Are Noether charges a rep of the generators on the Hilbert space

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SUMMARY

The discussion centers on the relationship between conserved charges derived from Noether's theorem and their representation as generators on the Hilbert space. Specifically, the conserved charges, denoted as Q^a, are defined by the integral Q^a = ∫ d^3x (∂L/∂∂₀φᵢ) Δφᵢᵃ. It is established that operators transform according to the relation &hat;O → e^{i t_a Q^a} &hat;O e^{-i t_a Q^a}, confirming that these charges indeed represent the generators on the Hilbert space. Notably, in the context of internal symmetries, the charges do not need to be conserved to fulfill this role.

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  • Noether's theorem
  • Hilbert space representation theory
  • Lie algebra of symmetry groups
  • Quantum field theory basics
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a2009
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I'm trying to understand the relationship between conserved charges and how operators transform. I know that we can find conserved charges from Noether's theorem. If (for internal symmetries) I call them Q^a = \int d^3x \frac{\partial L}{\partial \partial_0 \phi_i} \Delta \phi_i^a then is it always the case that operators transform like

\hat O \rightarrow e^{i t_a Q^a} \hat O e^{-i t_a Q^a}

i.e. are the conserved charges the rep of the generators on the Hilbert space?


Thanks for any help!
 
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Yes, they do generate the correct transformation on the fields AND satisfy the Lie algebra of the symmetry group. More importantly, they ( in the internal case) DON’T need to be CONSERVED to do the job.

sam
 

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