Recent content by mings6

In QFT equations, there are not only positive energy solutions, but negative ones as well. Dirac had the hole theory. But the sea may have infinite charges and gravity effects. And then QFT textbooks just explain the negative solution as anti-particle. But in the lab, we measure the...

If we want to solve the \lambda \phi 4 equation in the same way as solve the Dirac equation, I think we should normalize the result. So we can say that the trivial expresion of <initial | final> = <\phi|\phi>=1 means, when no perturbation, the amplitude from \phi to its own is 1. For instance...

In quantum mechanics, most wave functions are normalized with \int |\phi|^2 dx^3 =1. But I did not see any field in the quantum field theory is normalized. I understand they maybe just plain waves and does not need to be normalized. But in some cases, if we do not expand the field as plain wave...

thanks

For the simple harmonic oscillator case, the energy is E=(n+1/2)hw, and N|n>=n|n>. It seems second quantization explain it as there are n bosons with each particle has energy homework plus vacuum 1/2hw. But we know before second quantization, there is only one particle with energy nhw plus...

In atom spectrum, such as for hydrogen, there are states of 1s, 2s, 2p, 3s, 3p, 3d, etc. There are no 1p, 1d or 2d, 2f. Simply because n= n_r + L +1. So the maximum of L is n-1. But when I read articles talk about meson, they list meson states of 1p, 1d, 1f, etc. Such as in the article “Quark...

Sorry for a naive question. In EM textbook and QM path integral textbook, the action and Lagrangian in electromagnetic interaction are S = L dt = e(\phi – A v) dt ---equ.(1) But in QFT textbook, the action and Lagrangian density are S = L d^4x = A J d^4x ---equ.(2) As I...

Thanks for reply. I still do not understand, if general relativity can not model spin-orbit coupling, then how can we have the Kerr metric that describes the geometry of spacetime around a rotating massive body? And also Gravitoelectromagnetism can do some jobs for frame dragging and the...

Who’s “spin” is in the Einstein-Cartan theory? Source’s spin or the test particle’s spin? I quantum mechanics, when we say spin orbit interaction, such as in hydrogen atom, it’s about the test particle's, the electron’s spin and the electron’s orbit interact to each other. In the...