Maciej Zworski (UC Berkeley)
Optimal enhanced dissipation for geodesic flow
Abstract:
We consider geodesic flows on negatively curved compact
manifolds or more generally contact Anosov flows (all these concepts
will be explained). The object is to show that if X is the
generator of the flow and Δ, a (negative) Laplacian, then
solutions to the convection diffusion equation, ∂t u = X u
+ Δu, u ≥ 0, satisfy
∥ u(t) - u ∥L²(M) ≤ C
u-K e-βt ∥ u(0)∥L²(M)
,
where u is the (conserved) average of u(0) with
respect to the contact volume form and K is a fixed constant. This
provides many examples of very precise optimal enhanced
dissipation in the sense of recent works of
Bedrossian–Blumenthal–Punshon-Smith and Elgindi–Liss–Mattingly. The
proof is based on results by Dyatlov and the speaker on stochastic
stability of Pollicott‐Ruelle resonances, another concept which will
be introduced and explained. The talk is based on joint work with
Zhongkai Tao.