Noncommutative quantum gravity

The possible role of gravity in a noncommutative geometry is investigated. Due to the Moyal *-product of fields in noncommutative geometry, it is necessary to complexify the metric tensor of gravity. We first consider the possibility of a complex Hermitian, nonsymmetric g(mu nu), and discuss the problems associated with such a theory. We then introduce a complex symmetric (non-Hermitian) metric, with the associated complex connection and curvature, as the basis of a noncommutative spacetime geometry. The spacetime coordinates are in general complex and the group of local gauge transformations is associated with the complex group of Lorentz transformations CSO(3, 1). A real action is chosen to obtain a consistent set of held equations. A Weyl quantization of the metric associated with the algebra of noncommuting coordinates is employed. (C) 2000 Published by Elsevier Science B.V.