The Case for Strong Emergence by Sabine Hossenfelder

Dear Sabine,

I enjoyed reading your essay. The essential part of your contribution seems to be the middle part of p. 9, so it is on this part that I want to comment. It is curious to note that the type of loophole you notice here is of a similar kind as one that has been discussed previously in the context of non-Lipschitz classical mechanics. To be clear, I don't want to suggest that your observation isn't novel, but merely to draw attention to an analogous historical case, which you or other readers of this forum might find interesting.

It was observed, by Poisson and others, that for certain forces and initial conditions, the Newtonian equation of motion has multiple solutions. This was discussed in the 19th century as a possible loophole for reconciling classical mechanics with human free will. The debate has been described very clearly in a paper by van Strien: "Vital Instability: Life and Free Will in Physics and Physiology, 1860-1880".

The analogy I notice between the 19th century singular points in mechanical problems that lack Lipschitz continuity and your "non-divergent function that can't be continued" is based on two elements. (1) They are both closely tailored to the mathematical framework at hand. (2) Neither is restricted by probabilities governing the multiple solutions. So, the usual argument for strong incompatibilism, which says that free will is not compatible with determinism nor with fixed probabilities or randomness, doesn't seem to apply.

Best wishes,

Sylvia

Dear Dr. Hossenfelder,

thank you for this essay, which I found interesting indeed.

In particular I liked that you point out that although reductionism ddoes work, or actually did work, it ain't necessarily so (if yo have the occasion to read my essay as well, you will find some common points about this).

Also, I totally agree on your definition of "physical theory" that encapsulates both the formalism AND the operational laws that connect the symbols to the observables. A concept that is not clear even among many professional theoreticians.

However, I found a bit misleading your definition of fundamental (even if you maintain: "This definition I think captures how the word is used in the foundations of physics today" and not your own thought). In fact, what you propose here is a different form of reductionism, known as "theoretical reductionsm" (whereas when you refer to reductionism it seems you refer to the so-called "ontological reductionism"). IN general throughout your whole essay I think is not always clear the ontological status of your statemens. It seems that sometimes you refer interchangeably between the supposed "true state of affair" (e.g. when you say that bigger things are made of smaller thing) and theoretical abstractions (like in your notion of fundamentality and emergence).

Despite this, I enjoyed reading the essay and I will rate it high

I wish you success,

Flavio

Dear Sabine,

it was a pleasure to read your essay. You propose an original, interesting idea and your writing style is very enjoyable - it's definitively between the best I've read here so far.

I've a question about your strong emergence hypothesis, since I've not the mathematical tools to judge your example at §6 (my formation is as a philosopher).

Are the phenomenal, subjective sensations (i.e, how the color "red" looks like) a possible example of strong emergence (like the theory 9 in your fig.2)? It's the old stuff of the hard problem of consciousness: we can describe sensations with many good theories, but none will successfully explain "how/why they feel", that seems an irreducible trait.

Or maybe they are just irreducible systems? If I express "red" in terms of electromagnetism, I am not talking about the sensation of the colour red, while if I express the sensation of the colour red, (for example through metaphors, synesthesia, neuronal stimulations, memories or fantasies) I am not explaining its electromagnetic qualities.

Best regards,

Francesco D'Isa

Great essay! What you point out is what happens at a singularity in RG flow, and the inability to continue beyond it means the solution on the other half could be something entirely different.

I have pondered the idea the Landau in gravity and QCD. Suppose SU(3) is really a reduction on SU(4) which as an STU type duality with SU(2,2). This is the isometry group of the AdS_5 and this set up is a form of gauge-gravity duality

Given a group G and a subgroup of it K to which it is spontaneously broken, the broken generators ("axials" in the chiral symmetry breaking paradigm of low energy QCD, SU(2)Ã--SU(2)/SU(2)_isospin is the coset space H=G/K. The generators of G than break up into the unbroken ones, k, (isospin), and the broken ones, hh, parameterized by the goldstone/pions serving as projective coordinates of that manifold (In QCD this is just S_3):

[h, h] ⊂ k,[h, k] ⊂ h,[k, k] ⊂ k.

The unbroken generators (isospin) close to a subalgebra, and the broken ones (axials) transform by the k as isomultiplets. In this way in the IR limit QCD recovers the isospin theory of nucleons.

So the idea would be that gravitation has a dual RG flow that hits a pole at the Planck or string scale. This would then lead to the emergence of new QFT-like physics or maybe forms of partons associated with gravitation. This might be one way the singular problems could be managed; we transform conformal gravity into a form of QCD where the IR limit there corresponds to the UV limit in gravity.

