Gravitational instantons from closed superstring field theory

A bstract We test exact marginality of the deformation describing the resolution of a ℤ 2 orbifold by analyzing the closed superstring equations of motion to third order in the size, including α ′ corrections. We find that the third order correction is unobstructed for all deformation moduli. We are also able to reproduce the Eguchi-Hanson gravitational instanton up to the second order in the field theory limit with a suitable choice of moduli.