Binding of holes in the Hubbard model

We present a new numerical method for the study of binding energies of particles in fermionic systems. Working with an imaginary chemical potential we can obtain results in the canonical ensemble by simple modifications of standard numerical techniques. We applied the technique to the two-dimensional Hubbard model observing binding of holes at half-filling on lattices of 4×4 sites. For U/t=4 we estimate that the binding energy is =-0.10 0.02.