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Six-dimensional origin of gravity mediated brane to brane supersymmetry breaking

Four dimensional supergravities may be the right framework to describe particle physics at low energies. Its connection to the underlying string theory can be implemented through higher dimensional supergravities which bear special characteristics. Their reduction to four dimensions breaks supersymmetry whose magnitude depends both on the compactifying manifold and the mechanism that generates the breaking. In particular compactifications, notably on a $S_1/Z_2$ orbifold, the breaking of supersymmetry occuring on a hidden brane, residing at one end of $S_1/Z_2$, is communicated to the visible brane which lies at the other end, via gravitational interactions propagating in the bulk. This scenario has been exemplified in the framework of the $N=2$, $D=5$ supergravity. In this note, motivated by the recent developments in the field, related to the six-dimensional description of the supergravity theory, we study the $N=2$, $D=5$ supergravity theory as originating from a $D=6$ supergravity which, in addition to the gravity, includes a number of tensor multiplets. This reduces to $N=1$, $D=4$ supergravity in a two step manner, first by Kaluza-Klein reduction followed by a $S_1/Z_2$ orbifold compactification. The resulting theory has striking similarities with the one that follows from the single standalone $N=2$, $D=5$ supergravity, with no reference to the underlying higher dimensional $D=6$ supergravity, and a structure that makes the supersymmetry breaking mechanisms studied in the past easily incorporated in higher dimensional schemes.