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Unlike the conservation laws for energy, momentum, angular momentum and electric charge, the conservations of L and B are not rigorously covered in textbooks. So my questions

- How can I tell from a Lagrangian that it conserves L, B, B-L or so?

- Is there a Noether mechanism leading to these conservations? What are the associated symmetries?

- In QED, from the Feynman diagrams of second quantization it is quite obvious that the electron number is conserved; but this structure emerges from the charge conservation, doesn’t it?

- Electric charge is associated with the phase of the wave function of a particle, and from first quantization one can well see how this works; but the particle number should be associated with the norm of the wave function in first quantization; how can one comprehend that it is conserved?

Thank you very much in advance!