Symmetries of the stationary Einstein--Maxwell--dilaton theory

Abstract

Gravity coupled three--dimensional $σ$--model describing the stationary Einstein--Maxwell--dilaton system with general dilaton coupling is studied. Killing equations for the corresponding five--dimensional target space are integrated. It is shown that for general coupling constant $α$ the symmetry algebra is isomorphic to the maximal solvable subalgebra of $sl(3,R)$. For two critical values $α=0$ and $α=\sqrt{3}$, Killing algebra enlarges to the full $sl(3,R)$ and $su(2,1)\times R$ algebras respectively, which correspond to five--dimensional Kaluza--Klein and four--dimensional Brans--Dicke--Maxwell theories. These two models are analyzed in terms of the unique real variables. Relation to the description in terms of complex Ernst potentials is discussed. Non--trivial discrete maps between different subspaces of the target space are found and used to generate new arbitrary--$α$ solutions to dilaton gravity.