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 Posted: Fri Aug 03, 2007 5:57 am
So, my plan was to go in to particle physics, but recently someone at work warned me against that. He is a post-doc and started out in particle physics but then switched to biophysics, and he said, that there was nothing new going on in the field, that there have been no new discoveries since the standard model and most of today's research is built around reducing the error bar. He also said that those who go into it, go in to do a lot of work for little gain. Is this true?
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Posted: Fri Aug 03, 2007 7:48 am
The standard model is not perfect. We already know that it is insufficient to deal with neutrinos [massless in the SM, experiment saying they have mass eigenstates]. There there is the problem that no one has found the Higgs yet and we are slowly eating into the most likely section of parameter space.
What does no discoveries since the the standard model mean? [There have been observations of new objects consistent with the SM long after the SM was originally proposed.] Reducing the error bar is the only way you can find out if there is new physics [you need to have a disagreement with the SM to know that something else is there, that can only be done if you can remove enough uncertainty].
I suppose it boils down to a value-judgement about what is worth your time.
I know I am biased. It depends on what you want to do.
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Posted: Fri Aug 03, 2007 9:44 am
well I'm sure he was biased too. He didn't tell me very maturely, only brashly said to not go. Do you think that with the LHC and possibly the ILC coming our way, there might be a surge of particle physics research?
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Posted: Fri Aug 03, 2007 11:38 am
The ILC is never going to happen: it is too expensive for the gains. A muon linear collider is more likely, but even that is decades of research away.
The LHC is going to be the centre of collider based research, but look out for the long-baseline experiments which are looking to measure/constrain the PMNS matrix.
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Posted: Fri Aug 03, 2007 5:47 pm
The particle physics world needs either:
1) People clever enough to devise experiments capable of proving or falsifying String/M-Theory
2) People clever enough to come up with the mathematics that'll allow for the right "compression" of the extra dimension in that theory, or who are able the deduce the underlying principles that are the rationale of that theory.
I wouldn't be surprised if such a person would have to be more of a genius than Einstein, Hawkings and Edward Witten combined...
But trust me, the historical record is sufficient proof to tell you that whenever a scientist claims work in a particular field is through and there's nothing more to be done, he's full of s**t.
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Posted: Fri Aug 03, 2007 6:33 pm
Cynthia_Rosenweiss The particle physics world needs either: 1) People clever enough to devise experiments capable of proving or falsifying String/M-Theory 2) People clever enough to come up with the mathematics that'll allow for the right "compression" of the extra dimension in that theory, or who are able the deduce the underlying principles that are the rationale of that theory. I wouldn't be surprised if such a person would have to be more of a genius than Einstein, Hawkings and Edward Witten combined...But trust me, the historical record is sufficient proof to tell you that whenever a scientist claims work in a particular field is through and there's nothing more to be done, he's full of s**t. well not that there is no more work to be done, just that there isn't much varying work and not very many opportunities. It seems by your description it's a race for two things, I mean if you were to be part of that, how much of that would be yours? you as general, not you cynthia particularly.
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Posted: Fri Aug 03, 2007 7:23 pm
Are you looking at experimental or theoretical? Because a theoretical answer to why the U(2) symmetry of electroweak is broken other than "durr, the Higgs did it" would be nice. I mean, the U(1) of electromagnetism and the SU(3)/Z_3 of QCD look to be exact, so why was the weak interaction singled out?
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Posted: Fri Aug 03, 2007 8:14 pm
Layra-chan Are you looking at experimental or theoretical? Because a theoretical answer to why the U(2) symmetry of electroweak is broken other than "durr, the Higgs did it" would be nice. I mean, the U(1) of electromagnetism and the SU(3)/Z_3 of QCD look to be exact, so why was the weak interaction singled out? I'm pretty sure that it's the SU(2)xU(1) isospin-hypercharge symmetry that is broken and that the U(1) of QED is not the same as the U(1) component in the mixed electroweak force. Before the symmetry is broken QED does not exist [the photon and Z are mixed up as the W_3 and B fields]. I think.
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Posted: Fri Aug 03, 2007 11:38 pm
A Lost Iguana Layra-chan Are you looking at experimental or theoretical? Because a theoretical answer to why the U(2) symmetry of electroweak is broken other than "durr, the Higgs did it" would be nice. I mean, the U(1) of electromagnetism and the SU(3)/Z_3 of QCD look to be exact, so why was the weak interaction singled out? I'm pretty sure that it's the SU(2)xU(1) isospin-hypercharge symmetry that is broken and that the U(1) of QED is not the same as the U(1) component in the mixed electroweak force. Before the symmetry is broken QED does not exist [the photon and Z are mixed up as the W_3 and B fields]. I think. The group is technically SU(2)xU(1)/ Z_2, but it's equivalent to U(2) and U(2) really gives a better description of the symmetries. Sure, the U(1)_em is actually generated by Y/2+I_e, Y/2 from the SU(2) and the I_e from the U(1). That's not quite the point. Although there should still be somewhat of a QED even from an unbroken symmetry, in that there is still the U(1) subgroup to give us something akin to a photon.
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Posted: Sat Aug 04, 2007 6:49 pm
There's a little rule in my head that says to not argue with Layra about mathematics. I shall follow the rule. Though, as my specialisation is in electroweak physics — I've worked on W width, now working on W mass — this is s**t I really need to have nailed down slightly better [it's a little tricky to avoid the Higgs mechanism when motivating a W mass measurement].
Is SU(2)xU(1) isomorphic to U(2)? Blaaaaah, too long since I studied group theory. Well, U(2)'s the Lie algebra gives you four elements like with SU(2)xU(1). crying
This is why I am not a theorist. sweatdrop
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Posted: Tue Feb 24, 2009 1:40 am
Well, if you have enough imagination, it is not end of this physic.
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Posted: Tue Feb 24, 2009 5:08 pm
poweroutage He is a post-doc and started out in particle physics but then switched to biophysics Strange... The same thing is happening to me, in a way.
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Posted: Thu Feb 26, 2009 5:20 pm
A Lost Iguana Is SU(2)xU(1) isomorphic to U(2)? Blaaaaah, too long since I studied group theory. Well, U(2)'s the Lie algebra gives you four elements like with SU(2)xU(1). crying This is why I am not a theorist. sweatdrop I don't think it is. You have the natural homomorphism SU(2)xU(1) --> U(2) (M,z) --> zM but this is a double cover. (-M,-z) and (M,z) map to the same zM. So, I think U(2) is isomorphic to SU(2)xP(1), where P(1) is the real projective line U(1)/{1,-1}. This makes sense, since the determinant of zM is |zM| = z^2 |M| = z^2 so that if we wanna go backwards from U(2) to SU(2)x(something), we need a unique square root of z^2, which we can't have on the whole circle.
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Posted: Sat Feb 28, 2009 1:26 am
Right, so there's an isomorphism between U(2) and SU(1)xU(1)/Z_2. Since the theory deals mostly in terms of the Lie algebras, though, it doesn't really make a difference.
Having now taken a course on Lie algebras and particle physics, it appears that the Higgs is scalar field of some sort that distinguishes a particular generator of the U(2) and thus causes a decomposition of the U(2) into an SU(2)xU(1)/Z_2. Although at the moment I only really know of it in terms of an SU(5) quark-lepton unification, being that the course was taught by Georgi.
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