Soliton Fay identities. I. Dark soliton case

Abstract: We derive a set of bilinear identities for the determinants of the matrices that have been used to construct the dark soliton solutions for various models. To give examples of the application of the obtained identities we present soliton solutions for the equations describing multidimensional quadrilateral lattices, Darboux equations and multidimensional multicomponent systems of the nonlinear Schrodinger type.