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There are no particles, there are only fields (2012)
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- okket 10y agoSean M. Carrol always mentions this fact when he talks about QFT, which can be very entertaining like this one from 2013 "Particles, Fields and The Future of Physics" https://www.youtube.com/watch?v=gEKSpZPByD0 https://www.youtube.com/watch?v=gEKSpZPByD0 (Audio starts at 19 sec, Lecture starts at 2:00)
- IANAD 10y agoJust read this post from him recently, which, along with the referenced paper, was pretty enlightening: "Space Emerging from Quantum Mechanics" http://www.preposterousuniverse.com/blog/2016/07/18/space-emerging-from-quantum-mechanics/ http://www.preposterousuniverse.com/blog/2016/07/18/space-em... paper "Space from Hilbert Space: Recovering Geometry from Bulk Entanglement": https://arxiv.org/abs/1606.08444 https://arxiv.org/abs/1606.08444
- 2Pacalypse- 10y agoSean Carroll is very captivating and entertaining speaker. Thank you for the link.
- datihein 10y agoThis article did get published in the American Journal of Physics, and there was some back and forth discussion also published in the Journal. Unfortunately, the published version and the ensuing discussion is effectively inaccessible ... they want 30 USD from me to read each published response.
- S_Daedalus 10y agoIs any of it available on Sci-Hub, or be made to be available there?
- datihein 10y agoSources say: yes. But I found Art Hobson's website, which includes the published paper and the published commentary http://physics.uark.edu/hobson/publications.html http://physics.uark.edu/hobson/publications.html
- S_Daedalus 10y agoEven better, thanks for that link!
- monort 10y agohttp://physics.uark.edu/hobson/pubs/13.09.a.AJP.pdf http://physics.uark.edu/hobson/pubs/13.09.a.AJP.pdf
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- S_Daedalus 10y agoIt's either this, or something like objective collapse really does happen, physically, which seems less likely.
- kmm 10y agoI always enjoy a discussion about semantics, but only when both parties are very clear about the fact that it's semantics they're talking about, and not fundamental nature of existence. I'm very wary of people trying to use physics to further an ontology, as physics almost by definition allows for multiple, completely equivalent descriptions of reality. That's not to say I think physics teaches us nothing about how the universe really works, but I don't think you can conclude from his interpretation of the mathematics of QFT that particles (whatever they are) don't exist, just as much as the Fermat principle[0] doesn't imply that light has a sentient mind which seeks out the shortest path. There exists a consistent, fully equivalent interpretation of (non-relativistic or relativistic) quantum mechanics that includes particles at the core of its ontology, Bohmian mechanics[1]. I'm personally not an adherent of it, but it shows that by nature, it's very hard to use physics to show what something fundamentally is. Besides, the article doesn't define clearly what it means by particle, which is a priori just an English word, nor does it justify it well. I don't share the authors' problem with the excitations of a field being spread out all over the universe (by virtue of them being momentum-eigenstates). It's discrete, has a mass, has a momentum, and energy and interacts as a whole. The article calls these properties necessary but not sufficient, but doesn't explain why this doesn't suffice. Particles are at least a useful abstraction. They emerge naturally at the classical level, interactions between fields are even at extremely high energy levels still very localised, electrons "scatter" a lot like they're bouncing off other particles, they leave neat tracks in bubble chambers, excitations of fields are discrete even at the lowest level, ... Feynman diagrams[2] are extremely handy, even if they don't "actually" happen, but are just a term in the series expansion of an interaction Hamiltonian between two fields. What's the use of contorting oneself to the limit to fit every observation in a single mold, a field. Sure, classical particles are nothing like what we see at the quantum level, but classical fields are absolutely nothing like the fields in quantum field theory either. Why pick one term over the other? 0: https://en.wikipedia.org/wiki/Fermat%27s_principle https://en.wikipedia.org/wiki/Fermat%27s_principle 1: https://en.wikipedia.org/wiki/De_Broglie%E2%80%93Bohm_theory https://en.wikipedia.org/wiki/De_Broglie%E2%80%93Bohm_theory 2: https://upload.wikimedia.org/wikipedia/en/f/fb/Feynman-diagram-ee-scattering.png https://upload.wikimedia.org/wikipedia/en/f/fb/Feynman-diagr...
