Ken Wharton
@kenwharton.bsky.social
Physics professor at San Jose State. Quantum Foundations. Big fan of space and time, and also many things therein.
I liked your 'cell vs DNA' analogy, but if you push the analogy to where the 3D cell turns into a full 4D history, you need to be very careful about not accidentally ending up with two different time dimensions in the analysis. I think it can be done -- see the below essay -- but it requires care.
The Universe is not a Computer
When we want to predict the future, we compute it from what we know about the present. Specifically, we take a mathematical representation of observed reality, plug it into some dynamical equations, a...
arxiv.org
November 11, 2025 at 11:11 PM
I liked your 'cell vs DNA' analogy, but if you push the analogy to where the 3D cell turns into a full 4D history, you need to be very careful about not accidentally ending up with two different time dimensions in the analysis. I think it can be done -- see the below essay -- but it requires care.
I enjoyed the talk! Does this view push you towards viewing a full “history” as more fundamental/meaningful than a typical “state”? If so, are you inclined to look to path integrals or the consistent-history formalism as potential starting points for the shift that you’re advocating?
November 11, 2025 at 11:04 PM
I enjoyed the talk! Does this view push you towards viewing a full “history” as more fundamental/meaningful than a typical “state”? If so, are you inclined to look to path integrals or the consistent-history formalism as potential starting points for the shift that you’re advocating?
Well, for one, the field-version of the path integral is something that needs a lot more analysis. I've published several papers on the particle-based path-integral, which motivates a very different foundational perspective, on entanglement in particular. arxiv.org/abs/2206.02945
Entanglement and the Path Integral
The path integral is not typically utilized for analyzing entanglement experiments, in part because there is no standard toolbox for converting an arbitrary experiment into a form allowing a simple su...
arxiv.org
November 11, 2025 at 5:41 PM
Well, for one, the field-version of the path integral is something that needs a lot more analysis. I've published several papers on the particle-based path-integral, which motivates a very different foundational perspective, on entanglement in particular. arxiv.org/abs/2206.02945
Sadly, there’s been very little work done on quantum foundations in a QFT context. If you’re looking for a wide-open research field with lots of low-hanging fruit, that might be something to consider.
November 11, 2025 at 4:52 PM
Sadly, there’s been very little work done on quantum foundations in a QFT context. If you’re looking for a wide-open research field with lots of low-hanging fruit, that might be something to consider.
The foundational difficulties with QM don’t just vanish when you switch to QFT. In many ways they get worse. Both theories need some sort of rule-breaking slight-of-hand to extract our spacetime-based empirical reality from the mathematical formalism.
November 11, 2025 at 4:52 PM
The foundational difficulties with QM don’t just vanish when you switch to QFT. In many ways they get worse. Both theories need some sort of rule-breaking slight-of-hand to extract our spacetime-based empirical reality from the mathematical formalism.
Because you need to take a view like that at some point if you’re ever going to resolve the measurement problem as applied to quantum fields. Just because it’s not justified by the rules of QFT doesn’t mean it’s wrong. After all, QFT’s story of “reality” is just as internally-incoherent as QM’s.
November 11, 2025 at 5:10 AM
Because you need to take a view like that at some point if you’re ever going to resolve the measurement problem as applied to quantum fields. Just because it’s not justified by the rules of QFT doesn’t mean it’s wrong. After all, QFT’s story of “reality” is just as internally-incoherent as QM’s.
In some ways your concern here is analogous to analyzing the heat equation without any knowledge that there’s an underlying particle-based explanation of heat. That equation also predicts faster-than-light influences. Almost makes you wonder if we’re missing an underlying story in QFT, too. ;-)
November 11, 2025 at 12:44 AM
In some ways your concern here is analogous to analyzing the heat equation without any knowledge that there’s an underlying particle-based explanation of heat. That equation also predicts faster-than-light influences. Almost makes you wonder if we’re missing an underlying story in QFT, too. ;-)
The one story I heard was that he was embarrassed for SLAC to have to pay the page proof expenses, so he submitted it to this brand new PPF journal (with waived fees) instead of something more established. But I don't know anything about the Madison connection.
November 7, 2025 at 10:41 PM
The one story I heard was that he was embarrassed for SLAC to have to pay the page proof expenses, so he submitted it to this brand new PPF journal (with waived fees) instead of something more established. But I don't know anything about the Madison connection.
Bell was officially at SLAC that year, on Sabbatical from CERN, but travelled around a bit from there. Do you know how long he was in Madison?
November 7, 2025 at 10:33 PM
Bell was officially at SLAC that year, on Sabbatical from CERN, but travelled around a bit from there. Do you know how long he was in Madison?
Or at least with tenure / job security... :-)
November 4, 2025 at 12:38 AM
Or at least with tenure / job security... :-)
Didn't Emily explain it well in her book? I noticed you didn't talk much about that section in your long review. Anyways, I'm more than happy to try to help clarify the terminology... just ask! :-)
October 25, 2025 at 8:58 PM
Didn't Emily explain it well in her book? I noticed you didn't talk much about that section in your long review. Anyways, I'm more than happy to try to help clarify the terminology... just ask! :-)
There are several classes of models that would get rid of an ontic configuration space. After all, such spaces are precisely how one would formalize incomplete knowledge of 3D classical states. Here’s a link to my 2020 Rev Mod Phys piece which categorizes such “spacetime-based” reformulations.
