# Feynman's vector potential, a physical meaning clue

• Abrain
In summary, the Feynman's vector potential definition for component m of the particle b at point x is given by integrating over the entire world line of the particle, using the invariant parameter b and the Dirac delta function. The 4-norm of x - b represents the boundary of the light cone of b, and the $\delta$ function is non-zero only if x is within this boundary.
Abrain
Hi everybody!

I'd like to understand the physical meaning of the Feynman's vector potential definition:

$$A_{m}^{(b)}(x) = e_b \int \delta (xb_{\mu}xb^{\mu})db_m(b), \qquad m=0,1,2,3$$

(component m of the vector potential of the particle b at the point x)

Here

- the integration is done over the whole world line of the b particle, parametrized by the invariant parameter b

- $$\delta$$ is the Dirac delta function

- $$xb_{\mu}xb^{\mu}$$ is the 4-norm of $$x - b$$

- So the $$\delta$$ function is non-zero $$\iff x$$ is in the boundary of the light cone of b.

Can you give me any clues?

Thanks!

...Up!

## What is Feynman's vector potential?

Feynman's vector potential is a mathematical concept used in electromagnetism to describe the behavior of electric and magnetic fields. It is a vector quantity that is related to the electric and magnetic potentials and is used to define the electromagnetic field.

## What is the physical meaning of Feynman's vector potential?

The physical meaning of Feynman's vector potential is that it represents the energy associated with the electric and magnetic fields. It is also related to the momentum of particles in the field and can help determine the behavior of charged particles in an electromagnetic field.

## How is Feynman's vector potential related to Maxwell's equations?

Feynman's vector potential is related to Maxwell's equations through the concept of gauge invariance. Gauge invariance states that the physical predictions of a system should not change when a certain mathematical transformation is applied. This transformation is known as a gauge transformation and it relates the vector potential to the electric and magnetic fields in Maxwell's equations.

## Can Feynman's vector potential be measured directly?

No, Feynman's vector potential cannot be measured directly. It is a mathematical concept that helps us understand the behavior of electric and magnetic fields. However, the effects of the vector potential can be measured indirectly through experiments and observations.

## What are some applications of Feynman's vector potential?

Feynman's vector potential has many applications in various fields such as electromagnetism, quantum mechanics, and particle physics. It is used to study the behavior of charged particles in electromagnetic fields, understand the properties of superconductors, and even in the development of new technologies such as magnetic levitation trains. It is also essential in the development of theories in quantum electrodynamics and the Standard Model of particle physics.

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