We report results of fully non-perturbative, Path Integral Monte Carlo (PIMC)
calculations for dilute neutron matter. The neutron-neutron interaction in the
s channel is parameterized by the scattering length and the effective range. We
calculate the energy and the chemical potential as a function of temperature at
the density \dens=0.003\fm^{-3}. The critical temperature \Tc for the
superfluid-normal phase transition is estimated from the finite size scaling of
the condensate fraction. At low temperatures we extract the spectral weight
function A(p,ω) from the imaginary time propagator using the methods of
maximum entropy and singular value decomposition. We determine the
quasiparticle spectrum, which can be accurately parameterized by three
parameters: an effective mass m∗, a mean-field potential U, and a gap
Δ. Large value of \Delta/\Tc indicates that the system is not a
BCS-type superfluid at low temperatures.Comment: 4 pages, 3 figure