The large-order behavior of the Floquet-Magnus expansion encodes the heating rate
Dylan Z. Liu Liu
Abstract
Driven many-body systems heat at a rate Γ that falls steeply with the drive frequency ω, and their Floquet-Magnus expansion is asymptotic. We compute the expansion exactly in the thermodynamic limit to order 37 for strongly driven spin chains and compare its large-order growth with exact heating rates. The superasymptotic exponent of its energy component reproduces κ = -d ln Γ/dω within 17% in two models; operator norms, as used in rigorous bounds, miss it by factors of 1.2–2.2. In linear response this is a Bender-Wu relation: the energy coefficients are moments of the absorption spectrum.