Before I kick the bucket, I want to figure out how these frameworks fit together:
classical mechanics
classical statistical mechanics
classical field theory
quantum mechanics
quantum statistical mechanics
quantum field theory
thermodynamics
and probably some more. For example, one famous weird thing is that if you take classical statistical mechanics and replace
1/(Boltzmann's constant × temperature)
with
i × Planck's constant × time
in all your equations, you get quantum mechanics - more or less. So if you ignore the constants, this is saying that "imaginary time" - whatever the hell that is! - acts like "inverse temperature".
Physicists use this fact a lot, but remain divided on whether it's "just a trick". I don't think something this big can be just a trick!
But there are other ways to set up this analogy. I wrote a paper with Blake Pollard where instead we said inverse temperature is analogous to i × Planck's constant. We pushed this other analogy to the point of figuring out what in quantum mechanics corresponds to 𝑒𝑛𝑡𝑟𝑜𝑝𝑦 in classical statistical mechanics. We called it "quantropy", and worked out this nice chart.
But now I'm wishing we hadn't set Boltzmann's constant equal to 1. And I want to compare our analogy to the usual one, and figure out what the hell is going on. When there are multiple mathematically rigorous analogies between frameworks you should get serious and study them all, not just pick one and ignore the rest.
I'm also annoyed that we didn't notice that the thing analogous to free energy, which I called "free action" or Φ, is what physicists call the "effective action".
Here's our paper:
https://arxiv.org/abs/1311.0813