Abstract
We investigate the spectrum of the
automorphic Laplace-Beltrami operator on discrete quotients of
complex hyperbolic space. This is a joint work with Peter Lax. Let
$\Gamma$ be a geometrically finite,
discrete subgroup of holomorphic isometries of the complex hyperbolic
space. We assume that the
fundamental domain is noncompact, has finite complex hyperbolic volume.
The fundamental domain
is allowed to have finitely many cusps of maximal rank. Under these
assumptions, we prove that the
spectrum of the automorphic Laplace-Beltrami operator consists of the
union of a standard point
spectrum and an absolutely continuous part of uniform multiplicity,
which is equal to the interval
$(-\infty, -n^{2}/4)$. The uniform multiplicity of the absolutely continuous
part of the spectrum
is equal to the number of cusps of maximal rank.