Recent content by simonjech

Thank you very much for the clarification.

Thank you for your respond. Can you also please explain why it is impossible to fulfill causality without using fields?

I am learning QFT rn, so the question that I naturaly ask myself often is why do we have to use field operators in relativistic quantumn theory instead of operators with finite number of degrees of freedom which are used in non-relativistic quantumn mechanics? One of the reasons that I came...

I think that it is quite nice tool when we can decompose any field into a set of harmonic oscillators. One of the reasons is that we can solve the harmonic oscillator problem in QM completely analytically. No perturbation theory or variations or any numerical method.

Because we can write any field in qft as a superposition of plane waves.

I think that you mean the Stern Gerlach experiment here where atoms of silver went through an inhomogenious magnetic field and the magnetic force acted on them even when these atoms were neutral. In classical physics this would not make any sence because classicaly, the magnetic moment of a...

You dont really need to use spin to explain this. Magnetic force can act on any charged object which has non zero velocity. And we can define spin using Noethers theorem as a quantity which is conserved when lagrangian is symetric under the lorentz transformation (boost). If you analyse this...

I think that i figured it out. The problem was that I did not realized that .

This is the part of Schwinger-Dyson equations derivation. I did not understand how can we obtain the commutator in the last line of the picture. I understand why the delta functions appeared from Heaviside functions but there is no minus sign in any term so how can we get the commutator...

Thank you for your respond. It was helpful to me.

Yes, f means final. Can you please be more specific?

Can someone please explain to me how can we obtain this integral in eq. 5.27 from eq. 5.26? I quite do not understand how is it possible to make this adjustment and why the (p_(f))^2 appeared there in the numerator and also why a solid angle appeared there suddenly.