Instantons from perturbation theory

Perturbation Theory with Instantons

The large k asymptotics (perturbation series) for integrals of the form ∫ F μe ikS , where μ is a smooth top form and S is a smooth function on a manifold F , both of which are invariant under the action of a symmetry group G, may be computed using the stationary phase approximation. This perturbation series can be expressed as the integral of a top form on the space M of critical points of S m...

Gravitational instantons from gauge theory.

A gauge theory can be formulated on a noncommutative (NC) spacetime. This NC gauge theory has anequivalent dual description through the so-called Seiberg-Witten (SW) map in terms of an ordinary gauge theory on a commutative spacetime. We show that all NC U(1) instantons of Nekrasov-Schwarz type are mapped to asymptotically locally Euclidean (ALE) gravitational instantons by the exact SW map and...

AdS3 Gravitational Instantons from Conformal Field Theory

A conformal field theory on the boundary of three-dimensional asymptotic anti-de Sitter spaces which appear as near horizon geometry of D-brane bound states is discussed. It is shown that partition functions of gravitational instantons appear as high and low temperature limits of the partition function of the conformal field theory. The result reproduces phase transition between the anti-de Sit...

Small Instantons in Matrix Theory

Small Instantons in String Theory

A long-standing puzzle about the heterotic string has been what happens when an instanton shrinks to zero size. It is argued here that the answer at the quantum level is that an extra SU(2) gauge symmetry appears that is supported in the core of the instanton. Thus in particular the quantum heterotic string has vacua with higher rank than is possible in conformal field theory. When k instantons...