Green functions and twist correlators for N branes at angles Original Research Article

We compute the Green functions and correlator functions for N twist fields for branes at angles on image and we show that there are image different configurations labeled by an integer M which is roughly associated with the number of reflex angles of the configuration. In order to perform this computation we use an image invariant formulation and geometric constraints instead of Pochammer contours. In particular the image or image amplitude can be expressed without using transcendental functions. We determine the amplitudes normalization from image reduction without using the factorization into the untwisted sector. Both the amplitudes normalization and the OPE of two twist fields are unique (up to one constant) when the image symmetry is imposed. For consistency we find also an infinite number of relations among Lauricella hypergeometric functions.