Analytic nonperturbative solutions for closed string field theory far from the starting background

Construct analytic, nonperturbative solutions to the closed string field theory equations of motion that represent backgrounds finitely displaced (i.e., not related by small marginal deformations) from the initial conformal field theory, thereby providing analogues of the Erler–Maccaferri solutions known for open string field theory.

Background

The paper contrasts the open-string case, where Erler–Maccaferri constructed explicit nonperturbative solutions mapping between different open-string backgrounds, with the closed-string case, where only infinitesimal background shifts are presently controlled via background-independence arguments.

For closed string field theory, existing results establish equivalences only for backgrounds connected by small marginal deformations; extending this to finite (‘far away’) background changes would require analytic solutions to the closed string field theory equations of motion, which are currently unavailable.