Quantum field theory (QFT) is the theoretical framework unifying classical field theory, special relativity, and quantum mechanics, in which fundamental entities are not localized particles but quantum fields that permeate spacetime, with particles reinterpreted as discrete excitations (quanta) of these underlying fields. Two principal formal approaches exist for constructing and quantizing a field theory: canonical quantization, which promotes classical fields and their conjugate momenta to operators obeying commutation relations and introduces creation/annihilation operators, and the path-integral (sum-over-histories) formulation, which computes probability amplitudes by summing complex phase-weighted contributions over all possible particle trajectories. This body of theory sits within theoretical/mathematical physics, extending non-relativistic quantum mechanics to a relativistically consistent, field-based description in which particle number is not fixed.
Quantum field theory (QFT) is the theoretical framework unifying classical field theory, special relativity, and quantum mechanics, in which fundamental entities are not localized particles but quant…