The effective action for the 4-point functions in abelian open superstring theory

We construct the derivative corrections to the four-point vertices in the abelian open string effective action to all orders in alpha'. The result is based on the structure of the string four-point function. Supersymmnetry of these vertices is guaranteed by the supersymmetry of the F^4 term in the effective action. By this construction we establish the existence of an infinite number of supersymmetry invariants, the number of invariants at order alpha'^n grows linearly with n.Comment: 11 pages, 1 figure, v2: additional remarks in Section 5, added references, v3: additional remarks in Section 4 and minor correction

Derivative corrections in 10-dimensional super-Maxwell theory

We construct the supersymmetric effective action at order alpha'(4) of the abelian open superstring. It includes the alpha'4 terms in the abelian Born-Infeld action, and in particular the leading derivative correction of the form partial derivative(4)F(4). Besides linear supersymmetry this sector of the open string effective action also has a nonlinear supersymmetry. The terms partial derivative(4)F(4) and their fermionic partners have an arbitrary coefficient, and we discuss the possible fate of such coefficients when higher orders in alpha' are included