# What is the origin of QFT "difficulties": "physical" or "mathematical"?

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Indeed, there is a 'currently" dominating "opinion" that relativistic QFT is "dictated" by this and that, so it is unavoidable that we encounter UV and IR difficulties. This and that are considered as ultimately established things amongst which there are Poincaré invariance, locality, etc., etc.

And in my opinion, there is still a room of improving the QFT initial states and interactions so that no UV and IR difficulties may appear. I propose you to express your opinion whether the current QFT is (are) satisfactory. Especially it concerns "gauge" interactions.

My question is motivated with mathematical approaches to QFTs like algebraic, axiomatic, etc. approaches. As to me, I think we have already sufficient experience in obtaining the final QFT results that may help us construct a theory without "difficulties".

asked Oct 14, 2017 in Chat
recategorized Oct 14, 2017

Poincare invariance is what defines relativistic physics in general, whether classical or quantum. It is not just an opinion but a demarcation criterion.

You prove nothing at all in the relativistic context since your toy theories don't respect Lorentz invariance. Whereas the consensus of the physicists (embodied in the standard model) is corroborated by a huge number of experiments.

Your main methodological error is that you dismiss the fact that the (Lorentz invariant) standard model passes almost all experimental tests with flying colors while your proposed alternative is nothing but a sketch of a hope, and doesn't accommodate Lorentz invariance, the most important requirement for a relativistic theory.

You also mistake the (free QFT) scaffolding for the (renormalized) final theory. It is like mistaking the power functions for the exponential function, since the latter can be defined as a power series.

The standard model is strongly coupled, due to renormalization and the summing of contributions from infinitely many Feynman diagrams, resulting, e.g., in poles in S-matrix elements indicating bound states. The latter are proof that strong coupling exists and is accounted for,.

That renormalizatrion is also used in the nonrelativistic case is irrelevant for relativity theory. What counts is that Lorentz covariance forces singular 2-point functions (a rigorous result) and hence requires to correctly work with distributions, including the splitting procedures that are the mathematical way of doing this singular renormalization correctly.

To get funding, you need to convince the funding agencies that your idea is more than pure speculation. Without showing how to account for Lorentz invariance, the chances for funding are essentially zero. There are too many dead ends to fund an idea that looks like failing on this account. And your proposal seems to be failing there.

The missing care consists of talking about big projects and proposals without first making sure that there is a basis for it. It is known for a long time that once one tries to get the Lorentz generators behave correctly, all problems show up that you are currently avoiding to tackle. They are not solvable by simply accounting for photon clouds but only by taking into account all what is already known, including the renormalization stuff.

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