Decoupling limits of sgoldstino modes in global and local supersymmetry

We study the decoupling limit of a superheavy sgoldstino field in spontaneously broken N=1 supergravity. Our approach is based on Kähler superspace, which, among others, allows direct formulation of N=1 supergravity in the Einstein frame and correct identifications of mass parameters. Allowing for a non-renormalizable Kähler potential in the hidden sector, the decoupling limit of a superheavy sgoldstino is identified with an infinite negative Kähler curvature. Constraints that lead to non-linear realizations of supersymmetry emerge as consequence of the equations of motion of the goldstino superfield when considering the decoupling limit. Finally, by employing superspace Bianchi identities, we identify the real chiral superfield, which will be the superconformal symmetry breaking chiral superfield that enters the conservation of the Ferrara-Zumino multiplet in the field theory limit of N=1 supergravity.