Quantum Field Theory In Curved Spacetime: Quant... May 2026

: The concept of a "particle" becomes local and observer-dependent. Different observers (e.g., one inertial and one accelerating) may disagree on whether a state contains particles or is a vacuum.

bj=∑i(αjiai+βji*ai†)b sub j equals sum over i of open paren alpha sub j i end-sub a sub i plus beta sub j i end-sub raised to the * power a sub i raised to the † power close paren If the "mixing coefficient" βjibeta sub j i end-sub is non-zero, the vacuum of the first observer ( Quantum Field Theory in Curved Spacetime: Quant...

Quantum Field Theory in Curved Spacetime: Quantized Fields and Semiclassical Gravity : The concept of a "particle" becomes local