STRING THEORY EFFECTIVE ACTION: STRING LOOP CORRECTIONS
Arkady A. Tseytlin · International Journal of Modern Physics A · 1988
We discuss the general ideology of the computation of string loop corrections to the effective action for the massless modes of the string. Both the S-matrix and the sigma-model approaches are presented. It is emphasized that the effective action is a more general and better defined object than the S-matrix. In particular, it is finite in spite of modular infinities that may be present in loop amplitudes computed near a “wrong” vacuum. The case of the disc topology in the open-closed string theory is treated in some detail. Some issues concerning the soft dilaton vertex operators related to the infinities of the string amplitudes are disucssed.