The contact of the Fermi gas at unitarity*

The unitary Fermi gas is a strongly correlated system with a short-range interaction that saturates the upper bound on the modulus of the two-particle s-wave scattering amplitude. It is characterized by an infinite scattering length and sits in the middle of the BCS-BEC crossover. The contact of this system is a quantity that describes short-range pairing correlations and appears in the high momentum tail of the momentum distribution and the static structure factor, as well as in the high-frequency tail of the shear viscosity spectral function. There have been a number of recent calculations and important experimental advances towards determining the contact for the unitary Fermi gas. We present results for the temperature dependence of the contact at unitarity using finite-temperature auxiliary-field quantum Monte Carlo (AFMC) methods on the lattice. Our calculations are carried out within the canonical ensemble with multiple filling factors and extrapolated to the continuum limit. We compare our results with other theoretical calculations and with experiment.