Recent content by izh-21251

Hello, everyone! I have a short question. I think everybody knows the Furry theorem for QED, which tells, in particular, that fermion loops with odd number of fermions always give 0. Does the same true for QCD of weak theory? Can one have non-zero contribution to 3-gluon vertex (or 3-boson...

All objects that have energy do interact gravitationally... Since E=sqrt(m^2+p^2), there are no observable particles with 0 energy. So all particles (including massless) are subject to gravity.

By the way - the same properties (scalarity or non-scalarity) one can observe in particle representation - via considering properties of particle operators due to Lorentz-transformations. Refer to S.Weinberg, "The quantum theory of fields", Volume 1, Chapter 5.

Let me argue. Usually, the Hamiltonian density has the property: U(\Lambda, a)H(x)U^{-1}(\Lambda, a)=H(\Lambda x+a) (1) then one says that Hamiltonian density is a scalar. Here U - is a Lorentz transformation. Did you mean U(\Lambda, a)H(x)U^{-1}(\Lambda, a)\neq H(x) ?? This is of...

Dear Eugene, sorry for delayed reply. I unfortunately had a plenty of work lately. I spared some time to revisit your book. Concerning \Lambda_{2}, you are right, I apologize for a mistake. This constant enters renormalization term in conventional S-matrix approach, so it is a C-number and...

My point is that \Lambda_{2} is not a C-number. If I suppose it is a C-number, I cannot cancel the renorm operator of second order in Hamiltonian. Ivan

When explicitely perfoming dressing transformation in QED Hamiltonian in Coulomb gauge, I faced the problem that 2-nd order renormalization operators do not cancel mass counterterms. In other words, I obtain mass shifts (say, for electron) that depend on particle momentum and different in...

Hamiltonian and Boost-generator do not commute. That I undestand. That's why moving objects look differently from static (have larger energy, show time delay, length shortening etc.) What I tried to ask is, whether the UNUSUAL properties of interactions in Hamiltonians (consisting in that...

Let me be more specific.. What is the nature of these factors - \Delta_2 and \Lambda_2 ? Are they the C-numbers?

I suppose it's ok with respect to the S-matix - it is the same QED S-matrix for Hamiltonians in all Lorentz frames. But what about time evolution? Won't these Hamiltonians (containing interactions which look different in different Lorentz frames) lead to different time-evolution laws...

Yes, I probably was not accurate enough in my point. I meant, that the product \epsilon_{i}(\acute{s},\acute{k})a(\acute{s},\acute{k}) (where a is the photonic operator) changes it's form under any boost in the plane, orthogonal to \acute{\vec{k}}, so that additional term. proportional to...

I think we are in total agreement here. There is no physical meaning in 'gauge invariance'. I will try to avoid using term 'gauge invariance' in discussing particle theory... since it causes a lot of misundersatndings.

This procedure is equal to the case, when I take field-theoretical Hamiltonian (leading to the QED S-matrix) and apply dressing transformation to it, isn't it? The two Hamiltonians are scattering-equivalent - the second (dressed) Hamiltonian lead to the same S-matrix.

Exactly what I meant. If you apply boost to the interaction operator (14.70), page 546 in the book, the photonic coefficient function won't stay unchanged - an additional term, proportional to \acute{k}^{\mu} will occur. So, instead of \epsilon_{i}(\acute{s},\acute{k}) (in your notations) one...

Sorry, I edited my post too long, so you answered it earlier than I finished it. )) Ivan