Recent content by metroplex021

Thank you Reggid. Is this consistent with what Orodruin writes above - ie what we're measuring when we measure this 'running mass' is something different from the mass of bottom quark itself?

Thank you Orodruin. I thought the pole mass was just the mass of the *free* particle in its own frame -- which is why, given confinement, the pole mass isn't well-defined for quarks. And I thought that the 'running' mass of the particle was its effective mass when undergoing interactions at...

Hi everyone, I understand that the phenomenon of running charge predicted by QFT has been experimentally verified: the physical charge on an electron really does vary with the energy at which it is measured. I have two questions: (1) Does anyone know what the canonical experiments confirming...

Thanks for the video! What a great resource.

that's a really wonderful answer. Thank you! Going to try and digest it a bit, and get back... But thanks so much!

Hi all -- can anyone offer a qualitative explanation of why it is that couplings run with the energy in *relativistic* quantum theory, and not in non-relativistic? Some insight here would be much appreciated. Thanks.

Thank you, The_Duck. A final question: it seems strange to me that a particle can undergo an interaction without some interaction property to couple to. (In the case of real interacting theories, for example, we have properties like charge, color, and weak isospin in addition to their...

I'm looking at the simplest example of an interacting theory, and this is the theory of a neutral scalar boson $\phi$ with $\lambda \phi^4$ interaction term. Can I ask: is there a physical interpretation of the `charge' through which this field interacts with itself? In particular, is \lambda...

Thanks a lot. I appreciate that of course we can't measure an electron in the absence of interactions, but I'm wondering if it even makes theoretical sense to ascribe a charge to a field occurring in a free theory. Of course there will be a global U(1) charge in this case, but it seems to me...

The question is in the title: is it possible for a theory to be both UV and IR stable? And concrete models would be much appreciated!

Sure -- but then we talk about 'the charge on a free electron' all the time, and I'm wondering how this is defined. Maybe another way to ask the question is this: given that we take QFT to admit free-field models, are any of these models in which electrons have charge? Here's why I'm...

The_Duck, Susskind discusses mass renormalization in a way that aims to be intuitive here: . (In case that's of interest!)

Hi there, I have a question about the definition of a charge of a free electron. Let's suppose that QED is the true theory of the interactions of charged particles. Presumably the charge on an (effectively) free electron, then, is the charge on an electron in which the electromagnetic...

Thank you very much TheDuck. A final question. You phrased your claim regarding the physicality of running couplings in terms of alpha, the charge parameter. But just to confirm, would you regard the running of mass as as 'real' as the running of charge? Thanks again though -- really...

Thank you very much The_Duck. That's tremendously useful. One last thing (if you're still around!). At times you make it sound as if the mass 'running' is just an artefact of the renormalization scheme. However, am I right in thinking that we have actually measured that the masses (sometimes...