## What is conserved in Feynman diagram?

The simple answer is – everything! If there’s a symmetry in your theory then the associated Noether charge must be conserved at a Feynman vertex.

## What is a propagator QFT?

In quantum mechanics and quantum field theory, the propagator is a function that specifies the probability amplitude for a particle to travel from one place to another in a given period of time, or to travel with a certain energy and momentum.

What is exchange particle in Feynman diagram?

The photon is the exchange particle responsible for the electromagnetic force. The force between two electrons can be visualized in terms of a Feynman diagram as shown below. The infinite range of the electromagnetic force is owed to the zero rest mass of the photon.

### How do you find the exchange particle in Feynman diagram?

In a Feynman diagram, an exchange particle is a line (wavy, solid, dashed or curled), which does not have a “free” end, meaning that it is connected to at least two other lines at both ends. You should not think about them as particles though.

### Why does the Klein-Gordon equation fail?

Any solution of the free Dirac equation is, for each of its four components, a solution of the free Klein–Gordon equation. The Klein–Gordon equation does not form the basis of a consistent quantum relativistic one-particle theory. There is no known such theory for particles of any spin.

Is there an anti gluon?

The set of all gluons contains the antiparticles of each member of itself. But while there is only one photon which is own antiparticle (it is a singlet), each specific gluon has an antiparticle distinct of itself. But its antiparticle is just another gluon and does not deserve to be called an “antigluon”.

## Why do we need Klein-Gordon’s equation?

The equation describes all spinless particles with positive, negative, and zero charge. Any solution of the free Dirac equation is, for each of its four components, a solution of the free Klein–Gordon equation. The Klein–Gordon equation does not form the basis of a consistent quantum relativistic one-particle theory.