This is the first survey of highly excited eigenstates of a chaotic 3D
billiard. We introduce a strongly chaotic 3D billiard with a smooth boundary
and we manage to calculate accurate eigenstates with sequential number (of a
48-fold desymmetrized billiard) about 45,000. Besides the brute-force
calculation of 3D wavefunctions we propose and illustrate another two
representations of eigenstates of quantum 3D billiards: (i) normal derivative
of a wavefunction over the boundary surface, and (ii) ray - angular momentum
representation. The majority of eigenstates is found to be more or less
uniformly extended over the entire energy surface, as expected, but there is
also a fraction of strongly localized - scarred eigenstates which are localized
either (i) on to classical periodic orbits or (ii) on to planes which carry
(2+2)-dim classically invariant manifolds, although the classical dynamics is
strongly chaotic and non-diffusive.Comment: 12 pages in plain Latex (5 figures in PCL format available upon
request) Submitted to Phys.Lett.