Let
be a potential on ℜ
that is smooth everywhere except at
a discrete set
S of points, where it has singularities of the
form
, with
for
close to
and
continuous on ℜ
with
for
p ∈ S. Also assume
that
and
are smooth outside
S and
is smooth in
polar coordinates around each singular point. We either assume that
is periodic or that the set
S is finite and
extends to a
smooth function on the radial compactification of ℜ
that is
bounded outside a compact set containing
S. In the periodic case,
we let
be the periodicity lattice and define
T: = ℜ
3/Λ. We obtain regularity results in weighted Sobolev space for
the eigenfunctions of the Schrödinger-type operator
acting on
L2(
T), as well as for the induced
-Hamiltonians
Hk obtained by restricting the action of
to
Bloch waves. Under some additional assumptions, we extend these
regularity and solvability results to the non-periodic case. We sketch
some applications to approximation of eigenfunctions and eigenvalues
that will be studied in more detail in a second paper.