On 1/15/2014 4:08 PM, LizR wrote:
On 16 January 2014 03:51, Jesse Mazer <laserma...@gmail.com
On Wed, Jan 15, 2014 at 5:10 AM, LizR <lizj...@gmail.com
On 15 January 2014 22:55, Bruno Marchal <marc...@ulb.ac.be
On 14 Jan 2014, at 22:04, LizR wrote:
Sorry, I realise that last sentence could be misconstrued by
being very nitpicky and looking for irrelevant loopholes to argue
let's try again.
Now how about discussing what I've actually claimed, that the time
of fundamental physics could account for the results obtained in EPR
But you need "hyper-determinism", that is you need to select very
boundary conditions, which makes Cramer's transaction theory close
I'm not sure what you mean by special boundary conditions. The bcs in
type experiment are the device which creates the photons, and the
the measuring apparatuses. These are special but only in that the
entangled ... note that this isn't Cramer's or Bohm's theory (the
theory requires far more complexity that this).
Time symmetry in the laws of physics alone, without any special restriction
boundary conditions, can't get you violation of Bell inequalities. Ordinary
symmetry doesn't mean you have to take into account both future and past to
determine what happens in a given region of spacetime after all, it just
can deduce it equally well going in *either* direction. So in a
time-symmetric theory (Price's speculations about hidden variables are at
compatible with determinism) it's still true that what happens in any
spacetime can be determined entirely by events in its past light cone, say
occurring at some arbitrarily-chosen "initial" tim. This means that in a
theory where measurement results are explained in terms of hidden variables
particles carry with them from emitter to experimenters, it must be true
original "assignment" of the hidden variables to each particle at the
determined by the past light cone of the event of each particle leaving the
Meanwhile, the event of an experimenter choosing which measurement to
have its own past light cone, and there are plenty of events in the past
of the choice that do *not* lie in the past light cone of the particles
So, without any restriction on boundary conditions, one can choose an
possible initial conditions with the following properties:
1. The initial states of all points in space that line in the past light
cone of the
particles leaving the emitter are identical for each member of the
ensemble, so in
every possible history generated from these initial conditions, the
the same hidden variables associated with them.
2. The initial states of points in space that lie in the past light cone of
experimenters choosing what spin direction to measure vary in different
the ensemble, in such a way that all combinations of measurement choices are
represented in different histories chosen from this ensemble.
If both these conditions apply, Bell's proofs that various inequalities
violated works just fine--for example, there's no combination of hidden
you can choose for the particle pair that ensure that in all the histories
experimenters measure along the *same* axis they get opposite results
one experimenter, spin-down for the other) with probability 1, but in all
histories where they measure along two *different* axes they have less than
chance of getting opposite results. Only by having the hidden variables
during emission be statistically correlated to the choices the
make about measurements can Price's argument work, and the argument above
time-symmetry without special boundary conditions won't suffice for this.
If you're right then Price is wrong. However I don't recall him saying that the only
consequence of time symmetry is that events can be, so to speak, worked backwards
equally well. In particular, I read his EPR explanation as showing that both future and
past boundary conditions were relevant in explaining the violations of B's Inequality.
The "forwards-and-backwards" version would prevent time symmetry having any detectable
effects, as far as I can see. (Also I'd like to see an explanation of EPR which works
backwards from the measurement settings to the emitter and explains the violation of B's
Inequality. That would definitely be a clincher!)
You can do that (in fact it may have been done). You have two emitters with polarizers
and a detector at which you post-select only those particles that arrive and form a
singlet. Then you will find that the correlation counts for that subset violates Bell's
inequality for polarizer settings of 30, 60, 120deg.
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