Bell's Theorem and Locally-Mediated Reformulations of Quantum Mechanics
Bell's Theorem rules out many potential reformulations of quantum mechanics, but within a generalized framework, it does not exclude all "locally-mediated" models. Such models describe the correlation...
arxiv.org
October 23, 2025 at 8:36 PM
There are several classes of models that would get rid of an ontic configuration space. After all, such spaces are precisely how one would formalize incomplete knowledge of 3D classical states. Here’s a link to my 2020 Rev Mod Phys piece which categorizes such “spacetime-based” reformulations.
Maybe every “interpretation” of the wavefunction has this problem (depending how you define that) but not every possible “reformulation”. There’s no configuration space in the path integral formulation, for instance. Models can aim to explain quantum phenomena without interpreting wavefunctions.
October 23, 2025 at 8:34 PM
Maybe every “interpretation” of the wavefunction has this problem (depending how you define that) but not every possible “reformulation”. There’s no configuration space in the path integral formulation, for instance. Models can aim to explain quantum phenomena without interpreting wavefunctions.
That’s a good case for MWI. I’m in full agreement with this observation that the “main weirdness” is that one needs an exponentially large configuration space (plus time) instead of something that fits in our observed 4D universe. But it’s not fair to say that every approach has this problem.
October 23, 2025 at 8:34 PM
That’s a good case for MWI. I’m in full agreement with this observation that the “main weirdness” is that one needs an exponentially large configuration space (plus time) instead of something that fits in our observed 4D universe. But it’s not fair to say that every approach has this problem.
Interesting question! As I see it, many different causal models are consistent with E&M. (The causation isn't in the bare equations, those are just correlations.) Different cases evidently call for different causal models (controlling particles with lasers, controlling fields with charges, etc.)
October 14, 2025 at 3:40 AM
Interesting question! As I see it, many different causal models are consistent with E&M. (The causation isn't in the bare equations, those are just correlations.) Different cases evidently call for different causal models (controlling particles with lasers, controlling fields with charges, etc.)
Who knows? No one knows the right ontological model of what is "really" happening when we're not looking. My point is that if you are just looking at absorption phenomena, and trying to model them using classical E&M, there is motivation to consider causal models with future inputs/constraints.
October 14, 2025 at 3:36 AM
Who knows? No one knows the right ontological model of what is "really" happening when we're not looking. My point is that if you are just looking at absorption phenomena, and trying to model them using classical E&M, there is motivation to consider causal models with future inputs/constraints.
So, if I'm consistent in my application of causal logic, every time I see a photoelectric effect I should infer that I should use final-field-inputs (at least in part), to explain the observations. Using final-field causal inputs is actually a lot simpler than ditching classical E&M entirely.
October 14, 2025 at 12:08 AM
So, if I'm consistent in my application of causal logic, every time I see a photoelectric effect I should infer that I should use final-field-inputs (at least in part), to explain the observations. Using final-field causal inputs is actually a lot simpler than ditching classical E&M entirely.
But here's the thing: this 'time-reversed movie' I mentioned doesn't just happen when I play an emission event backwards. The same situation appears in real life, every time an array of atoms actually absorbs a photon! That's the photoelectric effect, an empirical fact.
October 14, 2025 at 12:06 AM
But here's the thing: this 'time-reversed movie' I mentioned doesn't just happen when I play an emission event backwards. The same situation appears in real life, every time an array of atoms actually absorbs a photon! That's the photoelectric effect, an empirical fact.
If I took a movie of this and played it in reverse, despite the apparent advanced field, I'd reach the same conclusion. The way to explain a convergence of the field (onto one particle) would be to use a *final* field input. (Final in the time-reversed movie, meaning "initial" originally.)
October 14, 2025 at 12:01 AM
If I took a movie of this and played it in reverse, despite the apparent advanced field, I'd reach the same conclusion. The way to explain a convergence of the field (onto one particle) would be to use a *final* field input. (Final in the time-reversed movie, meaning "initial" originally.)
Okay, now, replace the charges with a bunch of excited atoms, in some metastable state. One atom decays. A classical E&M model is still pretty good here. A similar initial-field-input causal model is needed to explain the pattern of where the field can eventually be detected.
October 13, 2025 at 11:58 PM
Okay, now, replace the charges with a bunch of excited atoms, in some metastable state. One atom decays. A classical E&M model is still pretty good here. A similar initial-field-input causal model is needed to explain the pattern of where the field can eventually be detected.
Yes, exactly. If you use a causal model with a different field input, you won't get the retarded solution. And notice it's not a Cauchy problem! The particle input isn't all at the beginning, it's a full worldline. (And if I told you I shook the particle with a laser, that's another deal entirely.)
October 13, 2025 at 11:53 PM
Yes, exactly. If you use a causal model with a different field input, you won't get the retarded solution. And notice it's not a Cauchy problem! The particle input isn't all at the beginning, it's a full worldline. (And if I told you I shook the particle with a laser, that's another deal entirely.)
Now, I want to causally model this experiment, in this region of spacetime (without zooming out to the whole universe!), recovering the observed retarded fields from my model output. What model “inputs” should I therefore use? (Think about both field inputs and 4-current inputs.)
October 13, 2025 at 11:15 PM
Now, I want to causally model this experiment, in this region of spacetime (without zooming out to the whole universe!), recovering the observed retarded fields from my model output. What model “inputs” should I therefore use? (Think about both field inputs and 4-current inputs.)