Nambu–Goto action

Summary

The Nambu–Goto action is the classical action of a relativistic string. Up to sign, it is the tension of the string times the area of the surface it sweeps out in spacetime. It was proposed independently by Yoichiro Nambu and Tetsuo Goto around 1970. Its extremals are the surfaces of zero mean curvature in spacetime, the analogue for strings of geodesics for point particles. Because of the square root in the area, it is hard to quantize directly, and one usually replaces it by the classically equivalent Polyakov action.