Comments on Chern-Simons Contact Terms in Three Dimensions

Understand

We study contact terms of conserved currents and the energy-momentum tensor in three-dimensional quantum field theory.

• They are associated with Chern-Simons terms for background fields.
• While the integer parts of these contact terms are ambiguous, their fractional parts are meaningful physical observables.
• In N=2 supersymmetric theories with a U(1)_R symmetry some of these observables lead to an anomaly.