  It has been shown by many independent studies that the cold dark matter
scenario produces singular galactic dark halos, in strong contrast with
observations. Possible remedies are that either the dark matter is warm so that
it has significant thermal motion or that the dark matter has strong self
interactions. We have combined these ideas to calculate the linear mass power
spectrum and the spectrum of cosmic microwave background (CMB) fluctuations for
self-interacting warm dark matter. Our results indicate that such models have
more power on small scales than is the case for the standard warm dark matter
model, with a CMB fluctuation spectrum which is nearly indistinguishable from
standard cold dark matter. This enhanced small-scale power may provide better
agreement with the observations than does standard warm dark matter.
