Quantum Field Theory/Quantization of free fields

< Quantum Field Theory


Spin 0 fieldEdit

Real and complex scalar fields. Klein-Gordon equation. Plane-wave (normal mode) solutions. Generation and anihilation operators. Hamiltonian. Commutation relations.Edit

Real and complex scalar fields.Edit

The equations of motion for a real scalar field   can be obtained from the following lagrangian densities


and the result is  .

The complex scalar field   can be considered as a sum of two scalar fields:   and  ,  

The Langrangian density of a complex scalar field is


Klein-Gordon equationEdit

Klein-Gordon equation is precisely the equation of motion for the spin-0 particle as derived above:  

Spin 1/2 fieldEdit

Dirac equationEdit

The Dirac equation is given by:


where   is a four-dimensional Dirac spinor. The   matrices obey the following anticommutation relation (known as the Dirac algebra):


Notice that the Dirac algebra does not define a priori how many dimensions the matrices should be. For a four-dimensional Minkowski space, however, it turns out that the matrices have to be at least  .

Plane-wave (normal mode) solutions. Generation and anihilation operators. Hamiltonian. Anticommutation relations.Edit

Spin 1 fieldEdit

Massive spin 1 field. Additional (Lorentz) condition to eliminate spin-0.Edit

Massless spin 1 field. Gauge invariance. Quantization within Coulomb (radiation) gauge.Edit

Spin-statistics theorem. Discrete symmetries (C,P,T). CPT theorem.Edit