Recent content by rbphysics

The lesser Green's function is defined as: $$G^{<}(t,t')=i\langle C_{\nu}^{\dagger}(t')C_{\nu}(t)\rangle=i\bra{n}C_{\nu}^{\dagger}(t')C_{\nu}(t)\ket{n}$$ where ##\ket{n}## is the many particle ground state...

The commutator of [x,p]=i$\hbar$. Is it a postulate? No book state it as postulate of Quantum mechanics. But, I don't see anything more general by which I can derieve this. At elementary level Quantum mechanics, one start with momentum operator in position representation to derieve this. But...

This is often stressed in QFT books that concept of antiparticle is required to preserve causality in QFT. I don't understand it. Moreover, It is also mention that the propagator G(x1,x2) for timelike separtaed events give probablity amplitude for particle to travel from x1 to x2 if t2>t1 and...

I request anyone to clarify the same. Causality in QFT and need of antiparticles. And, Non vanishing Propagator outside the lightcone.

Hiii everyone! I am starting my PhD in theoretical condensed matter and has started to learn QFT and many body physics. I hope to ask and answer a lot of questions.

Is there any other book that discuss the same like Padmanabhan. Given that he starts with path integral and lots of maths. It's somewhat difficult to follow.

The Causality in QFT is said not be violated by showing field operators in Klein Gordon field commute outside the light cone. This is necessary because If I here measure a observable A and my friend there at mars measure observable B that does not commute with A then he can influence my...