Universality in string interactions

Abstract

In this note, we provide evidence for universality in the low-energy expansion of tree-level string interactions. More precisely, in the α ′ -expansion of tree-level scattering amplitudes, we conjecture that the leading transcendental coefficient at each order in α ′ is universal for all perturbative string theories. We have checked this universality up to seven points and trace its origin to the ability to restructure the disk integrals of open bosonic string into those of the superstring. The accompanying kinematic functions have the same low-energy limit and do not introduce any transcendental numbers in their α ′ -corrections. Universality in the closed-string sector then follows from KLT-relations.

Gravitational couplings on D-brane revisited

“…Therefore we need to compute the expansion of S-matrix amplitude of two gravitons from D p -branes at this order which includes t-channel, s-channel and contact terms (3.3)-(3.5). This calculation also support the conjecture of uniform transcendentality in string theories in [18]. The details of field theory computations are presented in subsection 3.2.…”

“…This feature has been studied recently in [18] that α expansion of Bosonic string amplitudes has the same transcendental pieces as found for the Superstring. Our calculations also support their conjecture of uniform transcendentality in string theories.…”

“…This has been studied at different orders of α , for example see [11][12][13][14][15][16][17][18][19] where we have used in this paper. In computing the effective gravitational actions on D p -branes one expects that the above mentioned field redefinition is important at each order of α expansion.…”

Factorization of chiral string amplitudes

“…In [24] it was conjectured, and explicitly verified up to seven-points, that the massless bosonic open string amplitudes A bos admits a similar expansion as that for A super…”

Abelian Z-theory: NLSM amplitudes and α ′ -corrections from the open string

“…Massless n-point amplitudes of the open superstring [8] and conjecturally those of the open bosonic string [94] possess cyclic integrands of the following form:…”