Quantum Field Theory with Null-Fronted Metrics
arXiv:hep-th/9401160 · doi:10.1103/PhysRevD.50.7421
Abstract
There is a large class of classical null-fronted metrics in which a free scalar field has an infinite number of conservation laws. In particular, if the scalar field is quantized, the number of particles is conserved. However, with more general null-fronted metrics, field quantization cannot be interpreted in terms of particle creation and annihilation operators, and the physical meaning of the theory becomes obscure.
11 pages