Quantum Field Theory In Curved Spacetime: Quant... -

: In the early, rapidly expanding universe, time-varying gravitational fields can "excite" the vacuum, creating elementary particles that seed the large-scale structure of the universe. Robert Wald - Quantum Field Theory in Curved Spacetime

: A second observer might decompose the same field using a different basis and operators Mixing : The new annihilation operator Quantum Field Theory in Curved Spacetime: Quant...

) will contain a non-zero number of particles according to the second observer. 3. Key Phenomena : In the early, rapidly expanding universe, time-varying