Recent content by Xiaomin Chu

Thanks very much. ##\phi^3## theory is just a toy before going to QED. He actually introduces Feynman rules in Part I, not ##\phi^3## theory. Is it possible to skip some sections and go directly to QED?

QED,,,I'm not sure whether Srednicki has introduced QED in his book. He talks a little about photon field and eletro-dynamics. After all I'm learning QFT from his book. Are there any good books on QFT(or StringTheory) other than Srednicki's? I may need more books.

I guess phi-cubed theory is super-renormalizable in 4 spacetime dimensions so the calculations will be easier. Phi-4th-powered theory is well-defined and just right, but it needs especially careful treatments. Another question is, which L1 best describes the process of a photon creates an...

Sometimes physics seems incorrect mathematically, that's because the current mathematics doesn't include the objects physicists use. I believe physics includes two sides, one is experiments, that goes from "top" to "bottom", the other is mathematics, that goes from "bottom" to "top". When they...

I'm learning QFT from Srednicki's book. He introduces dimensional analysis in section 12. Coupling constant needs to be dimensionless in order to avoid a number of problems. So phi-cubed theory needs 6 space time dimensions to make sense, but isn't phi-4th-powered theory just right for our 4...

Can you tell more mathematical details about this? I'm not satisfied by Srednicki's introduction, I want strict mathematics.

There are always some functions that remain discontinuous when being broken to pieces. In fact there are " much more" this kind of functions than continuous functions, "almost every" function has this property. Does that mean path integral will not even converge?

Somebody asked about this but that thread was closed very soon. In physics, discontinuous paths breaks locality so they must be 0; but mathematically, they causes some problems. Discontinuous functions must not be differentiable, so it's impossible to calculate the action over that path. However...

Thanks

Thanks

Thanks. Is this correct:? A state vector is a vector in a Hilbert space which is the tensor product of a CSCO's space. Each operator in CSCO operates on its own indices, so position and spin operators do not affect each other. Then another problem, just the same as entanglement: tensor product...

You mean, tensor product?

Then how can spin operators represented by 2X2 matrices act on the countably infinite dimensional vectors to have eigenvalue equations?

Often ignored, but turned out to be a problem when trying to compute the commutator of position and spin. Pauli matrices clearly acting on two dimensional vectors while position on infinite dimensional vectors. But a system is described as a single state vector in Dirac notation. A system can of...

Thanks a lot!