View Full Version : Causal basis for Nonlocality? A conjecture from d-branes
Gene Partlow
Oct16-04, 07:15 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>It\'s clear from from the Aspect-type experiments, guided by\nBell\'s work, that our universe is \'nonlocal\', contrary to EPR\'s\ncontention. An example being that if two particles are \'entang-\nled\', though greatly separated in space-time, the measurement\nof some parameter of one particle\'s wavefunction (psi), eg:\nspin orientation, will result in the second particle having a value\ncorrelating with that of the first particle. This is apparently true\nno matter how great their separation...kilometers or thousands\nof light years. And as far as anyone can tell, the effect is some-\nhow communicated \'instantaneously\'.\n\n[Moderator\'s note: All these entangled EPR experiments are simply\nand correctlydescribed by quantum mechanics or quantum field theory (QED).\nWe call theories like QED "local quantum field theories" exactly\nbecause there is *no* way how to send physical superluminal signals.\n\nThe states in the Hilbert space may correlate distant regions in\nspace, but the dynamics - the way how this state evolves -\nrespects causality and locality. An easy way to see it is to\nthink in terms of the Heisenberg picture in which the operators\nevolve much like in classical physics, and the operator at\npoint P in spacetime is only affected by the past light cone of P.\nBecause the commutators are relativistic, too, you will see that\nall the rules of special relativity are perfectly preserved.\nThe feeling that you are sending information superluminally\nis just an illusion, caused by your imagining that the wavefunction\nis a real object that must be changed appropriately before the\nsecond measurement is performed. But in reality, the wavefunction\nis *not* a real object, but just a tool to predict probabilities\nof various outcomes. As clear from the comments above, the probabilistic\nnature of the wavefunction - that physically only exists once the\nmeasurement is done - is essential for quantum field theory to\nagree with special relativity. LM]\n\nSome theorists would say the first particle\'s psi, experiencing a\nchange (~collapse), then propagates that *change* at super-\nluminal velocity to its entangled partner. There are some\nknotty problems with superluminal propagation in our uni-\nverse. Other theorists would claim that nothing is propag-\nated at all.\n\n[Moderator\'s note: Some people may be speculating about various\ncrazy de Broglie-Bohmian theories, but if they\'re physicists, they\nshould still agree about verified physical results. The results are\nthat entanglement exists just like quantum mechanics predicts;\nno physical signals can be sent superluminally just like special\nrelativity requires; the formalism of quantum field theory makes\nquantum mechanics, locality, causality, and Lorentz invariance\nmanifest. Let me say that the text below does not really make\nsense to me. It involves the D-branes and the purpose is probably\nto create a new Universe in which all the laws of locality and\nspecial relativity are violated. It\'s not clear what\'s the purpose\nof these apparently disastrously unphysical theories, and therefore\nthe text below is rated as a weird speculation. String theory\nmay allow non-localities at stringy distances, or bigger nonlocalities\nin the presence of the horizons, but none of them will change the\nbasic facts about the EPR experiments. Papers like one by David\nGross and Ted Erler http://arxiv.org/abs/hep-th/0406199 indicate\nthat string theory, written in some well-chosen light-cone coordinates,\nrespects locality even exactly (well, open string field theory). LM]\n\nI wonder if one way of getting around this may be to think\nabout our universe as being a d-brane in the M-theory sense.\nFurther, there would need to be a very large (probably infinite)\nset of d-brane universes, whose interconnectivity is as yet un-\ndetermined by theory so far. While for certain modeling reasons\ninspired by the dark matter problem, I favor a certain evolution-\nary ordering in the arrangement of all d-brane universes, I be-\nlieve that even a completely randomized ordering could plaus-\nibly support a causal interpretation of nonlocality, consistent\nwith special relativity.\n\nMy qualitative argument is this: Let\'s follow common conjec-\ntures (eg: Linde and many others) that out of a possible infinite\nset of universes, a given newborn universe may acquire a set of\npermanent values for its fundamental parameters (Co, hbar, G,\netc.) out of an effectively randomized and infinite grab-bag of\npossibilities. This implies, for example, that a universe may\nacquire a field-free value for Co anywhere from ~zero to infinite\nvelocity. Thus there would be far more (perhaps infinitely\nmore) d-branes having Co values far greater than that for any\ngiven Co in any specific d-brane. Even in a random brane\narrangement, this would be true for most d-branes happening\nto be \'adjacent\' to our universe in a higher dimensional and\npossibly a higher topological embedding.