Can Dark Matter explain the Braking Index of Neutron Stars?
  We explore a new mechanism of slowing down the rotation of neutron stars via accretion of millicharged dark matter.   We find that this mechanism yields pulsar braking indices that can be substantially smaller than the standard $n\sim 3$ of the magnetic dipole radiation model for millicharged dark matter particles that are not excluded by existing experimental constraints thus accommodating existing observations. 
Chris Kouvaris and M. Angeles Perez-Garcia
astro-ph.SR hep-ph