- TheOtherHobbes 10y ago
- ScottBurson 10y agoInteresting that the paper starts by attacking "quantum mysticism". Seems to me that the argument it's making renders quantum mysticism easier to believe rather than harder. The concept of particles, after all, appeals to our Newtonian "billiard ball" intuitions; particles are the essence of locality, and our intuitions suggest that a particle universe should be deterministic. On the other hand, if particles are epiphenomenal, and everything is really infinite fields which only have a certain probability of interacting in certain ways, it seems like, intuitively, there's a lot more room for consciousness to influence those fields in a nonlocal manner. No? Just playing devil's advocate here :-)
- Houshalter 10y agoNot at all. Fields are a precise mathematical model that could, in principle, be simulated on a computer to arbitrary precision. There's no room for mysticism or "consciousness" nonsense.
- crististm 10y ago<ironic> right... and you also can simulate initial conditions to infinitely arbitrary precision as well.
- andrewflnr 10y agoin principle You're missing the point, which is no room for mysticism or "consciousness" nonsense not anything to do with the limits of computation.
- pg_is_a_butt 10y agoyou're missing the point, which is you're all idiots.
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- Animats 10y agoThere is only the mathematics. "Shut up and calculate", as one physicist put it. Here's Feynman talking about it.[1] "We interpret the intensity of the wave as the probability of finding a photon". [1] https://www.youtube.com/watch?v=_7OEzyEfzgg https://www.youtube.com/watch?v=_7OEzyEfzgg
- daxfohl 10y agoI feel this approach is flawed. In theory it'd have been possible to come up with Relativity by recognizing the Lagrangian transforms that match experimental outcomes and say "That's just how it is". Einstein provided an insight as to why that's far more enlightening. To me, QM is still in the former state, detailed equations looking for a soul.
- andrewflnr 10y agoThat was eye-opening, and not just with regard to the titular subject. I'd never thought of energy stored in fields as a consequence of energy conservation.
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- atemerev 10y agoAnd in another 100 years or so, this will finally make it to textbooks... Quantum field theory is weird, but there are much more compelling analogies in classical world than particles. (Feynman was a fan of particles, but I presume he was aware of the problems with this representation). When you speak of fields and wave packets, you eliminate the uncertainty principle, and double-slit experiment is no longer a paradox — no small feat to achieve.
- andrewflnr 10y agoWhat do you mean about the uncertainty principle? The article here still relies on it.
- tim333 10y agoI think he means if you model things as waves the uncertainty comes about naturally. For example if you send a wave through a small hole so you know it's position accurately on two axes then that causes it to diffract out so you don't know it's direction/velocity along those axes. (sort of illustrated: http://physics.stackexchange.com/a/61475 http://physics.stackexchange.com/a/61475)
- dnautics 10y agoIt reduces to the standard Fourier uncertainty: if you have an energy packet (gaussian e.g.) of a certain width and wavelength, the shorter the width, the more uncertain your wavelength will be.
- scotty79 10y agoThat's how I feel about quantum physics. Just fuzzy waves interacting randomly with each other, exchanging some quantities and reshaping, sharpening or blurring each other. The fact that some of the energy and momentum exchange are governed by similar rules as two billiard balls bouncing from each other is pure coincidence (or just effect of the fact that round macroscopic objects behave like very sharp quantum waves).
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- sbussard 10y agoAnyone who's studied beginning grad level physics should know that. I don't get why it's trending on HN
- gunnihinn 10y agoPerhaps for those few of us who are a bit rusty on beginning grad level physics.
- GolDDranks 10y agoMost of us haven't studied grad level physics?
