## New Directions in the Foundations of Physics Conference in Washington DC 2013 (part 5)

### “Lagrangian-Only Quantum Theory” by Ken Wharton

What I liked about Ken’s talk was the novelty of his idea. Working
in the quantum mechanics reconstruction area I always ask the “what if”
questions: what if the universe would obey different kinds of mathematical
relationships? So what if there are no dynamical equations, not even stochastic
ones? This is the premise of Ken’s approach in arXiv:1301.7012.

As an inspiration one can pick the example of statistical
mechanics and work out along the following lines:

1. Consider
all possible microstates

2. Eliminate
inconsistent states

3. Assign
an equal a priori probably

4. Calculate
probabilities as Bayesian updates

Now in nature there are distinguished mathematical
structures, including the existence of Hamiltonian equations of motion. If we
do not consider the dynamics, we can open the door for all kinds of other kinds
of ontologies, like for example simulated virtual realities. By killing the
dynamics Ken is basically going outside the realm of physics in hope to
discover new insights. If I understood him well in a private conversation after
the talk, Ken’s approach is basically opposite that of t`Hoofts: start with a chaotic
system in the IR domain and arrive at quantum mechanics in the UV area. In the
process Ken claims he recovers something that asymptotically becomes Born’s
rule. If correct, this would represent a genuine new insight into the origin of
Born’s rule besides the ones from Gleason theorem or Zurek’s program.

One may object that going outside physics is a fool’s
errand, but then we are reminded by the unphysical PR-boxes which proved
fruitful into better understanding quantum mechanics. Will Ken’s approach prove
as fruitful? Only time will tell and I wish him luck.

One last word about this series of posts from the
conference. Here is the link to the conference page http://carnap.umd.edu/philphysics/conference.html
where one can find all the brief descriptions of the talks.

Thanks for the nice summary, Florin.

ReplyDeleteOne quibble: I'm not sure it's fair to say that dropping dynamics means that one is "going outside the realm of physics". After all, one still has kinematics.

More to the point, I think, when you drop dynamics you're going outside what Smolin calls the "Newtonian Schema", which includes Hamiltonian structures. But I'd argue that there's plenty of "physics" remaining, revolving around the Lagrangian itself. (Hamilton's principle, the Feynman path integral, etc.) For more on the distinction between the Newtonian and Lagrangian Schemas, you might try my essay "The universe is not a computer" at arXiv:1211.7081.

Hi Ken,

ReplyDeleteAbout the realm outside physics, there is nothing wrong with it; in fact I think if used properly it can lead to very lucrative things. I am thinking here on using your results to make stock market predictions for example (many theoretical physicists work in this area). In fact when you gave the talk, I did create a mental model outside physics and I was able to follow most of your talk in that key.

The mental model was the risk assessment process in software development (since I have expert experience in this area). In commercial software development, programmers write the software and quality assurance people try to discover defects. Then from the release perspective one does a risk analysis and determines if the software is ready to be sent to customers. Your talk fitted that risk analysis process very well (and that is why I was thinking it may be extended to create effective stock market tools).

Now there where some assertions in the talk I did disagree with and that is why I told you after that talk that “you lost me on after the dynamic was removed”. Let me qualify that and explain why. What I meant was that after dropping the dynamics my physics intuition evaporated. In http://arxiv.org/abs/1303.3935 I am reconstructing quantum mechanics and I was considering the most general setting for this project. As part of this work I did a careful analysis on the origin of the dynamic. In general the dynamic has to be part of the ontology; otherwise the description of the universe is incomplete. I’ll put your paper on my “to read” list, but until I read it I don’t know if you agree with this or not. However, you can see the same point right away in the QM context if you look at Spekkens’ toy model or Philip Goyal’s research area.

PS: your name was familiar to me but I did not know from where. Now I realized you participated in FQXi’s contests. I did that too and I also had blogged in the past there on QM topics. At FQXi I also had a dispute with Joy Christian about his bogus claim of “disproving Bell’s theorem”.

Ken,

ReplyDeleteOK, I read http://arxiv.org/abs/1211.7081 and now I understand where you are coming from. Maybe it may interest you to read http://arxiv.org/abs/1305.3594. In conjunction with Zurek's program this solves the measurement problem and I'll explain how in subsequent posts.