ar X iv : h ep - t h / 06 03 12 5 v 1 1 5 M ar 2 00 6 hep - th / 0603125 ITP – UH – 05 / 06 Noncommutative Instantons on C

ar X iv : h ep - t h / 05 02 11 7 v 1 1 3 Fe b 20 05 hep - th / 0502117 ITP – UH – 02 / 05 Noncommutative Instantons in 4 k Dimensions

We consider Ward’s generalized self-duality equations for U(2r) Yang-Mills theory on R and their Moyal deformation under self-dual noncommutativity. Employing an extended ADHM construction we find two kinds of explicit solutions, which generalize the ’t Hooft and BPST instantons from R to noncommutative R. The BPST-type configurations appear to be new even in the commutative case.

ar X iv : h ep - t h / 06 05 27 4 v 2 1 6 A ug 2 00 6 hep - th / 0605274 Metric and coupling reversal in string theory

Invariance under reversing the sign of the metric G M N (x) and/or the sign of the string coupling field H Universe K contains only F1 and NS5 of IIB and Heterotic SO(32).

ar X iv : h ep - t h / 06 05 27 4 v 1 2 8 M ay 2 00 6 hep - th / 0605274 Metric and coupling reversal in string theory

Invariance under reversing the sign of the metric G M N (x) and/or the sign of the string coupling field H Universe K contains only F1 and NS5 of IIB and Heterotic SO(32).

ar X iv : h ep - t h / 06 05 27 5 v 1 2 9 M ay 2 00 6 Second Order Noncommutative Corrections to Gravity

In this work, we calculate the leading order corrections to general relativity formulated on a canonical noncommutative spacetime. These corrections appear in the second order of the expansion in theta. First order corrections can only appear in the gravity-matter interactions. Some implications are briefly discussed. [email protected] [email protected]

ar X iv : h ep - t h / 06 12 12 8 v 1 1 3 D ec 2 00 6 Riemannian Geometry of Noncommutative Surfaces