On tree-level higher order gravitational couplings in superstring theory

الأصل · EN

We consider the scattering amplitudes of five and six gravitons at tree-level in superstring theory. Their power series expansions in the Regge slope alpha' are analyzed through the order alpha'⁸ showing some interesting constraints on higher order gravitational couplings in the effective superstring action like the absence of R⁵ terms. Furthermore, some transcendentality constraints on the coefficients of the non-vanishing couplings are observed: the absence of zeta values of even weight through the order alpha'⁸ like the absence of zeta(2) zeta(3) R⁶ terms. Our analysis is valid for any superstring background in any space-time dimension, which allows for a conformal field theory description.