11/10/2019Burkhard EdenPolylogarithms from the Bound State S-matrix 
04/11/2019 Alexei Rosly Conformal properties of the Self-  Dual YM Theory I would like to promote the Self-Dual Yang Mills Theory as a possibly simplest non-linear conformal field theory in 4d with no supersymmetry. This field theory possesses UV divergences, but these do not spoil the conformal covariance: the effect of renormalization is that the coupling constant does not run, it is only a field renormalization which is needed. This results in a conformal invariance of the effective action under anomalous conformal transformations. I can give only a partial, but hopefully convincing proof of the latter. If the time permits I will also discuss the issue of conformal observables in this theory in relation with twistor geometry.
 30/01/2020 Riccardo Gonzo OPE at null infinity We will provide a new subleading collinear expansion of flat space amplitudes in the Mellin basis, which will make contact with the OPE of the dual theory at null infinity. Assuming the existence of highest-weight representation for the OPE, we will derive a recursion relation for the coefficients of the subleading collinear expansion based on the extended BMS algebra which includes also singular supertranslations. The outcome is that not only the leading OPE coefficient is determined by the asymptotic symmetries at null infinity but also the subleading coefficients at first order in the holomorphic and antiholomorphic expansion. Various examples of amplitudes of massless particles will be discussed.
 27/2/2020   Leonardo de la Cruz Feynman integrals as A-hypergeometric functions 
 12/3/2020 Rene Pascal Klausen Hypergeometric series representations of Feynman integrals 
 2/4/2020 Mikhail Shifman TBA