Past exam of the mathematics course of the University of Cambridge / 2024 / iii / Paper 306 / 4 / i / Solution

In Euclidean worldsheet signature, the string nonlinear sigma model action can be writtenThe factor of $i$ in the B-field term is absent in Lorentzian signature. Here $G$ is the target metric, $B$ the Kalb–Ramond field, and $\Phi$ the dilaton.