Small gaps in the spectrum of the rectangular billiard

Eigenfunctions for partially rectangular billiards

In this note we further develop the idea of using a ``black box'' point of view (see our previous work) to study eigenfunctions for billiards which have rectangular components: they include the Bunimovich billiard, the Sinai billiard, and the recently popular pseudointegrable billiards

Nonconcentration of eigenfunctions for partially rectangular billiards

In this paper, the results of Burq and Zworski are further developed to study nonconcentration of eigenfunctions for billiards which have rectangular components: these include the Buminovich billiard, the Sinai billiard, and certain pseudointegrable billiards. The results presented are an application of using a "black box" point of view as presented by the same authors.

Nonconcentration in partially rectangular billiards

In specific types of partially rectangular billiards we estimate the mass of an eigenfunction of energy $E$ in the region outside the rectangular set in the high-energy limit. We use the adiabatic ansatz to compare the Dirichlet energy form with a second quadratic form for which separation of variables applies. This allows us to use sharp one-dimensional control estimates and to derive the bound assuming that $E$ is not resonating with the Dirichlet spectrum of the rectangular part.

Ergodic billiards that are not quantum unique ergodic

Partially rectangular domains are compact two-dimensional Riemannian manifolds $X$, either closed or with boundary, that contain a flat rectangle or cylinder. In this paper we are interested in partially rectangular domains with ergodic billiard flow; examples are the Bunimovich stadium, the Sinai billiard or Donnelly surfaces. We consider a one-parameter family $X_t$ of such domains parametrized by the aspect ratio $t$ of their rectangular part. There is convincing theoretical and numerical evidence that the Laplacian on $X_t$ with Dirichlet or Neumann boundary conditions is not quantum uniqu…

A non-concentration estimate for partially rectangular billiards

We consider quasimodes on planar domains with a partially rectangular boundary. We prove that for any $ε_0>0$, an $Ø(λ^{-ε_0})$ quasimode must have $L^2$ mass in the "wings" bounded below by $λ^{-2-δ}$ for any $δ>0$. The proof uses the author's recent work on 0-Gevrey smooth domains to approximate quasimodes on $C^{1,1}$ domains. There is an improvement for $C^{2,α}$ domains.

平方和间隙的泊松分布与环形点散射器的能级间距

Poisson distribution for gaps between sums of two squares and level spacings for toral point scatterers

本文研究了平方和间隙的泊松分布，并证明了环形点散射器的能级间距在弱耦合极限下也服从泊松分布。