Vivek Singh (TIFR, Mumbai), Emergent semiclassicality in the Krylov basis

Tuesday 15 Sept 2026, 11:15 → 12:30 Europe/Stockholm

Albano 3: 6228 - Mega (22 seats) (Albano Building 3)

Title: Emergent semiclassicality in the Krylov basis

Abstract: What does it mean for quantum dynamics to be classical or semi-classical? In this talk, I will start with the observation that Wigner negativity measures the complexity of classically simulating the preparation of a state, and its time growth is minimized in the Krylov basis. Thus, one can identify dynamics as being classical if its negativity saturates in the Krylov basis as time increases, and semiclassical if the negativity growth does not scale with system size. I will demonstrate these ideas in 2d CFTs, Random Matrix theories and the double-scaled SYK model. In all these examples, at large but O(1) times, Wigner negativity remains constant or grows slowly, demonstrating an emergent semi-classicality of dynamics in the Krylov basis even if the wavefunction spreads rapidly across the Krylov basis. Along the way, I will also discuss the implications of these results in holography.