- sbussard 10y agoIt's presented as if it's a new discovery. If someone's interested in Physics, they should study Physics. It doesn't help much for one to jump right in the middle of a subject and act like they know what they're talking about. Which is exactly what linking to this scientific paper on HN encourages. In this case, anyone who could understand the paper would very likely have encountered the information already. I've seen too many programmers act as if there's nothing they don't know or can't understand after a weekend's worth of study. That kind of arrogance is what separates scientists from pragmatists. It leads to situations like this: http://academia.stackexchange.com/questions/9602/rediscovery-of-calculus-in-1994-what-should-have-happened-to-that-paper http://academia.stackexchange.com/questions/9602/rediscovery...
- joeberon 10y agoYeah I'm being taught QFT in my undergrad. Any theoretical physicist would be expected to know this concept well. I guess people here aren't theoretical physicists though! However I do think the quality of physics commentary here is generally quite poor. I see a lot of crackpot theories or just ignorance in general. Especially with anything involving quantum mechanics, that seems to drive people crazy. I don't think that many people realise that in physics we don't talk about the philosophical implications at all, we're just trying to find good models, that's it...
- platz 10y agoas water waves are 'epiphenomena'/emergent from the underlying form, are the 'waves' that are used to describe light also epiphenomena (i.e. emergent) or are light waves the EM field exactly ? If the latter, I don't see how to interpret the photoelectric effect.
- Retra 10y agoAll phenomena are emergent. That word means nothing. The photoelectric effect is not complicated any way you slice it. An atom absorbs some quantum of energy from the field. This doesn't require any understanding of what model you use to describe the energy in the field. The interaction is quantized either way.
- platz 10y agonot quite. 'emergent' in theoretical physics typically means 'arising from a composition of the more fundamental physical state'. 'All phenomena are emergent' with this definition of the word would mean you could always represent something with something else that is more basic, ad infinitum - I don't think that is the accepted view among physicists.
- Retra 10y agoI'm not sure the term "emergent" is a term in theoretical physics. I've certainly never seen it. >'All phenomena are emergent' with this definition of the word would mean you could always represent something with something else that is more basic, ad infinitum No, what it means is that at some point, you've broken your model down into something that is not 'phenomena' in any meaningful sense. Which is something physicists do all the time.
- fu9ar 10y agothe map is not the territory. the model is not Absolute, but it gives us a really, really good idea.
- Ono-Sendai 10y agoGenerally I think the field idea is more plausible than the particle idea. But I think there are some things that the field can't explain yet (to my satisfaction at least). Why, whenever we measure the charge of an electron, do we measure the same value? Why not one half, or one third of that charge sometimes? After all, if an electron is just a disturbance in a field, why might we not capture just part of that field in our measuring apparatus? This is of course trivially explained by the particle idea.
- blueprint 10y agoIn fluids, we sometimes get discrete but dynamic structures. Those structures would not be stable without a certain base energy. That could explain it. For example, suppose an electron is a vortex.
- Ono-Sendai 10y agoI have seem some papers discussing the idea of an electron as a ring or vortex of electromagnetic energy. I believe the idea is still purely speculative though.
- blueprint 10y agoIt can be said to be speculative, but if the model can explain everything in the world of phenomena, including things that are not explained by particle physics, then, by the same token, so can particle physics. What we need is for the theory to be put to paper and then simply confirmed by a lot of people. Then people will start to develop new technology with the things that it can explain and by that point no one would say it's not confirmed. But I have found that there are societal and psychological issues which prevent many people's confirmation of the basis of my supposition.
- snovv_crash 10y agoThat actually makes a lot of sense to me. What with E=MC^2, antimatter explosions, generating new particles from collisions, everything.
- rrggrr 10y agoCan someone ELI5 or possibly 15 on this for me?
- Gnarl 10y agoNothing new. This guy published a book about it in 2006: http://transfinitemind.com/tapestryindex.php http://transfinitemind.com/tapestryindex.php
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- dmfdmf 10y agoPlatonism and Kantianism are still alive and strong in Western thought.
