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equations:klein-gordon_equation

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# Klein-Gordon Equation

$$( \partial _{\mu} \partial ^{\mu}+m^2)\Phi = 0$$
Definitions
• $\partial _{\mu}$ denotes the partial derivative and $\partial _{\mu} \partial ^{\mu}$ stands for a sum using the Einstein sum convention, i.e. $\partial _{\mu} \partial ^{\mu} = \partial _0 \partial^0 - \partial _1 \partial^1 -\partial _2 \partial^2 -\partial _3 \partial^3$.
• $m$ denotes the mass of the particle.
• $\Phi$ is either the wave function of the spin $0$ particle if we use the Klein-Gordon equation in a particle theory, or describes the spin $0$ field if we work in a field theory.

## Why is it interesting?

The Klein-Gordon equation is the correct equation of motion that describes free spin $1$ particles.

## Layman

Explanations in this section should contain no formulas, but instead colloquial things like you would hear them during a coffee break or at a cocktail party.

## Researcher

The motto in this section is: the higher the level of abstraction, the better.
Common Question 1
Common Question 2

Example1
Example2: