QUANTUM CLOSED STRINGS FROM MINIMAL AREA
Barton Zwiebach · Modern Physics Letters A · 1990
Canonical and factorizable off-shell amplitudes for covariant closed string theory can be obtained from string diagrams of minimal area. Evidence is given that all higher genus minimal area string diagrams can be built using vertices and propagators, implying that the off-shell amplitudes arise from the Feynman rules of a full quantum theory of closed strings. The quantum action gives an exact solution of the full master equation of Batalin and Vilkoviski.