Non-extremal D-instantons

We construct the most general non-extremal deformation of the D-instantonsolution with maximal rotational symmetry. The general non-supersymmetricsolution carries electric charges of the SL(2,R) symmetry, which correspond toeach of the three conjugacy classes of SL(2,R). Our calculations naturallygeneralise to arbitrary dimensions and arbitrary dilaton couplings. We show that for specific values of the dilaton coupling parameter, thenon-extremal instanton solutions can be viewed as wormholes of non-extremalReissner-Nordstr\"om black holes in one higher dimension. We extend this resultby showing that for other values of the dilaton coupling parameter, thenon-extremal instanton solutions can be uplifted to non-extremal non-dilatonicp-branes in p+1 dimensions higher. Finally, we attempt to consider the solutions as instantons of (compactified)type IIB superstring theory. In particular, we derive an elegant formula forthe instanton action. We conjecture that the non-extremal D-instantons cancontribute to the R^8-terms in the type IIB string effective action.