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formulas:canonical_commutation_relations [2018/05/03 13:41] jakobadmin [Abstract] |
formulas:canonical_commutation_relations [2018/05/05 12:22] 138.186.136.73 ↷ Links adapted because of a move operation |
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\begin{equation} \label{qftcomm} [\Phi(x), \pi(y)]=\Phi(x) \pi(y) - \pi(y) \Phi(x) = i \delta(x-y) \end{equation} where $\delta(x-y)$ is the Dirac delta distribution and $\pi(y) = \frac{\partial \mathscr{L}}{\partial(\partial_0\Phi)}$ is the conjugate momentum. | \begin{equation} \label{qftcomm} [\Phi(x), \pi(y)]=\Phi(x) \pi(y) - \pi(y) \Phi(x) = i \delta(x-y) \end{equation} where $\delta(x-y)$ is the Dirac delta distribution and $\pi(y) = \frac{\partial \mathscr{L}}{\partial(\partial_0\Phi)}$ is the conjugate momentum. | ||
- | It tells us that the fields in [[theories:quantum_field_theory|quantum field theory]] $\Phi(x)$ can‘t be simply a function, but must be __operators__. In contrast, ordinary functions and numbers commute: | + | It tells us that the fields in [[theories:quantum_field_theory:canonical|quantum field theory]] $\Phi(x)$ can‘t be simply a function, but must be __operators__. In contrast, ordinary functions and numbers commute: |
For example $f(x)=3x$ and $g(y)= 7y^2 +3$ clearly commute $$ [f(x) , g(x)]= f(x)g(x) - g(x) f(x) = 3x (7y^2 +3) -(7y^2 +3) 3x =0. $$ | For example $f(x)=3x$ and $g(y)= 7y^2 +3$ clearly commute $$ [f(x) , g(x)]= f(x)g(x) - g(x) f(x) = 3x (7y^2 +3) -(7y^2 +3) 3x =0. $$ | ||
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The problem of finding an appropriate mathematical interpretation of the canonical commutation | The problem of finding an appropriate mathematical interpretation of the canonical commutation | ||
relations is the subject of [[advanced_tools:quantization|quantization theory]]. | relations is the subject of [[advanced_tools:quantization|quantization theory]]. | ||
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+ | * A good discussion can be found [[https://mathoverflow.net/questions/55988/quantum-mechanics-formalism-and-c-algebras/56003|here]]. | ||
<tabbox Why is it interesting?> | <tabbox Why is it interesting?> | ||