Meir Achuz

g and g' look like 2 ccs, just like q_esu and q_emu. That is before unification. After unification, each case has one cc: alpha, and a mixing parameter: v/c or theta_W. Pedants argue over words.

"I did have the equivalent of a freshman course in mechanics". That's not enough. Wait till you've had the second level UG course before trying G on your own.

It's best to learn physics, step by step. You need a good graduate basis in EM and QM to start QFT.

I would wait until after your UG course in mechanics. If you've done that, then enjoy.

Your first eq. is wrong (besides the misprints). The second equation is correct.

What does that mean?

"The plain attraction of ferromagnetic material always is present and results in a net attraction." That is about what is happening. A magnet will attract non-magnetized iron as strongly as if it were magnetized. A better way of seeing it is to note that the attractive force between two bar magnets is stronger than the repulsive force (if put N to N). This is because there is a demagnetizilng field when put N to N.

You could go to this website for a brief discussion: aether.lbl.gov/www/tour/ elements/stellar/strong/strong.html I recommend avoiding wikipedia. The best thing would be to look at a nuclear physics (or "modern physics") text.

I'm afraid I got ahead of you. You really need the Dirac equation (in relativistic QM) to understand the V-A theory. You could get some idea from a book on modern physics or a text on "weak interactions".

I just noticed this question. The answers are Yes and Yes.

It is not called "asymptotic freedom". (You must have read Marlon.) The confinement of quarks is called "confinement" or "infra-red slavery". The long distance force between quarks is now believed to have the form V=kr, leading to confinement. The property of "aysmptotic freedom" is that at small distances (<<1fm), the strong forces weakens. It is called AS because small r is related to high q^2, so the force asymptotically goes to zero as q^2-->infinity. The bag model was an early model of confinement, but now the linear form is more favored.

The electron spin direction in beta decay has nothing to do with magnetism. The V-A nature of the weak interaction makes the helicity of the electron H=-v/c.

For a bar magnet, the proof is very simple. It also works for a solenoid. Place two bar magnets touching end to end (N facing S). The B at their interface comes equally from each magnet, and so is twice what you would have if one magnet is pulled away.

The 1.23 would be the field between two such bar magnets, which equals the B at the center of one bar magnet. B at the end of a bar magnet is one half the B at the center, so you measure one half of 1.23.

Most texts don't do this. In order to push two bar magnets together would take a force F=2\pi MM'A, where M and M' are the magnet strengths in gauss, A the area in cm^2, and F is in dynes. Actually, the force would be somewhat less than this due to the demagnetization, which depends on the actual material of the magnets.

I can see you are thinking, but there is a resolution. The force on one plate of a capacitor is not \sigma AE. It is one half of that because E is due to both plates, but the force on plate 2 is only due to the E from plate 1.

Even if there were no demagnetization of the weaker magnet, the ratio of forces would be 5/4.

No. The force would be greater in the first case. When a strong magnet faces a weaker magnet, N to N, the stronger magnet tends to demagnetize the weaker magnet. A strong N opposite a weak enough N can even attract.

The word "scale" is used to make clear that an exact value for the energy is not meant. You might say that "the population of the Earth is at the GeV scale", even though 6 GeV is closer. "Electroweak scale" means energies at which the weak interaction is "of the order" (which usually means within about 10%) of the electromagnetic interaction.,

There are two ways to measure the mass of a photon. (Actually to put limits on it.) 1. If the photon had mass, photons of different energies would have different velocities. Any (speculative) photon mass is ceertainly so small that this is a difficult measurement. Observing photons from a supernova would give one limit, but probably not a very low one. This method was tried for the neutrinos from SN1987a (If I remember it right), with mixed interpretations. 2. Since one photon exchange is responsible for the Coulomb force (using QED), any variation of Coulomb's law at large distance from 1/r^2 would indicate a mass of the photon. This gilves the most sensitive limit on the photon mass. From this type of experiment, an upper limit of mass(photon)< 2X10^{-16} eV has been set.