Strong Lensing Constraints on Small-Scale Linear Power
  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. 
Neal Dalal, Christopher S. Kochanek