In collaboration with S. Gandolfi (LANL), I combined neutron star mass and radius observations with recent results from quantum Monte Carlo on the equation of state of neutron matter to obtain: limits on the strength of three-neutron forces, the density dependence of the nuclear symmetry energy, and the size of the neutron skin thickness in lead. In particular the constraints on "L", a parameter which measures the density dependence of the symmetry energy are strong: we find L to be relatively small.
These results are published in Phys. Rev. Lett. 108 (2012) 081102 .