On 03 Jan 2014, at 13:03, Richard Ruquist wrote:




On Fri, Jan 3, 2014 at 3:13 AM, Bruno Marchal <marc...@ulb.ac.be> wrote:

On 02 Jan 2014, at 17:12, Richard Ruquist wrote:

the properties or measure of particles vanish in between observations.

I am not sure Wheeler has ever believe this. He seem to have come back to the MWI, which provides a realist account of his participatory "interpretation".


It seems to me that It<Bit is an empirically based theory.

OK.



If Wheeler did not think it was empirically correct

OK.


he never would have proposed it.
It<Bit can be consistent with MWI

OK. I can't agree more.




Its measure upon detection-observation is determined by the binary question asked by the observer. If the same question is asked by every MWI observer, an unchanged world with the expected measures is maintained.

But how the "other terms" vanish?


The terms only vanish in between observation.

?
The advantage of Everett is that any interaction can count as an observation. What you say seems a bit weird.



During observation the terms reappear
and are dependent on the question each observer asks .
In a controlled experiment all observers ask the same question
and get the same response, which reveals the inherent quantum probabilities, even in an MWI multiverse. If every observer asks the same question, spacetime does not split.
Or does it?

Not literally. It is our consciousness state which differentiates along the (arithmetical, but not necessarily computable: there is a mix) computational histories.

Bruno





Richard



This would amount to a controlled experiment.

Say have half the observers ask a different question and flip back and forth (for detection of the resulting signal)..
Is that arithmetically possible.

Even if it is, the question is not just the arithmetical possibility (consistency), but it has to be statistically reasonable.

Anyway, if comp is correct, there is no choice. Physics becomes independent of the basic ontology or theory. Deriving physics from a clearly non physical TOE (like arithmetic) ensures the testability of the comp theory.

Bruno





Richard

Jason


Edgar



On Wednesday, January 1, 2014 2:21:33 PM UTC-5, Jason wrote:



On Wed, Jan 1, 2014 at 4:33 AM, LizR <liz...@gmail.com> wrote:
On 1 January 2014 21:34, meekerdb <meek...@verizon.net> wrote:
On 12/31/2013 7:22 PM, LizR wrote:
On 1 January 2014 13:54, meekerdb <meek...@verizon.net> wrote:
Of course in Hilbert space there's no FTL because the system is just one point and when a measurement is performed it projects the system ray onto a mixture of subspaces; spacetime coordinates are just some labels.

I thought there was no FTL in ordinary space, either? (I mean, none required for the MWI?)

Right, but the state in Hilbert space is something like |x1 y1 z1 s1 x2 y2 z2 s2> and when Alice measures s1 at (x1 y1 z1) then s2 is correlated at (x2 y2 z2). As I understand it the MWI advocates say this isn't FTL because this is just selecting out one of infinitely many results |s1 s2>. But the 'selection' has to pair up the spins in a way that violates Bell's inequality.

If I understand correctly ... actually, let me just check if I do, before I go any further, in case I'm talking out my arse. Which wouldn't be the first time.

I assume we're talking about an EPR correlation here?

If yes, I've never understood how the MWI explains this.

The thing to remember is entanglement is the same thing as measurement. The entangled pair of particles have measured each other, but they remain isolated from the rest of the environment (and thus in a superposition, of say UD and DU). Once you as an observer measure either of the two particles, you have by extension measured both of them, since the position, which you measured has already measured the electron, and now you are entangled in their superposition.

Jason


I've see it explained with ASCII diagrams by Bill Taylor on the FOAR forum, and far be it from me to quibble with Bill, but it never made sense to me. Somehow, the various branches just join up correctly...

The only explanation I've come across that I really understand for EPR, and that doesn't violate locality etc is the time symmetry one, where all influences travel along the light cone, but are allowed to go either way in time.

So although I quite like the MWI because of its ontological implications, this is one point on which I am agnostic, because I don't understand the explanation.


In fact, it's generally assumed to be very, very STL (unless light itself is involved). At great distances from the laboratory, one imagines that the superposition caused by whatever we might do to cats in boxes would decay to the level of noise, and fail to spread any further.
That's an interesting viewpoint - but it's taking spacetime instead of Hilbert space to be the arena. If we take the cat, either alive or dead, and shoot it off into space then, as a signal, it won't fall off as 1/r^2.

No, but it will travel STL!

Sure. I was just commenting on the idea that the entanglement has a kind of limited range because of 'background noise'. An interesting idea, similar to one I've had that there is a smallest non-zero probability.

But if you want to get FTL, that's possible if Alice and Bob are near opposite sides of our Hubble sphere when they do their measurements. They are then already moving apart faster than c and will never be able to communicate - with each other, but we, in the middle will eventually receive reports from them so that we can confirm the violation of Bell's inequality.

Hmm, that's a good point. That would, however, fit in nicely with time symmetry (which really needs a nice acronym, I'm not sure "TS" cuts it). I tend to evangelise a bit on time symmetry, but only because everyone else roundly ignores it, and it seems to me that it at least has potential.


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