13.10.2026 Thea Budde (ETH Zurich)
Location: HIT E 41.1, Time: 12:00
Ergodicity breaking from unconventional lattice symmetry
Statistical physics rests on the assumption that many-body systems uniformly explore all available states. The model is only constrained by its symmetries, which are sufficient to predict its long-time behavior. This raises the question of what counts as a symmetry. Traditional notions of symmetry rely on quantities with a straightforward analog in relativistic continuum theories. However, there are broader classes of conserved quantities on the lattice for which this is not the case, such as subsystem symmetries and partial isometries. These can explain why several models seem to break ergodicity and fail to thermalize as was expected when only traditional symmetries are considered. In this talk, I will present examples of models with quantum many-body scars and Hilbert space fragmentation, whose behavior was previously classified as ergodicity breaking, but can instead be explained by unconventional symmetries. These results raise two questions: does all ergodicity breaking originate in unconventional conserved quantities, and what would be a useful classification of lattice conserved quantities in this context?