Penrose objection?


by torquil
Tags: book, electroweak, gauge theory
torquil
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#1
Jan24-10, 06:00 PM
P: 640
Hi! This is for those who have read Penrose's "The Road to Reality" (btw, fantastic book).

In paragraph 25.8, on page 651, he writes something that I interpret as a critical remark regarding the spontaneous broken electroweak gauge symmetry.

Quote ( btw, he writes U(2) instead of the usual SU(2)xU(1) ):

"Also, there is the rather strange asymmetry between the roles of SU(3) and U(2) - in that SU(3) is taken to be exact, whereas U(2) is severely broken. Indeed, in my view, there does appear to be something strange about the particular way that U(2) is taken as a 'gauge group', which would seem to require an exact unbroken symmetry...."

Is he alluding to some problem regarding the EW theory that he does not write explictly? What does he mean by "... the particular way that U(2) is taken as a 'gauge group'"?

Anyone know/understand?

Best regards
Torquil
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clem
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#2
Jan25-10, 10:33 AM
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A gauge theory requires massless vector bosons. The vector bosons of weak interactions are massive (to the extent the 80 GeV is not negligible). By forgetting this, G, S, and W won the Nobel prize.
George Jones
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#3
Jan25-10, 11:20 AM
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Penrose doesn't like gauge symmetry breaking.

For Penrose's perspective, read the two sentences At the bottom of page 652 that begin with "The conventional perspective on electroweak ...," and then read sections 28.1, 28.2, and 28.3.

torquil
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#4
Jan25-10, 12:20 PM
P: 640

Penrose objection?


Quote Quote by George Jones View Post
Penrose doesn't like gauge symmetry breaking.

For Penrose's perspective, read the two sentences At the bottom of page 652 that begin with "The conventional perspective on electroweak ...," and then read sections 28.1, 28.2, and 28.3.
Ok, thanks. I'm in chapter 27 at the moment, so I'll have it in the back of my head when I get to those sections.

Torquil
torquil
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#5
Jan25-10, 01:44 PM
P: 640
Quote Quote by clem View Post
A gauge theory requires massless vector bosons. The vector bosons of weak interactions are massive (to the extent the 80 GeV is not negligible). By forgetting this, G, S, and W won the Nobel prize.
From wikipedia:

"In 1963 American physicist Sheldon Glashow proposed that the weak nuclear force and electricity and magnetism could arise from a partially unified electroweak theory. In 1967, Pakistani Abdus Salam and American Steven Weinberg independently revised Glashow's theory by having the masses for the W particle and Z particle arise through spontaneous symmetry breaking with the Higgs mechanism."

So maybe you could say that Glashow forgot it, then Salam and Weinberg remembered it later on :-)

Hopefully the LCH will be able to shed some light on the Higgs mechanism.

Torquil


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