As part of a programme in which quantum state reduction is understood
as a gravitational phenomenon, we consider the Schrodinger-Newton equa
tions. For a single particle, this is a coupled system consisting of t
he Schrodinger equation for the particle moving in its own gravitation
al field, where this is generated by its own probability density via t
he Poisson equation. Restricting to the spherically-symmetric case, we
find numerical evidence for a discrete family of solutions, everywher
e regular, and with normalizable wavefunctions. The solutions are labe
lled by the non-negative integers, the nth solution having n zeros in
the wavefunction. Furthermore, these are the only globally defined sol
utions. Analytical supper? is provided for some of the features found
numerically.