The Lattice Schrodinger Functional and the Background Field Effective   Action
  We propose a new method that by using the lattice Schr\"odinger functional allows to investigate the effective action for external background fields in lattice gauge theories. We show that this method gives sensible results for the case of four-dimensional U(1) gauge theory in an external constant magnetic field. 
P. Cea, L. Cosmai, and A. D. Polosa