SUPERSYMMETRY AND DIMENSIONALITY IN THE SUPERSTRING THEORY

Abstract

The realization of non-linear global supersymmetry in the superstring theory requires the quadratic fermionic Lagrangian [Formula: see text], defined from the D-dimensional, Minkowski-space energy–momentum tensor Tmn, to have the same form as the quadratic gravitational contribution [Formula: see text] to the superstring Lagrangian. Here, we prove that this condition is only satisfied for the heterotic string theory after reduction to D = 4, irrespective of whether the original source of [Formula: see text] in ten or twenty-six dimensions is the quadratic term [Formula: see text] or the quartic term [Formula: see text]. If [Formula: see text] derives from [Formula: see text], the solution is D = 4 (or the unphysical value D = 1), while if we suppose that D≠4 and [Formula: see text] dominates, we obtain the (singular) solution (D-2)3 = 0. The world sheet is also discussed. The bosonic string and type-II superstring, on the other hand, yield solutions for D which are complex, non-integral, or at the singular point D = 2, where the Einstein equations hold identically.