# Recent content by joneall

1. ### A Simple definition of Lie group

Good point, thanks. However, I am not trying to define a Lie group. I can do that but it's not my intent. I want to condense down to the real minimum of saying why we bother with them and how they can help us. Apparently, this is too minimal.
2. ### A Simple definition of Lie group

I'm writing some notes for myself (to read in my rapidly approaching declining years) and I'm wondering if this statement is correct. I"m not sure I am posting this question in the right place. "Summary: The matrix representations of isometric (distance-preserving) subgroups of the general...
3. ### A Frame fields

That's what I thought. But Rovelli does not mention them. They are not in the index. Maybe you are suggesting I drop the book...?
4. ### A Frame fields

I'm having trouble with Rovelli's new book, partly because the info in it is pretty condensed, but also because his subjects are often very different from those in other books on GR like the one by Schutz. For one thing, he never uses the term "manifold", but talks about frame fields, which seem...
5. ### A Why does D(1,1) representation of SU(3) give baryon octet?

Thanks, but that does not answer my question. Greiner uses 1 quark and 1 antiquark to construct the 10-d SU(3) octet, then uses it for mesons and baryons. Is there a better way of constructing the baryon octet? Preferably without my purchasing yet one more QM book. (I don't have access to a...
6. ### A Why does D(1,1) representation of SU(3) give baryon octet?

The question may be ambiguous but it's really simple. One says that the baryon octet is the D(1,1) representation of SU(3), but then uses the same one for mesons. D(1,1) means one quark and one antiquark, which corresponds perfectly to mesons. But how can it explain baryons? My information and...
7. ### A Justification for phi^4 potential

Interesting. Where is the gauge theory in GR? For my limited understanding, that would be thru the use of the covariant derivative with Christoffel symbols as connections. But that hardly looks like a new field to me.
8. ### A Justification for phi^4 potential

My understanding is at the level of Griffiths's Introduction to quantum mechanics or Robinson's Symmetry and the standard model, i.e., using the phi^4 potential to explain the effects of global and local symmetry breaking, Goldstone and Higgs bosons. These books and others use a potential of...
9. ### I Gauge theory symmetry breaking in L&B

Thanks for you explanation, vanhees71. In fact, the sign of the mass term is intentionally chosen "wrong" so as to go thru what you explain. You give somewhat more detail, tho, so thanks.
10. ### I Gauge theory symmetry breaking in L&B

Ok, that sounds good. Thanks a lot.
11. ### I Gauge theory symmetry breaking in L&B

Thanks for the tip about the dagger. I know about the ## F^{\mu \nu}F_{\mu \nu} ## term being a photon, but can it represent two of them? How do we know?
12. ### I Gauge theory symmetry breaking in L&B

I’m reading Lancaster & Blundell, Quantum field theory for the gifted amateur (even tho I”m only an amateur...) and have a problem with their explanation of symmetry breaking from page 242. They start with this Lagrangian: ## \mathcal{L} = (\partial_{\mu} \psi^{\dagger} - iq...
13. ### I Where do wave functions come from?

In classical mechanics, we have either Newton’s laws or a Lagrangian in terms of coordinates and their derivatives (or momenta) and we can solve them for the behavior of the system in terms of these variables, which are what we observe (measure). In QM, we quantize classical mechanics by making...
14. ### A Symmetry of QED interaction Lagrangian

Uh, isn't there a way to mark a thread "Answered" or "Resolved"?
15. ### A Symmetry of QED interaction Lagrangian

Your equations look good to me. (I envy you. When I did grad work in <1965, there was no course offered in group theory, which is why I'm struggling some now.) Interesting that I have never seen in any of these books what you just went thru. So it all is U(1), it just looks different in the two...