Three-dimensional Hypergravity Theories and Semigroup Expansion Method
In this work we present novel and known three-dimensional hypergravity theories which are obtained by applying the powerful semigroup expansion method. We show that the expansion procedure considered here yields a consistent way of coupling different three-dimensional Chern-Simons gravity theories with massless spin-$\frac{5}{2}$ gauge fields. First, by expanding the $\mathfrak{osp}\left(1|4\right)$ superalgebra with a particular semigroup a generalized hyper-Poincar\'e algebra is found. Interestingly, the hyper-Poincar\'e and hyper-Maxwell algebras appear as subalgebras of this generalized hypersymmetry algebra. Then, we show that the generalized hyper-Poincar\'e CS gravity action can be written as a sum of diverse hypergravity CS Lagrangians. We extend our study to a generalized hyper-AdS gravity theory by considering a different semigroup. Both generalized hyperalgebras are then found to be related through an In\"on\"u-Wigner contraction which can be seen as a generalization of the existing vanishing cosmological constant limit between the hyper-AdS and hyper-Poincar\'e gravity theories.