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Journal Club Matthias Wilhelm (Niels Bohr Institute Copenhagen)
room Zoom, instructions in abstract
In this talk, I discuss an operator product expansion for planar form factors of local operators in N=4 SYM theory. In this expansion, a form factor is decomposed into a sequence of known pentagon transitions and a new universal object - the form factor transition. This transition is subject to a set of non-trivial bootstrap constraints, which can be used to determine it at finite coupling. I demonstrate this for MHV form factors of the chiral half of the stress tensor supermultiplet, which in particular contains the chiral Lagrangian and the 20'. ---- Part of London Integrability Journal Club. If you are a new participant, please register filling the form at integrability-london.weebly.com. The link will be emailed.
Regular Seminar Matthias Wilhelm (Humboldt)
room G.O. Jones 610
We study the form factor of a generic gauge-invariant local composite operator in N=4 SYM theory. At tree-level and for a minimal number of external fields, the form factor exactly realises the spin-chain picture of N=4 SYM theory in the language of scattering amplitudes. Via generalised unitarity, we obtain the cut-constructible part of the one-loop correction to the minimal form factor of a generic operator. Its UV divergence yields the complete one-loop dilatation operator of the theory. We also compute the complete two-loop correction to the two-point form factor of the Konishi operator via unitarity and obtain the two-loop Konishi anomalous dimensions from it. For the Konishi operator as well as other non-protected operators, important subtleties arise which require an extension of the method of unitarity. Moreover, since the inclusion of non-protected operators into the action renders it formally non-supersymmetric, the form factors of these operators share many features with quantities in QCD, such as the occurrence of rational terms. The talk is based on the recent works 1410.6309 and 1410.8485.