Symmetries + Conserved currents of SM

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Discussion Overview

The discussion centers on identifying and detailing the continuous symmetries of the Standard Model (SM) of particle physics, along with the associated conserved currents. Participants express a desire for specific information regarding gauge symmetries and chiral symmetries, particularly in the context of massless or Higgsless fields, and the complexities introduced by the Higgs mechanism.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant requests a comprehensive list of all continuous symmetries in the SM, specifically mentioning SU(1)xSU(2)xSU(3) gauge symmetries and chiral symmetries for fermions.
  • Another participant suggests looking at a paper, but the original poster expresses skepticism about its relevance, noting it focuses on global symmetries rather than local ones.
  • A later reply references Coleman Mandula's theorem, stating that the symmetries of the SM are a combination of spacetime and gauge symmetries, specifically Poincare and Yang-Mills gauge symmetries.
  • There is a discussion about the need for generators of the symmetries to derive conserved currents, with a mention of Noether's theorem as a method to find these currents.
  • One participant speculates on the nature of conserved currents related to Lorentz symmetry and chiral symmetries, suggesting that charge, color, and isospin may be involved.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the completeness of the list of continuous symmetries or the specifics of the associated conserved currents. Multiple viewpoints and uncertainties regarding the details of these symmetries and currents remain evident throughout the discussion.

Contextual Notes

Limitations include the lack of clarity on local versus global symmetries, the specific forms of conserved currents, and the complexities introduced by the Higgs mechanism. There is also uncertainty regarding the completeness of references provided.

michael879
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Can anyone give or point me to a list of ALL continuous symmetries in the standard model, and the conserved currents associated with them? I've spent a lot of time looking and for the most part everything I find is very abstract, where as I want the specific details to the SM (i.e. SU(N) gauge symmetries and chiral symmetries for massless/higgsless fields which are idealizations of the SM).

The continuous symmetries I am aware of are: SU(1)xSU(2)xSU(3) gauge symmetries and chiral symmetries for each fermion. As I haven't found an exhaustive list, I'm not sure if there are others.

I believe the conserved currents associated with these symmetries are RELATED to charge conservation and fermion number conservation. However, the higgs complicates the actual form of these currents and I don't know what they are.
 
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Bill_K said:
Hm, you could take a look at this paper.

Bill thank you, and I will check it out to confirm this, but I suspect its not what I'm looking for. I think I actually came across this paper in my search, but it does not include local symmetries.

"I present an overview of the standard model, concentrating on its global continuous symmetries, both exact and approximate"

The BEST reference I've found for the SM is: http://einstein-Schrödinger.com/Standard_Model.pdf
However it is not comprehensive and only gives the gauge symmetries (and does not explicitly give their corresponding currents)

*edit* that is a very interesting paper, thank you (and it's a very well written, thorough description of the entire SM). It does have some of what I'm looking for, but it doesn't have the associated conserved currents that arise from the symmetries.
 
Last edited:
By Coleman Mandula's theorem, we know that the symmetries are Spacetime X gauge... so in explicity, Poincare and Gauge Symmetries...So...
First of all the Standard Model is a Yang Mills gauge theory of SU(3)C x SU(2)L x U(1)Y, so I don't think you can find more kind of gauge symmetries in it. Of course you can go around playing with them, imposing some symmetries for the theory you want to make (eg impose a Z symmetry to forbid the decay of protons).

A physical theory though should also be Lorentz invariant, so you can also impose the Poincare symmetry.

As for the conserved currents now, you need to know the generators of your symmetries. For example in the Lorentz Group you have rotations and boosts (corresponding to conserved current for momentum and "generalized" angular momentum). The Lorentz group leads to chiral symmetries, since the proper orthochronous Lorentz Group is isomorphic to SU(2)xSU(2).
For seeing the conserved currents, just use your group generators in exponential, try an infinitesimal transformation of the field and use the Noether's theorem to find the conserved current as well as the conserved charge.
I have never tried it, so I can only guess.. The thing that must not change is the charge (combination of SU2 and U1), the color, and maybe something with the isospin...
 

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