Nonperturbative tachyon potential from the Wilsonian renormalization group

The derivative expansion of the Wilsonian renormalization group generates additional terms in the effective β-functions not present in the perturbative approach. Applied to the nonlinear σ-model, to lowest order the vanishing of the β-function for the tachyon field generates an equation analogous to that found in open string field theory. Although the nonlinear term depends on the cutoff function, this arbitrariness can be removed by a rescaling of the tachyon field.