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Point particles RIP

I typically add samples of books to my Kindle library when considering purchases. While examining my Kindle library yesterday, I started reading a sample of Art Hobson’s 2017 book Tales of the Quantum: Understanding Physics’ Most Fundamental Theory and then became interested in his background. A Google search found biographical information, references to his books, YouTube videos, and his 2013 paper “There are no particles, there are only fields.” 1

Well, that paper was useful, because it says what I might say if I had the proper physics “chops.”

To find out what textbooks say, I perused the 36 textbooks in my university’s library having the words “quantum mechanics” in their title and published after 1989. 30 implied a universe made of particles that sometimes act like fields, 6 implied the fundamental constituents behaved sometimes like particles and sometimes like fields, and none viewed the universe as made of fields that sometimes appear to be particles. Yet the leading quantum field theorists argue explicitly for the latter view (Refs. 10-18). Something’s amiss here.

In physics lab at Caltech in the early years of the “red book” The Feynman Lectures on Physics class, we did the double-slit experiment (not the “dim” beam version, as I recall). That experience left me dissatisfied. My takeaway was “okay, light acts as both a particle and a wave — what’s next?” My gut feel over the years was that the photons (or electrons in a similar experiment) interacted with the slits. But the duality was left hanging — nothing beyond paradox.2

In this chapter we shall tackle immediately the basic element of the mysterious behavior in its most strange form. We choose to examine a phenomenon which is impossible, absolutely impossible, to explain in any classical way, and which has in it the heart of quantum mechanics. In reality, it contains the only mystery. We cannot make the mystery go away by “explaining” how it works. We will just tell you how it works. In telling you how it works we will have told you about the basic peculiarities of all quantum mechanics. — The Feynman Lectures on Physics, vol III, p. 1-1 (1965).

So, here the Quantum Field Theory (QFT) context offers some closure. A career physicist (Hobson) explains something that I’d not encountered so clearly in my reading the last few years.

In the 2-slit experiment, for example, the quantized field for each electron or photon comes simultaneously through both slits, spreads over the entire interference pattern, and collapses non-locally, upon interacting with the screen, into a small (but still spread out) region of the detecting screen.

Lately while reviewing the saga of infinities in modern physics and continuing to ponder how to visualize a classical Coulomb field for an electron using a QFT framework (with virtual particle screening, photon exchange in Feynman diagrams, vector potential field, etc.), I was really frustrated with the notion of point particles. 🐟

Perhaps we can say “point particles RIP,” eh (especially oscillating ones).4

For example, now we can explore how energy is “bundled” into discrete quanta (Feynman’s wiggles or excitations of spatially unbounded continuous fields), and how an electron — as a unified bundle of field which hits like a particle — interacts with other field bundles, universal fields, and the vacuum.

Hobson notes:

“How can any physicist look at radio or microwave antennas and believe they were meant to capture particles?”31 It’s implausible that EM signals transmit from antenna to antenna by emitting and absorbing particles; how do antennas “launch” or “catch” particles? In fact, how do signals transmit?

The superposition principle should have been a dead giveaway: A sum of quantum states is a quantum state. Such superposition is characteristic of all linear wave theories and at odds with the generally non-linear nature of Newtonian particle physics.

A benefit of QFTs is that quanta of a given field must be identical because they are all excitations of the same field, somewhat as two ripples on the same pond are in many ways identical. Because a single field explains the existence and nature of gazillions of quanta, QFTs represent an enormous unification. The universal electron-positron field, for example, explains the existence and nature of all electrons and all positrons.

… Einstein’s goal of explaining all fields entirely in terms of zero-rest-mass fields such as the gravitational field has not yet been achieved, although the QFT of the strong force comes close to this goal of “mass without mass.”

And I started my physics blog for the same reason Hobson notes in the preface to his book, namely, as someone “who would like to better fathom, before they depart this mortal coil, what makes the universe tick.” 3

 

[1] Submitted 2012; published March 2013. https://arxiv.org/abs/1204.4616 (https://arxiv.org/pdf/1204.4616.pdf).

[2] As Feynman said, “It is what makes physics fascinating.” — The Feynman Lectures on Physics, vol III, p. 18-9 (1965).

In his paper, Hobson notes:

For Richard Feynman, this paradox was unavoidable. Feynman was a particles guy. As Frank Wilczek puts it, “uniquely (so far as I know) among physicists of high stature, Feynman hoped to remove field-particle dualism by getting rid of the fields” (Ref. 16).

