Evading Thermalization: Fragmentation and Caging in Many-Body Hilbert Space

by Frank Pollmann

Thursday Nov 20, 2025, 2:15 PM → 3:45 PM Europe/Berlin

D5-153 (UHG)

Thermalization in isolated quantum systems is typically explained by the eigenstate thermalization hypothesis (ETH), yet several mechanisms are known to cause its breakdown. I will discuss two such scenarios in systems with constrained dynamics. First, we show that constraints can fragment the Hilbert space into exponentially many disconnected sectors, leading to persistent non-ergodic behavior. Second, we demonstrate that destructive interference can confine dynamics within “Fock space cages,” giving rise to localized many-body states—generalizing the concept of Aharonov-Bohm Cages to the realm of many-body physics. 

Seminar Condensed Pollmann.pdf