Half-maximal Extended Drinfel'd Algebras

Extended Drinfel'd algebra (ExDA) is the underlying symmetry of non-Abelian duality in the low-energy effective theory of string theory. Non-Abelian U-dualities in maximal supergravities have been studied well, but there has been no study on non-Abelian dualities in half-maximal supergravities. In this paper, we construct the ExDA for half-maximal supergravities in $d\geq 4$. We also find an extension of the homogeneous classical Yang-Baxter equation in these theories.