HET- seminar: Johannes Broedel

Speaker:  Johannes Broedel

Title: Amplitude recursions with an extra marked point

Abstract: Scattering amplitudes of multiplicity N can be obtained from those at multiplicity N+1 by taking soft and collinear limits. Using a construction on Riemann surfaces with marked points, one can reverse this operation and obtain higher-point scattering amplitudes from those at lower multiplicity. Even more, one can obtain N-point one-loop open-string amplitudes from (N+2)-point open-string tree-level amplitudes, thus bridging between different genera. I will introduce the objects (iterated (Selberg-) integrals) and differential equations (KZ and KZB-type) leading to a purely algebraic and properly regularized representation of the stringy scattering amplitudes mentioned above. I will comment on general applicability of the structure - which might qualify as a starting point for a S-matrix theory.