Static and rotating electrically charged black holes in three-dimensional Brans-Dicke gravity theories

We obtain static and rotating electrically charged black holes of a Einstein-Maxwell-dilaton theory of the Brans-Dicke type in 2+1 dimensions. The theory is specified by three fields, the dilaton phi the graviton g(mu nu) and the electromagnetic field F-mu nu, and two parameters, the cosmological constant Lambda and the Brans-Dicke parameter omega. It contains eight different cases, of which one distinguishes as special cases string theory, general relativity and a theory equivalent to four dimensional general relativity with one Killing vector. We find the Arnowitt-Derer-Misner mass, angular momentum, electric charge and dilaton charge and compute the Hawking temperature of the solutions. Causal structure and geodesic motion of null and timelike particles in the black hole geometries are studied in detail.