What happens to conserved currents after spontaneos symmetry breaking?

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SUMMARY

In the context of spontaneous symmetry breaking, conserved currents remain conserved as they commute with the Hamiltonian, specifically the full charge operator Q, satisfying [H,Q] = 0. However, the axial current is not conserved due to the chiral anomaly, which alters the commutation relation to [H,QA] ≠ 0. The linear-σ model serves as a demonstration of this phenomenon, illustrating the distinction between chiral symmetry breaking and the implications of the chiral anomaly. For further understanding, resources such as Nambu's Nobel lecture and the Wikipedia page on chiral anomaly are recommended.

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  • Study the linear-σ model and its relevance to axial current conservation
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  • Review Nambu's Nobel lecture for deeper insights into symmetry breaking
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The discussion is beneficial for theoretical physicists, quantum field theorists, and students studying advanced concepts in particle physics, particularly those interested in symmetry breaking and anomalies.

alemsalem
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should the current still be conserved? since it stills commutes with the Hamiltonian and symmetry is just hidden.

but I just read that the linear-σ model was invented to demonstrate how the axial current could be partially conserved?

Thanks!
 
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the axial current is not conserved due to the chiral anomaly; that's different from chiral symmetry breaking, b/c for spontaneous symmetry breaking the full charge operator still commutes with the Hamiltonian H, i.e. [H,Q] = 0, whereas for an anomaly the (renormalized) operator doesn't, i.e. [H,QA] ≠ 0!

http://en.wikipedia.org/wiki/Chiral_anomaly
 
The Nobel lecture by Nambu is quite informative in this respect:
http://www.nobelprize.org/nobel_prizes/physics/laureates/2008/nambu_lecture.pdf
 

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