On 1/9/2014 4:19 PM, Jesse Mazer wrote:

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On Tue, Jan 7, 2014 at 7:57 PM, LizR <lizj...@gmail.com <mailto:lizj...@gmail.com>> wrote: On 8 January 2014 12:53, Jesse Mazer <laserma...@gmail.com <mailto:laserma...@gmail.com>> wrote: On Tue, Jan 7, 2014 at 4:35 PM, LizR <lizj...@gmail.com <mailto:lizj...@gmail.com>> wrote: On 8 January 2014 08:59, Jesse Mazer <laserma...@gmail.com <mailto:laserma...@gmail.com>> wrote: Well, most physicists already agrees physics is time-symmetric (well, CPT-symmetric, but the implications are the same for Bell's inequality and thermodynamics), Yes, they do, but it doesn't appear to be taken into account when discussing Bell's inequality. but I don't see how this alone can explain violations of the Bell inequality. No, you need to work out the consequences mathematically, and I dare say that is quite difficult. This is simply a /logical/ demonstration that Bell's inequality can be violated while retaining locality and realism, which is otherwise impossible. As I said in another comment, if you allow information about the state of complex systems like detectors to flow back in times as well as forwards, it's not clear that this really counts as preserving locality. Nothing is flowing either way in time. (Assuming a block universe, nothing /can/ flow in time - the notion doesn't make sense).I think you're reading something into my talk about information "flowing back in time"that I didn't intend. I certainly didn't mean to deny the block universe view of time orsuggest that an imaginary observer viewing all of spacetime "from the outside" (like wemight observe 2D flatland) would see spacetime itself "changing" (as opposed to just aset of frozen worldines as one would expect in a block universe). But the notion ofinformation flowing from one point in spacetime to another doesn't imply any such denialof the block universe, for example David Deutsch, who argues forcefully for the blockuniverse view in his book "The Fabric of Reality", wrote a paper athttp://arxiv.org/abs/quant-ph/9906007 titled "Information Flow in Entangled QuantumSystems". The notion of information flow just requires some type of logical ordering,with one point in spacetime being the event of the information first being "transmitted"and another point being the event of it being "received".There might be no way to define transmission vs. reception of a message at a fundamentalquantum level, but if we're dealing with macroscopic transmitters and receivers of somekind that have a local thermodynamic arrow of time, there shouldn't be a problemdistinguishing them...for instance, the transmitter has to *first* compose the message(perhaps after observing some local event, like the outcome of an election, that themessage is supposed to convey information about) and *then* transmit it, relative to thelocal thermodynamic arrow of time, while the receiver *first* has a sequence of bitscome in which are *then* made sense of. So as long as we can locally define transmissionvs. reception in this way, my talk of information flowing backward in time just meansthat the reception-event is on the past light cone of the transmission-event, andinformation flowing forward would just be the ordinary case of the reception-event beingon the future light-cone of the transmission event. The point is that if both sorts ofinformation-transmission are possible, then I should be able to transmit a message backto be received by a relay, then the relay can transmit a copy of the message forward toa friend light-years away from Earth, such that the friend receives the message on thesame day I sent it (relative to our mutual rest frame), despite being light-years away.It's not obvious that a universe where such things were possible would really count asone that respects "locality", even if each individual message travelled at the speed oflight.

`I don't think that follows. You're imagining yourself moving forward in cosmic entropic`

`time and composing a message that you're going to transmit back in time. But that's`

`inconsistent. What T-symmetry implies is that there is a message whose receipt by you`

`entails that the transmitter in the past who sent it to you also had to send that message`

`to your friend. In a block universe picture is just requires a certain consistency`

`between the messages at the transmitter, you, and your friend. In EPR we're just sending`

`a few particles one-at-a-time. They have to look random to you, which means the "message"`

`you're sending to your friend is random.`

`Of course for this to work there has to be determinism - it would look like this in a`

`Newtonian universe - MWI is in principle deterministic but T-symmetry means reversing all`

`the "worlds" whereas outside of some exotic laboratory situations we only have access to one.`

Locality is preserved so long as no physical objects travel faster than light.I don't think physicists use such a narrow definition--if the equations of QM weremodified so that the EPR experiment could be used to transmit *information* FTL, theneven if no measurable particle or wave was observed to move FTL this would stillprobably be seen as a violation of locality. And the pilot wave in Bohmian mechanics isarguably just a sort of rule for coordinating the behavior of distant particles ratherthan a "physical object", but its ability to coordinate them instantaneously istypically seen as a violation of locality. Unfortunately I have not been able to findany very precise definition of locality that would give a totally clear answer aboutcases like this, it tends to be stated in terms of imprecise terms like "effects" and"influences".

`Think of it in terms of Feynman's path integrals. The path can go from the source to you,`

`back to the source, to your friend, back to the source,...and a lot of other places. But`

`it only reenforces positively along a few paths and those are the ones that show up in one`

`block of the multiverse.`

Brent

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