Welcome

• Chia-Min Chung (NYCU)

Room: General Building III/Room-512 - Meeting

Classical Spin–Orbital Kitaev Models from Rydberg Atom Arrays

• Fabrizio Oliviero (NCTS)

Room: General Building III/Room-512 - Meeting We investigate an exactly solvable spin-orbital model that serves as a classical analogue of the celebrated Kitaev honeycomb model, describing interacting Rydberg atoms on the ruby lattice. Exploiting both its local and nonlocal symmetries, we derive the exact partition function and the static structure factor. A mapping between $S=3/2$ models on the honeycomb lattice and kagome spin Hamiltonians enables us to interpret its thermodynamic properties in terms of a classical kagome spin ice. By partially breaking the symmetries associated with line operators, we uncover a model hosting immobile excitations—classical fractons—alongside a ground-state degeneracy that grows exponentially with system length. Finally, we construct a continuum description that reveals the underlying gauge structure and conserved charges, and discuss extensions of our framework to other lattices and higher-spin systems.

Duality and quantum many-body scars

• Weslei Fontana (NTHU)

Room: General Building III/Room-512 - Meeting Dualities have long been a powerful way to understand quantum many-body systems, especially when perturbative methods fail. More recently, they’ve even been reinterpreted as generalized symmetries, which can strongly constrain the low-energy description and guarantee that the ground state is non-trivial. In this talk, I’ll show how duality can also play a role in non-equilibrium setups, focusing on quantum many-body scars (QMBS) — special eigenstates of chaotic Hamiltonians that refuse to thermalize. Duality gives us two things: first, a way to generate new examples of QMBS, and second, a way to understand their robustness — when they really behave as non-thermal states, and when they don’t. To make these ideas concrete, I’ll walk through a simple 1+1D spin chain related by Kramers–Wannier duality, and show that while QMBS may show up at first, their behavior can change completely once we introduce a dual perturbation.

Accelerating GW calculations via Machine Learning: Predicting Quasiparticle energies with Minimal Training

• Ragab Abdelghany (National Chung Hsing University)

Room: General Building III/Room-512 - Meeting Accurate GW quasiparticle energy calculations are essential for understanding excited-state electronic properties in materials but remain prohibitively expensive for large-scale or dynamic simulations. We introduce a machine learning framework that predicts G₀W₀ quasiparticle energies across molecular dynamics (MD) trajectories with high accuracy using only mean-field eigenvalues and exchange–correlation potentials from density functional theory. Trained on just 25% of MD snapshots for silicon and boron nitride, the model achieves root-mean-square errors below 0.1 eV and reproduces k-resolved band structures and densities of states, including for boron nitride polymorphs excluded from training. This approach eliminates the need for costly dielectric-matrix calculations, reducing prediction times from hours to seconds per snapshot while maintaining many-body accuracy. The method provides a scalable route for excited-state electronic structure simulations in dynamically evolving environments and enables rapid exploration of novel materials with GW-level precision.

RG in CFTs or domain wall in TQFTs is ring homomorphism: Generalizing Moore-Seiberg data

• Fukusumi Yoshiki (NTU)

Room: General Building III/Room-512 - Meeting Classification of topological quantum field theories (or topological order in condensed matter) is one of the most fundamental problems in recent theoretical research (and experimental research to some extent). Recently, this problem has been analyzed by considering the domain wall problem between different TQFTs. Applying the correspondence between conformal field theory (CFT) and TQFT, the corresponding problem on the CFT side is the classification of the massless renormalization group (RG) between CFTs by Zamolodchikov or the RG domain wall by Gaiotto. In this talk, we demonstrate that a general class of these domain wall problems can be solved by generalizing the method of integer spin simple current by Schellekens and Gato-Rivera. We provide general construction of unfamiliar (hopefully new) types of modular invariants and the resultant domain walls. Whereas the Moore-Seiberg data provides the ring isomorphism from one full CFT to the chiral CFT, our formalism provides a ring homomorphism from one full CFT to other CFTs. Hence, our formalism is a natural extension of the Moore-Seiberg data. This talk is based on the recent preprint arXiv:2412.19577.

Magnetic effects of non-magnetic impurities in gapped short-range resonating valence bond spin liquids

• Zahid Ansari (NYCU)

Room: General Building III/Room-512 - Meeting We study the effect of a small density nv of quenched non-magnetic impurities, i.e. vacancy disorder, in gapped short-range resonating valence bond (RVB) spin liquid states and valence bond solid (VBS) states of quantum magnets. We argue that a large class of short-range RVB liquids are stable at small nv on the kagome lattice, while the corresponding states on triangular, square, and honeycomb lattices are unstable at any nonzero nv due to the presence of emergent vacancy-induced local moments. In contrast, VBS states are argued to be generically unstable (independent of lattice geometry) at nonzero nv due to such a local-moment instability. Our arguments rely in part on an analysis of the statistical mechanics of maximally-packed dimer covers of the diluted lattice, and are fully supported by our computational results on O(N) symmetric designer Hamiltonians. [In collaboration with Prof. Kedar Damle, PRL, 132, (2024), 226504]

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