. Furthermore, we highlight that the combined requirements of multiple diffeomorphism invariances and RPI impose specific relations among the O(λ) terms. This reduces the number of O(λ) terms that need to be determined by matching onto the full theory initially (arXiv:1910.10738).