@DanielSank ooh, right... that's a bit of physics I haven't seen in a loooong time. I guess you could say that, yes. Though I don't think the intermediate states are quite the same as virtual particles - each state can have multiple virtual particles in it. If I remember right.
There is certain problem in formulating e-mails to strangers, I agree. If you are too brief, they are likely to misunderstand. If you are too elaborate, then the mail becomes confusing.
@DanielSank Only if you ignore things like Haag's theorem. There is a fundamental issue in QFT that the interaction picture from standard QM doesn't really work (although you can use it to get correct first-order results in many cases)
@ACuriousMind I really think all this business about Fock states in the interacting system not existing etc. etc. is a perfect example of letting the perfect be the enemy of the good enough.
@ACuriousMind Because when 99% of mathematicians/physicists say they know "nothing" or "very little" about something, they mean they don't know as much as someone who specializes in it
The notion of virtual particles is just that of excitations we find on the insides of our pictures of physical processes, but which never make it to the outside.
You can see that in the Schrodinger equation.
The pathologies of full blown QFT seem irrelevant to understanding the issue of virtual excitations.
From Wikipedia: > Rudolf Haag postulated [1] that the interaction picture does not exist in an interacting, relativistic quantum field theory (QFT), something now commonly known as Haag's Theorem.
@DanielSank How do you "find" them in the inside? They are there in the perturbation series, but nature is not perturbative, the perturbation series is just our tool to compute something we're oto stupid to compute otherwise
@DanielSank Actually, you get into troubles as soon as you get infinitely many d.o.f., since the uniqueness of the representation of the commutation relations fails. I'm not sure how important the "relativistc" part is in this case
@DanielSank No, it's correct
Which is why I wish everyone stopped presenting virtual particles as if they were a fundamental aspect of QFT :)
@ACuriousMind Agreed, and I wish everyone would stop pretending they only show up in QFT!
I've made this comment several times before, actually:
There is an unfortunate tendency of this site to imply that many theoretical things (like moving poles around in the complex plane) are particular to QFT, and often even relativistic QFT.
@ACuriousMind Yeah, I mean it is just an intuitive representation of the theory, which of course is then interpreted maybe too accurately. BUT... so is the free particle. It just happends to be away from all of the interactions, or has minor interactions. And who knows how dressed even the electron is.
With a grain of salt, everything is a quasiparticle to me.
If it is easier to interpret as a single particle, I think it is no argument of it being any more real.
@DanielSank Yes, my point exactly. That even a free electron is a 'mess'. So why the free electron going in or out to the scattering even is more real, than something which happends in the middle. That notion of real is in this context just classical, I would say.
By the way, there is a nice quote about single particle picture from Pauli
Of your demands for a future [. . . ] field theory, the demand: “A single particle should appear as a trivialvsolution of the basic equations” (of which I know that it has been your favorite demand for months) seems rather questionable, since a charged particle is nothing trivial. (Pauli to Heisenberg, 16 July 1934)
Ok. I have reached that once then, while answering something trivial about gravity. It went to some hot questions list and ridiculous amounts of trafic came. That highlights the power of internet marketing, click-bait titles on newspapers etc. It is a bit unfair almost.
yeah, there are posts I am really kind of happy with that got like almost no attention, but well - they're not written for the rep after all and someone might still read them at some point if they need help/research something
I think it actually creates wrong incentives and is a bit broken, but yeah, I think the idea was to make people want to write good answers in order to get rep too
That is the true measurement problem. That my measuring things one defines their dynamics. Just like in quantum mechanics :D
For example, in democracy, the people who get elected are the people who are the best at getting votes. Same in Stack Exchange. This of course correlates with skill and effort to some extent, but there are other factors as well.
@SirCumference theres at least 1 cool documentary on supervolcanoes, there are something like ~50 around the world, and yellowstone has erupted a few times over millions of years with massive effect. another one to study is the toba eruption about 70K years ago & its now estimated to have a massive effect on homo sapiens, possibly/ almost driving to extinction.
@WilliamBulmer Secret found this new ref by Tenev, Horstemeyer, think highly relevant to your own inquiry (thx for sharing), think it can be built on/ expanded, hope you can stick around for further effort on that arxiv.org/abs/1603.07655
@DavidZ I'm not sure it's on topic, either. "Does a translation exist?" is fine, but "where can I buy it?" sounds more like what we were trying to avoid.
@0celo7 : It is not uncommon on MO for people to automatically downvote questions that have also been posted on MSE, especially if the poster appears not to have waited for a decent interval before reposting (e.g. four or five days) and doubly especially if the MO post fails to link to the MSE post.
@Decrypted $F=ma$ is Newton II in constant mass approximation; $E=mc^2$ is Relativity; squared velocity and acceleration have different units - I am not too sure what you want to tell us :| But yeah, they both scale linearly with mass ...
@Sanya All you need to do is bang off some answer that gets a good start on a question ends on the Hot Network Questions sidebar and let the throng take care of you.
It's a lot easier to cap since that thing came into being.
