Variant vector-tensor multiplets in supergravity: classification and component reduction

The recent paper arXiv:1205.6881 has developed superform formulations for two versions of the vector-tensor multiplet and their Chern-Simons couplings in four-dimensional N = 2 conformal supergravity. One of them is the standard vector-tensor multiplet with the central charge gauged by a vector multiplet. The other is the variant vector-tensor multiplet with the property that its own one-form gauges the central charge. Here a more general setup is presented in which the known versions reside as special cases. Analysis of the setup demonstrates that under certain assumptions there are two distinct variants, corresponding to the two formulations in arXiv:1205.6881. This provides a classification scheme for vector-tensor multiplets. We then show that our superspace description leads to an efficient means of deriving component actions in supergravity. The entire action including all fermionic terms is derived for the non-linear vector-tensor multiplet. This extends the results of de Wit et al. in hep-th/9710212, where only the bosonic sector appeared. Finally, the bosonic sector of the action for the variant vector-tensor multiplet is given.