19.11.2014 (Wednesday)

Form factors, Anomalous Dimensions and the Dilatation Operator of N=4 SYM Theory

Regular Seminar Matthias Wilhelm (Humboldt)

at:
16:00 QMW
room G.O. Jones 610
abstract:

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.