- gpsx 10y agoFrom the paper, at the top of page 10 of the PDF, at the end of section A: "Some authors conclude, incorrectly, that the countability of quanta implies a particle interpretation of the quantized system. Discreteness is a necessary but not sufficient condition for particles. Quanta are countable, but they are spatially extended and certainly not particles. Eq. (3) implies that a single mode's spatial dependence is sinusoidal and fills all space, so that adding a monochromatic quantum to a field uniformly increases the entire field's energy (uniformly distributed throughout all space!) by hf. This is nothing like adding a particle. Quanta that are superpositions of different frequencies can be more spatially bunched and in this sense more localized, but they are always of infinite extent. So it's hard to see how photons could be particles." As mentioned above, you can take linear combinations of these different single particle states at different energies and come up with various energy/location spreads. Doesn't one such combination have a spatial spread of zero? This would correspond to a single quanta at a single location in space. My physics may be a bit rusty since I have been out for a while. Combining the different frequency components from the different field configurations is not _exactly_ the same as simple Fourier analysis, on the face of it. However, the individual contribution from a given field configuration (meaning a single frequency) is very small since there are so many different field configurations contributing (an infinite number). I believe the Fourier result does apply to the expectation value of the particles location here. If I am thinking correctly this seems to be a very critical error in the paper. Someone correct me if I am wrong. * * * EDIT: I believe I said something incorrectly. Where I said "I believe the Fourier result does apply to the expectation value of the particle's location here." I meant to make a stronger statement, "I believe the Fourier result does apply to the effective value of the particles wave function in this location in this case." (The expectation value being zero would not bean the field does not extend to that location.)
- sova 10y agoI suppose the whole crux and beauty of the article is that we can talk about physics without numbers. As soon as numbers enter the picture, we have discretized something that is beyond discretization.
- rrmm 10y ago(Not a physics person, but) As I read it, he is just arguing against the implication that Countability implies Particles. So he is saying that adding a quantum that is monochromatic has an effect across all space (which is clearly a non-particle like effect). Then he admits that you can get localization through superpositions of quanta. Since he is arguing against a logical implication he only needs to show a counterexample exists. The problematic part in choosing a single mode like this is that it can lead to a non-normalizable integral at some point (ie, it won't be a member of the Hilbert space). QFT always made more since to me. Everything flows more naturally than in QM, where out of the blue, they introduce wave packets. The paper does feel a bit shaky though especially as it is essentially taking a pedagogical point (start teaching from a QFT viewpoint) and making it into an argument about the foundations of physics. The non-relativistic QM view point is taught because it represents a smooth departure point from classical thinking without requiring the full mathematical complexity of field theory.
- WhitneyLand 10y agoHere another physicist challenges Hobson for not respecting realism, and he has a pretty good come back: http://physics.uark.edu/hobson/pubs/13.09.a.AJP.pdf http://physics.uark.edu/hobson/pubs/13.09.a.AJP.pdf
- kkylin 10y agoThe abstract already lost me: "Thus the Schroedinger field is a space-filling physical field whose value at any spatial point is the probability amplitude for an interaction to occur at that point." But the wave function lives on the configuration space of the system: if you have $N$ particles, the wave function lives on $R^{3N}$. In what way is this a "space-filling physical field"? Admittedly I haven't had time to do more than skim the article; perhaps it's explained more carefully later on. (Off-topic, but since this has come up a number of times on HN: this point is also where Bohmian pilot wave theory has never been wholly satisfying for me. If you accept the pilot wave picture, then the double slit loses a little bit of its mystery, but many-body theory still seems just as weird as before.)
- zeroer 10y agoIf there are no particles, then how do you know what $N$ should be?
- dschiptsov 10y agoParticles is just result of [self-centric] human perception bias and the resulting naive concept of matter or a substance as perceptual conditioning, evolved in a certain physical environment (everything what we are, including our mind and consciousness is shaped by the environment, and our perception of reality, in turn, is shaped by our mind, conditioned by perception). We think that there are solids and atoms - grains of matter - basic building blocks. This model corresponds to what our sense organs give us. It is hard to convince oneself that there is no matter at all, only energy and our perception grossly zoomed out of what is really going on. Matter is an appearance to perception. A wrong model due to limitation of the sensory system. There is no matter when there is no observer, only states of energy, or fields, which is a better concept, but still mere concept. We could say that atoms are "stable" fields, but it is much better to do not apply "human" predicates to the nature. Particles is a good-enough model, which allowed us to sequence a genome or build a CPU, but it is only a crude model nevertheless.
