Superstring at the boundary of open supermembrane interacting with D=4 supergravity and matter supermultiplets.

We present the complete supersymmetric and κ-symmetric action for the 4- dimensional interacting system of open supermembrane, dynamical supergravity and 3-form matter multiplets. The cases of a single 3-form matter multiplet and a quite generic model with a number of nonlinear interacting double 3-form multiplets are considered. In all cases the fermionic parameter of the κ-symmetry is subject to two apparently different projection conditions which suggests that the ground state of the system, in particular a domain junction, might preserve at most 1/4 of the spacetime supersymmetry. The boundary term of the open supermembrane action, needed to preserve the κ-symmetry, has the meaning of the action of a superstring. The Wess-Zumino term of this superstring action is expressed in terms of real linear superfield playing the role of Stückelberg field for the 3-form gauge symmetry. This indicates that this symmetry is broken spontaneously by the superstring at the boundary of supermembrane. [ABSTRACT FROM AUTHOR]