Recent content by pscplaton

Thanks for your reply. But then I don't understand why the double bubble diagram has a symmetry factor of 2. According to what you are saying, it should have a symmetry factor of 4, shouldn't it ? edit: Sorry I was confused. It works. There is actually a symmetry factor of 8

Yes you are right. I mean that like "a", "d" can only be mapped to itself, because it has a hermitian propagator loop attached, and this is the only hermitian propagator loop of the diagram

Hello ! In the book Quantum Field for mathematician, there is this Wick diagram as an example to understand how to compute the symmetry factor (I am sorry, I draw it with paint...) This is about a hermitian field interacting with a complex field. The book says it has a symmetry factor of 2...

Thanks for your replies. I will have a look to these references

Hi All, The S-matrix is defined as the inner product of the in- and out-states, as in Eq. (3.2.1) in Weinberg's QFT vol 1: S_{βα}=(Ψ−β,Ψ+α) \Psi_{±α} are the eigenstates of the full Hamiltonian with a non-zero interaction term. Can \alpha describes a neutron ? Since it is not stable, it is...

Hello! I am a second year master student in theoretical physics and I have a lot of questions about QFT. I like chocolate and listening to music as well.