- ptrincr 10y agoThis only clicked for me a few weeks ago, but it finally gave me an understanding of the Higgs field, and the Higgs-boson. So the Higgs field is everywhere, like the electron field and the electromagnetic field (all elementary particles are thought to have their own field, as I understand it). As excitations of one field (electrons etc) interact with the Higgs field, they experiance a kind of drag and this interaction gives them mass. So how about this Higgs-Boson then? Well if you produce enough energy, like smashing two protons together at huge speeds, this energy is released and some of it ends up in the higgs field, producing an excitation of the field, which we detect as the Higgs Boson. It's unstable and quickly releases it's energy which dissipates into other fields, producing more excitations which we see as more particles. Before I understood this, I was trying to work out how if the Higgs-Boson was responsible for mass, why it needed so much energy for it to appear. All makes sense when you think about it as a field.
- blablabla123 10y agoThe professor I wrote my diploma thesis at said to me: quantum fields and the corresponding operators are just mathematical crutches because that stuff can't be described otherwise.
- bitkrieg 10y agoIf anyone is interested in the mechanics of the higgs field / basic quantum mechanics in general, I found this lecture to be an excellent explanation: https://www.youtube.com/watch?v=JqNg819PiZY https://www.youtube.com/watch?v=JqNg819PiZY
- johndoe4589 10y agois this essentially a reminder that the materialistic view of the universe / reality is outdated, or am I reading too much into it?
- nobrains 10y agoThe day I understood this, it was a awe moment. The realization that if we zoom in very very deep, we will not see marble-like particles, rather we will see nothing. Its only through the interaction of the excitation in these fields do our pseudo-particles form.
- virtualritz 10y ago"Physicists are still unable to reach consensus on the principles or meaning of science's most fundamental and accurate theory, namely quantum physics. An embarrassment of enigmas abounds concerning wave-particle duality, measurement, nonlocality, superpositions, uncertainty, and the meaning of quantum states. After over a century of quantum history, this is scandalous." What is also scandalous that in this age of systems that do this work for you automagically (e.g. Tex) typesetting and microtypography in scientific publications seem to deteriorate. This one is a fine example of this trend. ;-)
- snarfy 10y agoI never understood why interpretations of QM which violate non-locality like pilot wave theory are frowned upon. Fields are non-local by definition.
- amai 10y agoThere are followup comments to this paper: * http://physics.uark.edu/hobson/pubs/13.09.a.AJP.pdf http://physics.uark.edu/hobson/pubs/13.09.a.AJP.pdf * http://physics.uark.edu/hobson/pubs/13.09.b.AJP.pdf http://physics.uark.edu/hobson/pubs/13.09.b.AJP.pdf
- erdevs 10y agoTotal aside and this may be too late into a crowded thread for anyone to notice this. But have physicists ever rigorously examined the idea that quantum "duality" is explained by computational complexity? I know it's more metaphysics/interpretation, but that's what we're talking about here. I also know that universe-as-simulation is a very popular notion among laypeople (particularly programmers) who look at physics. I'm just wondering if any physicists have rigorously studied the idea, and if there are falsifiable propositions we could make about this. In game programming, one often cannot compute every detail of every component of a simulation. So, what you often do is focus more precise computation on areas around a player, or what the player is actually observing. The rest are often modeled stochastically or via computationally efficient functions. This has always mapped well in my (very surface-level, entirely layman) understanding of QM and QFT. Note that there are, in my mind at least, two different notions here. One is actually the concept of a simulation with observer-dependencies directing the fidelity of the simulation. The other doesn't imply a "simulation" nor is it directly dependent on any "observer": perhaps computational complexity is related to the fundamental physics of the universe and nature prefers to use imprecise probability estimates wherever possible and it is only when precise interactions need to be resolved that more precise or definite calculations are performed. I know these are sloppy notions as presented here and I'm not taking the time to phrase these questions very well, or very precisely. Busy atm, sadly. Just wondering if any well-reputed physicists have studied this possibility rigorously, or if it has been rejected for an obvious reason, etc.
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