A neutrino rest mass _might_ make cosmic expansion evenmtually stop & reverse,
leading to a "big crunch". But to get from there to an oscillating universe is harder.
It would require first some process to cause the universe to "bounce" at some minimum
size. Then you would have to contend with the effect which Tolman discovered in the
30s, that such a bouncing universe will actually _grow_ in size on each bounce. It is
conceivable that this could be avoided if the parameters characterizing the universe
were appropriately reset in each bounce but there is no good reason to think that this
George L. Murphy