Jib condition
Fock states (named after the physicist Vladimir Alexandrowitsch Fock ) are states of a certain number of particles in Fock space in quantum mechanical many-particle theory and quantum field theory , which can serve as a basis there .
In general, a distinction is made between particles
They differ essentially in the commutation relations of the operators representing them, their quantum statistics :
- According to the Fermi-Dirac statistics, fermions (like the electron ) can not occupy a state with the same quantum numbers (including their spin alignment) in Fock space or only once
- in the case of bosons (such as photons or phonons ), according to the Bose-Einstein statistics, there is no limit to the number of particles in a certain state.
States in Fock space are built up with the help of creation and annihilation operators . One also speaks of occupation number representation or second quantization .
In Fock space, states can also be constructed in which the number of particles is only given in the mean and can fluctuate around the mean value , for example coherent states in laser physics .