Recent content by moss

Of course, like in Sakurai where he said that we impose commutation relations on compatible observable but what is compatible in QFT? and why commutation relation, why not anti-commutation relation? Further 2 operators can commute maybe due to some missing info, redundant dof? My knowledge is...

For example, Peskin&Schroeder says in 2.3 that field quantities goes to operators and suitable commutation relation are imposed, so what is suitable? and are there any other motives than just to quantize the theory?

Hello everybody, In all QFT courses one starts very early with commutation and anti-commutation relation. My main question is why do we do this and what is the motivation? I have already asked few people including our professor but could not get a clear answer. I am talking about the...

Very nice example. But after the Qs. of symmetry breaking another natural Qs arises that is annoying me for sometime that ; How can a fake symmetry (gauge symmetry), when broken , generates real masses ? If SSB is just a realization of a system with no energy input/output then how can it has a...

Thank you guys, this may be the essay I was looking for. It addresses just the right Qs. e.g how can a symmetry which is not a physical symmetry, produces physical results upon breaking. The textbooks like Ryder, Peskin, Cheng-Li and Huang are not addressing the Qs. I have therefore this essay...

THANKS Chris ! in the abstract of the article are the same Qs. I am asking and nobody is addressing the real issue that how just a realization of a ground state can have real physical results. I will certainly read this article tonight. The term SSB is quite common among physicists but not...

Thanks for the reply. last week I asked the same thing from a very senior Prof. and his answer was that watch out the english words as its a realization of the ground state. He explained to me something but I did not understand and not to be embarrassed I said that I do understand. My english...

Having read different text on SSB but still I have no clear concept of what or which symmetry breaks in SSB, abelian and non-abelian theory. What do we mean by term SSB? all I see is the symmetry of ground state is broken but the lagrangian and the given potential is still symmetric under local...

Okay the original Qs. with V=vector particle and S1 & S2 are spinless is that; Let V--->S1S2 in the rest frame with S1 emitted in the x-z plane at and angle theta respect to z-axis. show that the decay rates for polarization states of V with spin Sz=+1,-1,0 along the z-direction are...

Thanks for the reply, so e.g for Sz=1 what polarization vector should I use assuming the axis is z.?

Hi All, I want to understand the decay of a spin-1 massive vector particle into two spinless massive particles. Given a massive vector particle V with spin Sz = +1, 0, -1 decays into 2 massive spinless particles. I have to compute the amplitude M but I don't know what should I do with the...

Thanks mfb...it is about 10 years I did all that and forgot and the funny thing is that link above of Feynman lectures, same thing is collecting dust in my bookshelf.

Please confirm; For the same final state we add amplitude and then compute probability, even if the final state is reached thru different Feynman diags. with different coupling constants. For different final states (helicity staes) we compute probability separately then add ...Right??

You mean that e.g the chiral electron+positron -->muon+anti-muon one has to sum the amplitudes of all the polarized out-coming muon and then compute probability? what about first computing the probability and then adding them? My qs. is based on Peskin & Schroeder 5.22 till 5.24. This is...

Hello guys, Suppose a process 1+2--->3+4 proceeds thru 3 different intermediate particles and has 3 Feynman diagrams. When we compute the probability then what does the cross terms( interference ) mean? and do we have to always compute the cross terms? What I mean is that when you have 3...