  The `dynamic' Hubbard Hamiltonian describes interacting fermions on a lattice
whose on-site repulsion is modulated by a coupling to a fluctuating bosonic
field. We investigate one such model, introduced by Hirsch, using the
determinant Quantum Monte Carlo method. Our key result is that the extended
s-wave pairing vertex, repulsive in the usual static Hubbard model, becomes
attractive as the coupling to the fluctuating Bose field increases. The sign
problem prevents us from exploring a low enough temperature to see if a
superconducting transition occurs. We also observe a stabilization of
antiferromagnetic correlations and the Mott gap near half-filling, and a near
linear behavior of the energy as a function of particle density which indicates
a tendency toward phase separation.
