  We place limits on the linear power spectrum on small scales (k > 50 h/Mpc)
using measurements of substructure in gravitational lens galaxies. We find
excellent agreement with the simplest LambdaCDM models, and in conjunction with
other cosmological probes, place constraints on the neutrino mass m_nu, tilt of
the primordial power spectrum n, and mass of the dark matter particle m. We
find n>0.94, and for a Harrison-Zeldovich spectrum, find m_nu<0.74 eV and m>5.2
keV, at 95% confidence.
