EUCLIDEAN-SIGNATURE SUPERGRAVITIES, DUALITIES AND INSTANTONS

We study the Euclidean-signature supergravities that arise by compacti fying D = 11 supergravity or type IIB supergravity on a torus that inc ludes the time direction. We show chat the usual T-duality relation be tween type ZIA and type IIB supergravities compactified on a spatial c ircle no longer holds if the reduction is performed on the time direct ion. Thus there are two inequivalent Euclidean-signature nine-dimensio nal maximal supergravities. They become equivalent upon further spatia l compactification to D = 8. We also show that duality symmetries of E uclidean-signature supergravities allow the harmonic functions of any single-charge or multicharge instanton to be rescaled and shifted by c onstant factors. Combined with the usual diagonal dimensional reductio n and oxidation procedures, this allows us to use the duality symmetri es to map any single-charge or multi-charge p-brane soliton, or any in tersection, into its near-horizon regime. Similar transformations can also be made on non-extremal p-branes. We also study the structures of duality multiplets of instanton and (D - 3)-brane solutions. (C) 1998 Published by Elsevier Science B.V.