Supersizing axions with small size instantons

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...

Supersizing the Mind

Heating and small - size instantons in the O ( 3 ) σ model on the lattice

We study the role of small-size instantons in the determination of the topologi-cal susceptibility of the 2-d O(3) σ model on the lattice. In particular, we analyze how they affect the non-perturbative determination, by Monte Carlo techniques, of the renormalizations on the lattice. As a result, we obtain a high-precision non-perturbative determination of the mixing with the unity operator, fin...

Small Instantons and Weak Scale String Theory

We consider heterotic string compactifications to four dimensions when instantons shrink to zero size. If the standard model gauge group originates from the new gauge symmetry associated with the small instantons singularity, then the weakly or strongly coupled heterotic string scales can be taken to be arbitrarily low. The SO(32) and E8×E8 gauge groups can then be very weakly coupled even at t...