Suppose $M$ is a closed Riemannian manifold with an orthonormal basis $B$
of $L^2(M)$ consisting of Laplace eigenfunctions. A classical result of
Shnirelman and others proves that if the geodesic flow on the cotangent
bundle of $M$ is ergodic, then $M$ is quantum ergodic, in particular, on
average, the probability measures defined by the functions $f$ in $B$ on $M$
tends on average towards the Riemannian measure on $M$ in the high
energy limit (i.e, as the Laplace eigenvalues of $f \to \infty$).
We now want to look at a level aspect of this property, namely, instead
of taking a fixed manifold and high energy eigenfunctions, we take a
sequence of Benjamini-Schramm convergent compact Riemannian manifolds
$M_j$ together with Laplace eigenfunctions $f$ whose eigenvalue varies in
short intervals. This perspective has been recently studied in the
context of graphs by Anantharaman and Le Masson, and for hyperbolic
surfaces and manifolds by Abert, Bergeron, Le Masson, and Sahlsten. In
my talk I want to discuss joint work with F. Brumley in which we study
this question in higher rank, namely sequences of compact quotients of
This talk is part of the online Number Theory Web Seminar, and will be streamed live on Zoom.
To attend the talks, registration is necessary. To register please visit our website
Registered users will receive an email before each talk with a link to the Zoom meeting.
Mike Bennett (University of British Columbia)
Philipp Habegger (University of Basel)
Alina Ostafe (UNSW Sydney)