BTW I like you blog, though I have never commented there. I have been more of a lurker. If you have time you might be interested in my essay.

Cheers LC

Hi Sabine,

thank you for your kind reply.

I've another doubt: you say that is should be a same-level problem because I was trying to disentangle the sensory response (this is red) from the knowledge of it (I see red).

But aren't they already disentangled? Electrodynamics and atomic physics doesn't need any qualia to work and to give their explanation of the relation between colors and (human) observers. For sure qualia and physics are related (no brain, no mind), but the first are entities that physics doesn't need - and if we agree that they exists, they looks like an emergent propriety.

Moreover, just out of curiosity, there are other examples of strong emergence that you can imagine, a part of the one of §6?

(Anyway, maybe I've misunderstood, I know that my limits in front of the core of your argument are a serious obstacle).

Best,

Francesco

Hi Bee,

This is an idea I have been kicking around in my mind. It seems to fit with the idea of strong emergence. If this happens with QCD in the IR limit, which is a bit of a problem, then by STU type of duality with gravity it might carry over to quantum gravity.

It could happen either within string/M-theory or with the constructions from the WDW equation such as LQG. I am not picky. I figure either if LQG is false this might form some sort of constraint in string theory that rules out some set of states, or if LQG is true then again it might form such a constraint or provide tools to show how some set of solutions there are not physical.

At any rate it could in the end be false. You have to propose in order for something to be disposed.

Cheers LC

Hi Sabine,

Your expository skills have made the essay quite enjoyable to read. You have illustrated your points very well, and your definitions are extremely astute.

You have also been very prescient in mentioning the Halting problem, which is certainly quite relevant to your article. My first thought when I read your definitions was of the issues brought up by the Halting problem.

In fact, I did not quite understand how you eliminated said issues in the context of weak emergence. It seems to me that it would follow from the Problem that one can never be certain about whether or not a theory B can be derived from A. How do you propose to eliminate this blip?

My own ideas are surprisingly similar to yours on theories and reductionism. However, I chose to take a different path in order to avoid this seemingly insurmountable issue. I think you would quite like the parallels made!

Regards,

Aditya

Sabine,

I enjoyed your thorough examination of the cogs and wheels of what makes fundamental theories. But, in my opinion, you started on the upper floor, way above the fundamental part of the universe. What is fundamental is what the universe is and does before we look or even think about it. All the rest is knowledge which is not a dimension of the universe.

The fundamental is what makes up the universe (substance) and what is behind its spontaneous evolution (cause). Alas, FQXI is drumming up the science/physics aspect that we create by perception (senses - mind) and denies the right of the universe to exist and happen on its own outside the scope of our experience. We are not missing much, but that little part that is what exists when we are not around... is fundamental. From it, we may build real emergence.

All the bests,

Marcel,

Sabine,

"A physical theory is strongly emergent if it is fundamental, but there exists at least one other fundamental theory at higher resolution."

I am puzzled by something. Why isn't GR considered to be strongly emergent? Doesn't it play the role of theory 9 in your figures? What am I missing in your definition? Is GR not fundamental?

BTW, this is a very good essay and easy to read. I was able to follow the text easily despite having no special education in Physics.

Also, allow me to thank you for your website. I have lurked there quite a bit. I find your explanations to be very helpful.

Best Regards and Good Luck,

Gary Simpson

Dear Sabine,

Nothing is basically wrong with reductionism and free will, provided we take to heart some provisions. I think all science begins with natural language (L), because he who does not know what distances, stones, rivers, weights, birds, stars, colors, seasons, etc. are cannot be a scientist. Scientists are people making claims (construct theories) beyond L, e.g. about H2O. In order not to remain castles in the air their theories must be grounded somewhere and the only place to ground them is in L. But L (to stay in the picture) is ignorant of atomic bonds, valences, molecular weights, joint electron orbits, etc. Great! Something has been ADDED to L Absolutely not contained in it - hence it cannot possibly be false. The problem begins only - as unfortunately is the rule - when scientists elevate H2O over L (known as epistemological inversion). What, however, shares no common measure can neither be represented by one of its parts nor can they be equated.

Et voilà! The problem of free will vanishes, because it is no point physics has anything to say about.

Heinrich

It is an interesting essay, and a good essay.

I am thinking, reading your essay, that if there are two fundamental theory, what is the most fundamental? If the results are the same, and there is a complete equivalence like the matrix mechanics and the Schrodinger wave formulation, then it could be the simplicity in use (the mathematical description and the calculations) that sorting the theories.

