This work concerns
norms of high energy Laplace eigenfunctions:
,
.
Sogge (1988) gave optimal estimates on the growth of
for a general compact Riemannian manifold. Here we give general
dynamical conditions guaranteeing quantitative improvements
in estimates
for , where
is the
critical exponent. We also apply results of an earlier paper (Canzani and Galkowski 2018)
to obtain quantitative improvements in concrete geometric settings including all product
manifolds. These are the first results giving quantitative improvements for estimates on
the
growth of eigenfunctions that only require dynamical assumptions. In contrast with
previous improvements, our assumptions are local in the sense that they depend only
on the geodesics passing through a shrinking neighborhood of a given set in
. Moreover,
we give a structure theorem for eigenfunctions which saturate the quantitatively improved
bound. Modulo an error, the theorem describes these eigenfunctions as finite sums of
quasimodes which, roughly, approximate zonal harmonics on the sphere scaled
by .
Keywords
Eigenfunctions, high energy, $L^p$ norms, microlocal,
second microlocal