equations:klein-gordon_equation

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equations:klein-gordon_equation [2018/04/16 09:12] jakobadmin [Intuitive] |
equations:klein-gordon_equation [2021/03/31 18:22] (current) edi [Concrete] |
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* A nice discussion can be found in [[http://www.quantumfieldtheory.info/website_Chap03.pdf |chapter 3 of Klauber's Student Friendly QFT book]] | * A nice discussion can be found in [[http://www.quantumfieldtheory.info/website_Chap03.pdf |chapter 3 of Klauber's Student Friendly QFT book]] | ||

* For an elementary derivation of the Klein-Gordon equation see Physics from Symmetry by Schwichtenberg | * For an elementary derivation of the Klein-Gordon equation see Physics from Symmetry by Schwichtenberg | ||

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+ | ---- | ||

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+ | **Graphical Summary** | ||

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+ | The diagram below shows the Klein-Gordon equation and its Lagrangian in various forms. For a more detailed explanation see [[https://esackinger.wordpress.com/|Fun with Symmetry]]. | ||

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+ | {{:equations:klein_gordon.jpg?nolink}} | ||

<tabbox Abstract> | <tabbox Abstract> | ||

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<tabbox Why is it interesting?> | <tabbox Why is it interesting?> | ||

- | The Klein-Gordon equation is the correct equation of motion that describes free [[basic_notions:spin|spin]] $1$ particles. | + | The Klein-Gordon equation is the correct equation of motion that describes free [[basic_notions:spin|spin]] $0$ particles. For a spin-1 generalization see the Duffin-Kemmer-Petiau equation. |

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* $\partial _{\mu} $ denotes the partial derivative and $\partial _{\mu} \partial ^{\mu}$ stands for a sum using the Einstein sum convention, i.e. $\partial _{\mu} \partial ^{\mu} = \partial _0 \partial^0 - \partial _1 \partial^1 -\partial _2 \partial^2 -\partial _3 \partial^3$, | * $\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, | * $m$ 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. | + | * $\Phi$ describes the spin $0$ field if we work in a field theory. |

+ | * Note: $\Phi$ cannot be interpreted as a wavefunction because it is a real valued field; it is its own anti-particle like the Majorana fermion. Only in the case that it is the U(1)-charged (requires 2 independent real Klein Gordon fields that are symmetry transform into each other) is a naive wavefunction interpretation possible. Basically, you get a relativistic scalar superfluid field. Nevertheless, there are single particle wavefunctions lurking in the single real Klein-Gordon theory. But you need to use the coherent state representation to see the 1st quantized operators from the complex annihilation and creation operators. Essentially undoing the second quantization. | ||

equations/klein-gordon_equation.1523862738.txt.gz · Last modified: 2018/04/16 07:12 (external edit)

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