# Tag Info

2

There are two SU(3) symmetries you can come across. Basically, SU(N) emerges everywhere when you have N quantum states and some physics does not distinguish these states - then all quantum superpositions of these states make a fundamental representation of SU(N) significant to that physics (but maybe insignificant to some other). Thus in particle physics ...

2

No, the colorful $SU(3)$ of QCD is not broken. However, it is confining which means that all physical objects that may exist in isolation have to be neutral (singlets, invariant) under the whole $SU(3)$. Objects that are charged (not neutral), like the quarks themselves, behave as "individual end points of a rope" and they always try to produce a flux tube ...

2

First of all is the definition of coupling constant: In physics, a coupling constant, usually denoted g, is a number that determines the strength of the force exerted in an interaction. Usually, the Lagrangian or the Hamiltonian of a system describing an interaction can be separated into a kinetic part and an interaction part. The coupling constant ...

0

This is different from the possible time-variation of the low-energy fine-structure constant, but the same considerations apply when you try to attribute any such variation in $\alpha$ to a variation in $e$, $\hbar$, or $c$. You can't. See Duff, "Comment on time-variation of fundamental constants," http://arxiv.org/abs/hep-th/0208093 . I also don't see why ...

-2

The so-called unified is saying that the coupling constants of three different forces are the same one when the energy scale goes to high enough. Those coupling constants are not really constant because they are changing when the energy scale goes up or down.

11

If you want to print it on a T-shirt - print the Lagrangian of the Standard Model - then the T-shirt has already been printed and it looks like this: http://www.flickr.com/photos/joshmt/7503048090/ The physicist on it is John Ellis, the 2nd most cited living particle physicist. Of course, the terms could be elaborated upon, written a bit more ...

2

Nielsen identifies a quantity, a ratio of "Casimirs", which he thinks is maximized by the particular gauge symmetry groups and space-time symmetry groups that we see. He has previously had the idea that some of the observed properties of physics are "random" or "accidental" - e.g. that there is some complicated deeper theory and the simple observed ...

0

The fermions are mixed by off-diagonal elements in the Yukawa matrices, which result in off-diagonal elements in the up- and down-type quark mass matrices. Diagonalising these mass matrices results in the mass eigenstates identified with the observed quarks. Because the Higgs-quark couplings are proportional to the Yukawas, they are diagonlised by these ...

Top 50 recent answers are included