Scherk-Schwarz mechanism

In theoretical physics, the Scherk-Schwarz mechanism for a field φ basically means that φ is a section of a non-trivializable fiber bundle (not necessarily a vector bundle since φ needn't be linear) which is fixed by the model. This is called a "twist" by physicists.

Note that this can never occur in a spacetime which is homeomorphic to Rⁿ, which is a contractible space. However, for Kaluza-Klein theories, the Scherk-Schwarz mechanism is a possibility which can't be neglected.