I am thinking that all the theories that have infinitesimal variation of the free parameters, or using additional infinitesimal terms, could be fundamental because of they are all equivalent in the experimental observations (with sufficiently small variations): the additional parameters are infinite, and the theories are infinite.

Regards

Domenico

Dear Dr Sabine Hossenfelder,

Reliable evidence exists that proves that the surface of the earth was formed millions of years before man and his utterly complex finite informational systems ever appeared on that surface. It logically follows that Nature must have permanently devised the only single physical construct of earth allowable.

Joe Fisher, Realist

Dear Sabine,

I am happy that you still decided to particpate.

Your approach of "weak emergent" and "strong emergent" is refreshing so is the "resolution" of experiments and theories and useful for my own thinking.

Reductionist elementary particles do NOT influence your behaviour is a perception that I can underwrite a good example to underwrite this perception is the essay from Erik P. Hoel from last year about "Causal Emergence" link.

You are right when you say that many physicists don't accept strong emergence because it is incompatible with their ideas. I think mankind need an open mind and even has to accept to say "I don't know" (if you can then you start thinking and searching...)

"Stuff is made of smaller stuff". Indeed but it is possible to start at the bottom then we can conclude that this ultimate bottom is unknown, it is no longer "stuff". so Unknown-Quarks-Atoms-Chemicals-Cells-Organs-Agents. At each step there is a larger choice of possibilities. Each step is a threshold where new entities are emerging.

A correct candidate for a fundamental theory might not reveal itself at "first sight". That is the problem with science. It is like we thought for a long time that the sun turned around the earth, difficult mathematical structures were found to prove it because at first sight it "seemed" as if. Maybe the same for theoretical science in our era.....

Your example of the Chief of CERN is a nice one. My perception is that the agent (chief) is at a specific MOMENT in time where the whole block universe that he is part of (his emergent reality) takes his decision. At that very moment ALL emergent phenomena (including the bottom ones) are simultaneous "existing" and interacting.

(so all are shaking hands).

I am very happy with your conclusion Sabine, because it means that we can think FREE. I hope that you will find time to read and rate my essay where I am also trying to find a strong emergent model.

Best regards and good luck

Wilhelmus

Sabine,

Nicely argued. But do you feel a little like an accountant shuffling last years books into order while there's no CEO to advance the company? You may agree that many times in the past physicists have said "It's all sorted bar a bit of tidying up". Doesn't p.1 repeat that? Sure we need accountants but who if not you steers the ship (and where if not here) into the vast unknowns? Thanks for the free will, but I worry! Hasn't getting to locked into current theory always been the bane of advancing understanding?

So; "A physical theory is fundamental (without qualifier) if it is to best current knowledge". But we know most all are flawed or incomplete at best! Do you really assert we must settle for that as 'What is fundamental' in the universe? Who is who should then search the data and logic for that common solution to the hundreds of fundamental problems, anomalous findings & paradoxes? (and that's just in my own field!) Or, most importantly, who at very least glances at the work of those who do? certainly not fearful editors!

You argue well in your chosen domain, but if we need to advance understanding do you really believe that's that not really just a sideshow? ...Yes, I felt a bit disappointed, and worried. Can you convince me I shouldn't be?

But I have hope!! ..I hope you'll give your view (breaking stony silence) on large scale physical modelling of detection in QM, seeming to yield a classical solution (see also Declan Trail's essay for the code and plot).

Nicely written Sabine. I love your style and you met the scoring criteria well, but was it truly fundamental? Hmmm.

Very best.

Peter

Sabine,

What is will supposed to be free of? Don't most people, willfully and consciously, use their powers of concentration, from prayer in church, to learning in school, to re-enforce, extend and strengthen their prior beliefs and assumptions?

Now if you were to argue our actions are pre-determined, by deterministic laws of nature, then you would be wrong. While effect is determined by cause, the input into any event is only calculated by its occurrence. Time is not a set dimension along which we deterministically travel from past to future, but change turning future to past. As in tomorrow becomes yesterday because the earth turns.

Time is an effect, similar to temperature. We only naively equate it with space because our thought process functions as flashes of cognition, so we think of it as linear sequence.

Events have to occur, in order to be determined. The past is an effect of the present. As Alan Watts pointed out, the boat creates the wake. The wake doesn't steer the boat.

Time is asymmetric because action is inertial. The earth turns one direction, not both.

Different clocks can run at different rates because they are separate actions. A faster clock will use energy quicker, like an animal with faster metabolism will age quicker than one with a slower rate.