(Welcome Seminar) The Wave Nature of (self-interacting) Ultralight Dark Matter in Galactic-Scale Dynamics

• Hyeonmo Koo (IBS CTPU-PTC)

Room: B438 Ultralight dark matter (ULDM), characterized by a scalar field with a mass of O(1e-22~1e-21 eV), exhibits a macroscopic de Broglie wavelength on the order of kiloparsecs. This gives rise to wave-like phenomena at galactic scales, such as rapid relaxation and the suppression of dynamical friction. In this talk, I will summarize my research achievements during my doctoral studies concerning these wave-like properties. Time permitting, I will also discuss my current research interests and future directions at IBS.

Bipartite Solution to the Lithium Problem

• Sougata Ganguly (IBS CTPU-PTC)

Room: B438 The primordial lithium problem remains a persistent motivation for new-physics modifications of Big Bang Nucleosynthesis (BBN). At the same time, the precise measurement of primordial deuterium abundance places strong constraints on such scenarios. Therefore, the central challenge is to reduce the predicted ${}^7 Li$ while remaining consistent with the deuterium observations. In this talk, we will discuss a possible solution to the lithium problem in a bipartite framework. In the first stage, we consider a majoron which dominantly decays into the Standard Model (SM) neutrinos while in the second stage we consider an axion-like particle (ALP)  which decays into photon pairs. Although our setup is model-dependent, it provides an explicit proof of concept demonstrating that the lithium abundance can be reduced consistently with current deuterium constraints.

Circumstellar Medium of Supernovae as New Probes for Feebly-interacting Particles

• Chui-Fan Kong (IBS CTPU-PTC)

Room: B438 We propose a new observational strategy to probe feebly interacting particles (FIPs) using dense, confined circumstellar material (CSM) around core-collapse supernovae. FIPs produced in the proto–neutron star can decay outside the star but still within the CSM prior to shock breakout, depositing visible energy that heats and ionizes the surrounding medium and forms a FIP-induced photosphere. This can generate a distinctive early-time precursor signal, approximately thermal (blackbody-like), that is complementary to conventional supernova cooling constraints. In this talk, I will present the underlying mechanism, characterize the expected precursor emission, and discuss how early-time supernova observations can be used to search for or constrain FIP scenarios.

Resonant Scattering in Two-Flavoured Sp(4) Lattice Gauge Theories

• Jong-Wan Lee (Institute for Basic Science (IBS))

Room: B438 In this talk, we consider Sp(4) gauge theory coupled to two fundamental Dirac fermions. This theory provides a microscopic realization of the strongly interacting massive particles (SIMPs) scenario for dark matter, as well as that of the composite Higgs scenario. Using numerical lattice simulations, we perform non-perturbative studies of pseudoscalar scattering and vector resonance. In particular, we compute the finite-volume spectrum of the composite states interpolated by both vector and two-pseudoscalar operators, and employ Luscher's method to extract properties of the infinite-volume scattering process in the 10-plets of the unbroken Sp(4) group. We present our findings for the cases with large, moderate, and relatively small fermion masses, and discuss their implications for dark matter phenomenology.

Digital Quantum Simulation for Energy Spectroscopy: Schwinger and Ising Model

• Dongwook Ghim (IBS CTPU-PTC)

Room: B438 Recent advances in quantum computation offer a promising path to explore quantum field theories, circumventing the sign problem inherent in classical Monte Carlo methods. As an example of such an application, this talk will introduce a novel quantum algorithm for energy spectroscopy, directly inspired by the 'coherent imaging' technique demonstrated by C. Senko et al. (2014). The proposed method extracts the excited-state energy spectrum by applying a periodically oscillating perturbation (quench) to the ground state and by identifying the resonance frequencies where the vacuum-to-vacuum probability drops significantly after the quench. This talk demonstrates how this intuitive spectroscopy approach is naturally implemented in digital quantum simulation. I will use the (1+1)-dimensional Schwinger model with a topological term and the Ising model on a periodic chain as explicit examples. The talk will discuss the computational efficiency and practical implications of this algorithm in the upcoming era of early fault-tolerant quantum computers.

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• CTPU-PTC Members

Room: B438