Hi Michael,
> Title not withstanding, you are not really arguing against the universe as literally a computer a la Lloyd or Wolfram. You only indirectly argue against them by positing a block universe, which certainly can't be computed.
I'm not sure I'm reading that correctly; surely you're not saying that there are no block universes that can be computed? Wolframs universes are block universes, and can be computed. Newtonian clockwork universes are also in that category. But as I said above, the block-universe has little or nothing to do with any of this.
>Now, you admit in your reply to me that you don't have a novel argument for block universe, though I assume you want that to be a distinguishing feature of LSU.
No, please don't assume that. Again, re-read my first response; physics is *all* block-universes, NSU, LSU, the lot. I don't need to argue for it, because it's not a distinguishing feature.
> In other words, there can be block worlds without local time-symmetric processes and there are time-symmetric accounts of QM that are not block world.
Yes on the first, no on the second (at least, any such account would also have a corresponding block-world account). At least, no one has ever come up with such a physical theory. (One would need two time dimensions, at which point time-symmetry would mean something quite different.)
> since we already knew that a time-symmetric psi-epistemic account of the QM could deflate the MP and provide a local picture of entanglement, that can't be your novel conclusion.
Maybe you know this, but this is still heresy in much of the foundations community. Regardless, I was more trying to answer the essay question than provide a 'novel conclusion'. The question is what flawed assumption we might be making without realizing it, and the answer is the assumption that the universe operates according to the Newtonian Schema. You may be one of the few people who have already internalized this point, but even many people in the retrocausal-quantum-camp still lapse into NSU-style thinking with alarming regularity. And people not in the camp are repelled from it, I think, because they think NSU is the only way to do physics.
> here's my challenge to you. If the lagrangian density L is a function of the field f and its derivatives, S is stationary wrt to f (LS formalism), and f satisfies the boundary conditions (LS formalism), then L satisfies a differential eqn (NS formalism). If you want your LS soln to allow for a continuously mediated (3+1)D story, then I don't see how L won't be a function of f and its derivatives, thus allowing for an NS counterpart. Can you explain how you plan to avoid this LS-NS correspondence?
The mistake is that you are assuming S has to be stationary with respect to small variations of f. True, this is how one gets classical field equations in classical physics, but it's simply not true when you look at the full quantum path integral (unless you take the hbar->0 limit, which is not physical.) Without that assumption, one cannot derive any equations of motion at all, and there simply is no NS version of a generic LS approach where the action isn't extremized. (We can debate whether the standard path integral still maps to the Schrodinger equation, but this is again beside the point, because LS is a broad framework that subsumes more than just the standard path integral; there will be other ways to use the action that lead to no general equations at all.)
I'm denying the existence of some master equation of motion that applies in all cases. No equations, no NS. It's that simple.
I'll tackle the RBW discussion back in email... but as I've told you, I'm not about to throw out all continuously-mediated LSU approaches until I have no other choice.
Cheers,
