## 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.