Non-Perturbative Nekrasov Partition Function from String Theory

Understand

We calculate gauge instanton corrections to a class of higher derivative string effective couplings introduced in [1].

• We work in Type I string theory compactified on K3xT2 and realise gauge instantons in terms of D5-branes wrapping the internal space.
• In the field theory limit we reproduce the deformed ADHM action on a general {\Omega}-background from which one can compute the non-perturbative gauge theory partition function using localisation.
• This is a non-perturbative extension of [1] and provides further evidence for our proposal of a string theory realisation of the {\Omega}-background.