I encountered this characterization of Feynman as a particles guy at least once before. But currently I cannot find such a citation in my notes. So, I cannot say whether others besides Wilczek held that opinion. Wilczek’s original 1999 article “The persistence of ether” is archived here.

And Hobson further goes on to quote from Feynman’s introduction to one of his lectures (The Character of Physical Law, The MIT Press, Cambridge, MA, 1965) where he says:

I am going to tell you what nature behaves like. … Do not keep saying to yourself, … “But how can it be like that?” because you will get “down the drain,” into a blind alley from which nobody has yet escaped. Nobody knows how it can be like that.

One may consider the tone of Feynman’s discussion of wave-particle duality by reading from The Feynman Lectures on Physics online — from Volume 3, Chapters 1 and 2 (the same lectures in Chapters 37 and 38 of Volume 1): Quantum Behavior and The Relation of Wave and Particle Viewpoints.

[3] Hobson, Art. Tales of the Quantum: Understanding Physics’ Most Fundamental Theory (Kindle Locations 96-98). Oxford University Press 2017. Kindle Edition.

[4] There were rebuttals to Hobson’s paper, for example:

Massimiliano Sassoli de Bianchi, “Quantum fields are not fields.”

Because of the experimentally verified presence of entanglement, the so- called fields of several quantum entities are certainly not fields that can be defined in a three-dimensional space, but only in a higher dimensional configuration space. … quantum non-spatiality … what quantum mechanics teaches us is that not all of physical reality is contained within space, and that we need to drop the preconception that so-called microscopic “particles” and quantum “fields” would necessarily be spatial entities.

Am. J. Phys., Vol. 77, No. 10, October 2009. Letters To the Editor. “The Real Scandal of Quantum Mechanics.” Richard Conn Henry, The Johns Hopkins University.

We know for a fact that the universe is not “made of” anything. Get it through your heads, physicists! It is sometimes said that the only thing that is real are the observations, but even that is not true: observations are not real either. They, and everything else, are purely mental.

 

One thought on “Point particles RIP

  1. I’m getting near the end of Hobson’s book Tales of the Quantum, and today’s Space.com article “There and Back Again: Scientists Beam Photons to Space to Test Quantum Theory” exemplifies his point about how wave-particle dualism is treated in textbooks. Add another media reference to that list of sources which have yet to view “the universe as made of fields that sometimes appear to be particles [as ripples in a field which hit like particles].”

    Researchers have taken a famous quantum-physics experiment to new heights by sending light, in the form of photons, to space and back, demonstrating the dual-particle-wave nature of light over much greater distances than scientists can achieve on Earth.

    The light split into two beams, like a wave and, at the same time, stayed together as a single photon, until the end, when the liquid crystal device forced it to behave as one or the other right before hitting the detector. The predictions of quantum theory were vindicated, Vallone said — and the surreal nature of quantum mechanics was reaffirmed.

    The article provides some historical background for this latest earth-space form of the famous double-slit experiment (expansively discussed by Hobson). And notes that the duality depends on how scientists measure photons (which introduces the measurement problem). Then discusses how the behavior is “decided” (or chosen) in the experiment: “Does light commit to one behavior at the beginning of an experiment, when it’s produced; at the end, when it’s detected; or some time in between?” (There is no mention of wave function collapse in the article. And nothing about quantum unity as well.1)

    Superposition is mentioned once: “Vallone’s group … were able to keep the light in its bizarre double state, called a superposition, for 10 milliseconds.” But that statement only confuses the matter, since superposition is a wave phenomenon — some readers’ takeaway might be that the superposition is “wave and particle” rather than a spatially extended quantum.

    The new findings suggest that the behavior of objects in the universe is fundamentally undetermined until something forces them to behave a certain way. Particles propagate like waves, waves coalesce into particles and nothing can be predicted with certainty, only a probability.

    Vallone approaches the concept in a similar manner. “When we think of a photon as a particle, as a little ball, we are [making a] mistake. When we think of a photon like a water wave, we are [also making] a mistake,” he said. “The photon, in some cases, seems to behave like a wave or seems to behave like a particle. But actually, it’s neither.”

    [1] “Despite being extended spatially, a quantum is a single thing, not made of parts. You cannot alter a quantum at just one place. Whatever happens to it happens to the entire quantum.” — Hobson, Art. Tales of the Quantum: Understanding Physics’ Most Fundamental Theory (Kindle Locations 926-928). Oxford University Press. Kindle Edition.

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