Where does energy come from in QFT?

[lindl]

Homework Statement

The origin of energy in the creation of elementary particles

Relevant Equations

QFT

When we say energy is applied to that field to create an excitation which is a particle, where does that energy come from and how is it applied? For example on beta decay where a new electron is formed, where does the energy come from the create an excitement in the electron field?

 

[Gaussian97]

From the W boson that it's annihilated.