Quantum Field Theory in Curved Spacetime: Quantized Fields and Semiclassical Gravity
. This approach serves as a robust approximation for environments where gravity is strong but quantum gravitational effects—such as fluctuations of the metric itself—are not yet dominant. 1. The Fundamental Shift: From Particles to Fields
Quantum Field Theory in Curved Spacetime (QFTCS) is a "hybrid" framework where matter fields are treated according to quantum principles, but the gravitational background is described classically by a fixed spacetime metric gμνg sub mu nu end-sub Quantum Field Theory in Curved Spacetime: Quant...
) will contain a non-zero number of particles according to the second observer. 3. Key Phenomena
: Strong gravitational fields near a black hole's event horizon polarize the vacuum, causing the black hole to emit thermal radiation and gradually lose mass. Quantum Field Theory in Curved Spacetime: Quantized Fields
To relate the perspectives of different observers or the state of fields at different times in an expanding universe, physicists use : Field Decomposition : A scalar field is expanded into a set of basis modes with creation and annihilation operators
: General curved backgrounds lack global Poincaré invariance and time-translation symmetry, making it impossible to define a unique, preferred vacuum state. The Fundamental Shift: From Particles to Fields Quantum
In flat (Minkowski) spacetime, Poincaré invariance provides a unique vacuum state and a global definition of "particles". In curved spacetime, these "crutches" disappear: