Do aliens know about quantum fields? by Daniel Canarutto

Dear Daniel Canarutto,

My bet is with you, that the aliens would be very unlikely to have formulated quantum field theory. As you note, it is always risky to ask what is "real", but there is nothing in the physical record to suggest that a "quantum field" is anything more than an accounting device, for fitting theory to measurements.

Of course once one can generate anything with these imaginary fields, then you're off and running, and so Susskind and others propose literally hundreds of such fields to generate a multiverse, to avoid the problem of fine-tuning (because, he says, he does not like the implications of fine-tuning in only one universe!)

Your discussion of lack of real solutions, and the characteristics of "formal solutions" highlights the problem.

This is far too complex a topic to resolve in a comment, but I think Stephen Weinberg [p.49, Vol. 1] essentially supports your argument when he says:

"Quantum field theory is the way it is because (...) this is the only way to reconcile quantum mechanics with special relativity. (...) Quantum field theory is based on the same quantum mechanics that was invented by Schrödinger, Heisenberg, Pauli, Born, and others in 1925-26..."

In other words, it's a "fix".

Thank you for a fascinating essay covering the topic that in my view doesn't receive enough attention. I also invite you to read my current essay, and hope you will comment upon it.

My very best regards,

Edwin Eugene Klingman

Daniel -

I appreciate the clarity of your writing and thinking in this well-focused essay. I find it very plausible that the great success of QFT must be telling us some important things about the world, but we need a different set of fundamental concepts to express those things more clearly and simply.

Presumably one basic lesson is that what actually happens, in any experimental set-up, depends on an underlying web that includes all the possible modes of interaction. And I think your "somewhat alternative view" is also probably right - that the basic rules of physics can be expressed in simpler form if we think of this as a network of discrete correlation-events instead of a geometry inhabited by moving particles.

My own sense is that the key obstacle in fundamental physics is the assumption that it all has to come down to some one logically unified structure. The point of my essay is to suggest that such an interesting world as ours has to be built on a number of essentially different kinds of basic structure, such that each is meaningfully definable in terms of the others. That is, the rules may ultimately be simple, but they are also necessarily quite diverse, at least in any universe that makes all its parameters physically definable and measurable.

Thanks -- Conrad

Daniel,

Quite compelling ideas regarding the quantum world as we depict it. I especially like the question posed about scientifically advanced ETs not following the same path of quantum theory. Certainly the pitfalls of our mathematical modeling of the quantum world is suspect. I use the example of atomic orbital functions feeding into molecular orbital functions. How do you depict this quantum reality? We indeed do seem to view the quantum field as something physical. I have also noticed that we often attribute classical behavior to the quantum world in our quantum assumptions.

You beg a lot of questions that scientists need to answer.

Good job.

Jim

Dear Dr. Canarutto,

I read your paper several times. It is short and well to the point. Your observation about the quantum bundle is correct. The bundle ExM is constructed so that quantum fields on spatial surfaces are defined according to equal time commutators as spacetime Cauchy data. We have this whole Wightman construction for QFT, and it works pretty well. The problem is that for quantum gravity this clearly does not work. A black hole event horizon holds a quantum field as an "event" and this same field or an field entangled with it can exist in a region far removed. There is no direct meaning to coordinate geometry to quantum fields, but at best they have a representation in geometry.

Cheers LC

Dear Daniel,

You raise some interesting questions. It seems that you could have used some of the unused pages to flesh out your ideas about alternative formulations. I take it that you accept that any alternative formulation of QFT must be empirically equivalent, so your questions seems to me to boil down to the following: To what extent does the constraint of empirical equivalence constrain mathematical equivalence? At first, one might be tempted to say "completely", sort of like the Schrodinger and Heisenberg picture of QM (though I seem to have read a while ago somewhere some objections to this, but cannot remember the source). But it seems to me that your point is that the mathematical and physical difficulties you pointed out in your essays open up wriggle room for mathematically inequivalent theories, perhaps even completely unrecognizable to us, which are nonetheless empirically equivalent.

My own view is that it is likely that as time goes on, at least some of these difficulties will be overcome, and this may, depending on the solution, shrink or reshape the wriggle room. So, from my perspective, it is too soon to tell. Of course, if we ever encounter highly intelligent aliens, we would have a direct way of finding out:)

Best wishes,

Armin

Dear Daniel,

I read your essay with interest, however and despite all the things you point out, I would not agree with your conclusion : I think that scientifically evolved aliens would know about quantum fields. I mean that, while indeed the current formulations of quantum fields have problems and are not strictly, formally correct, they are nevertheless not arbitrary human constructs, but physically necessary concepts, if we take them not in a naive way but in their properly intended way. This intended way consists of an interplay between different formulations, and the different works we do to treat the divergences. So, even if each particular formulation, among those we have now, has troubles, we still give them indirect sense (which fits the "physical nature" of things) by our way of re-expressing things in other ways. So, what we truly mean by "quantum field" is not one particular formulation but the whole network of "equivalent" formulations we already have (even if all these formulations and our reasons to see them equivalent remain non-rigorous, until hopefully we will find a more rigorous solution). And I think these (non-rigorous) "equivalences" between formulations that we already manage to play with, precisely reflect their empirical equivalence (giving the same prediction), an equivalence class which is uniquely determined by, of course, experimental results.

In this sense, I do think scientifically evolved aliens would know about quantum fields, as there is only one such "equivalent class" of approximately mathematical theories that fits observations, which they should have found if they are successful at all in understanding particle physics.

Dear Daniel,

Very enjoyable and thought provoking essay! Your essay explores so compellingly the possibility of an alternative history of physics, which may have lead to something different than quantum field theory, whose problems you expose. Indeed, the problems start with the forced way of quantization, since we just generalized what we knew from the quantization of a point particle, to fields. This turns out to conflict with the gauge invariance and the representation of the potential as connection. Then, there is the problem of the artificial and ill-defined solutions, which arise as perturbative approximations but then are given absolute meanings. Then the renormalization techniques designed to fix the problems created by the approach itself, etc. I like the conclusion, "Perhaps transition probabilities, and other physically meaningful quantities, could be calculated starting from quite different principles and using partly different mathematics.".

I wish your essay will do well in the contest,

Cristi Stoica