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Andrew Clough wrote:

<I'd also like to note (since that section was cut out) that I was using

communication with the past to *disprove* quantum entanglement.>

* >> snip <<
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<This does not prove an absolute frame of reference!>

It is possible for a theory to be non-local

and Lorentz invariant at the same time?

When Bohm's non-local approach

is applied to relativistic quantum theory

we find that this theory is not Lorentz-invariant.

Bell's theorem (plus experiments) established

that (realistic) interpretations of QM must be non-local.

There's not, as far as I know, an analogous

*theorem* which proves that (realistic) interpretations

of QM must also be non-Lorentz-invariant.

Anyway an ideal experiment [1,2], by Lucien Hardy,

with 2 interferometers, one electron, one positron,

suggests that the simultaneous measurement

on these particles implies a preferred reference

frame (but does not tell us which frame is).

Another ideal device [3], by Ian Percival, consisting

in a double Bell-type experiment, with moving apparatuses

and linked outcomes, also suggests the existence of

a preferred refernce frame.

Now if there is a preferred reference frame, as implied

by these gedanken experiments, causal paradoxes

(such as backward causation, sending information

backward in time) are blocked.

The possible candidate for such a preferred reference

frame is the cosmic frame (as Bohm used to call it) and

especially the one in which the cosmic background

radiation is isotropic.

Notice that Wheeler [4] considered the possibility that

entanglement might occur on cosmological scales.

[1] Lucien Hardy, Phys. Rev. Lett., (1992), vol. 68, n. 20,

pages 2981 - 2984

[2] Hardy's "theorem" or "paradox" or "experiment" is also

discussed at http://arxiv.org/abs/quant-ph?0104062

(with pictures)

[3] I.C. Percival, http://arxiv.org/abs/quant-ph?9811089

[4] J.A.Wheeler, Law without law, in "Quantum Theory

and Measurement", Wheeler and Zurek eds., Princeton

U.P., 1983.

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