\n\nNow we know also that, while the sub-atomic particles of a d-\nbrane are stuck on that brane, and cannot propagate outside of\nit, those particles\' wavefunctions can indeed propagate into\nother branes. The consequences of this for particles living in\nother branes are intriguing and being studied by M-theorists.\nBut the one I focus on here hinges on the postulate that changes\nin a particle\'s psi may always propagate away at the local vel-\nocity of light. So..\n\n....When the psi of entangled particle A changes, that change\nimmediately travels out at the velocity of light Co. However, it\nalso travels out into other branes b_n, in directions which are\nby definition orthogonal to our universe frame. The local velo-\ncity of light Co(b_n) in these branes, is overwhelmingly likely to\nbe >>> Co in the original brane containing the entangled pair.\nThus our psi will be traveling at far higher Co_b\'s in other\nbranes. Finally, there is always a non-zero probability that\nour propagating psi-\'ripple\' will find its way back into our brane\nat the location of particle B (the second member of the pair),\neven if it is now many light years away.\n\nEssentially, the first particle communicates information to the\nsecond particle, without violating special relativity, by effec-\ntively *short circuiting* the local brane pathways. It still obeys\nlocal special relativity in each brane it travels through. The\nresult then would be virtually indistinguishable from instan-\ntaneous propagation, as far as any observers in the particles\'\nown universe are concerned.\n\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>It's clear from from the Aspect-type experiments, guided by
Bell's work, that our universe is 'nonlocal', contrary to EPR's
contention. An example being that if two particles are 'entang-
led', though greatly separated in space-time, the measurement
of some parameter of one particle's wavefunction (\psi), eg:
spin orientation, will result in the second particle having a value
correlating with that of the first particle. This is apparently true
no matter how great their separation...kilometers or thousands
of light years. And as far as anyone can tell, the effect is some-
how communicated 'instantaneously'.
[Moderator's note: All these entangled EPR experiments are simply
and correctlydescribed by quantum mechanics or quantum field theory (QED).
We call theories like QED "local quantum field theories" exactly
because there is *no* way how to send physical superluminal signals.
The states in the Hilbert space may correlate distant regions in
space, but the dynamics - the way how this state evolves -
respects causality and locality. An easy way to see it is to
think in terms of the Heisenberg picture in which the operators
evolve much like in classical physics, and the operator at
point P in spacetime is only affected by the past light cone of P.
Because the commutators are relativistic, too, you will see that
all the rules of special relativity are perfectly preserved.
The feeling that you are sending information superluminally
is just an illusion, caused by your imagining that the wavefunction
is a real object that must be changed appropriately before the
second measurement is performed. But in reality, the wavefunction
is *not* a real object, but just a tool to predict probabilities
of various outcomes. As clear from the comments above, the probabilistic
nature of the wavefunction - that physically only exists once the
measurement is done - is essential for quantum field theory to
agree with special relativity. LM]
Some theorists would say the first particle's \psi, experiencing a
change (~collapse), then propagates that *change* at super-
luminal velocity to its entangled partner. There are some
knotty problems with superluminal propagation in our uni-
verse. Other theorists would claim that nothing is propag-
ated at all.
[Moderator's note: Some people may be speculating about various
crazy de Broglie-Bohmian theories, but if they're physicists, they
should still agree about verified physical results. The results are
that entanglement exists just like quantum mechanics predicts;
no physical signals can be sent superluminally just like special
relativity requires; the formalism of quantum field theory makes
quantum mechanics, locality, causality, and Lorentz invariance
manifest. Let me say that the text below does not really make
sense to me. It involves the D-branes and the purpose is probably
to create a new Universe in which all the laws of locality and
special relativity are violated. It's not clear what's the purpose
of these apparently disastrously unphysical theories, and therefore
the text below is rated as a weird speculation. String theory
may allow non-localities at stringy distances, or bigger nonlocalities
in the presence of the horizons, but none of them will change the
basic facts about the EPR experiments. Papers like one by David
Gross and Ted Erler http://arxiv.org/abs/http://www.arxiv.org/abs/hep-th/0406199 indicate
that string theory, written in some well-chosen light-cone coordinates,
respects locality even exactly (well, open string field theory). LM]
I wonder if one way of getting around this may be to think
about our universe as being a d-brane in the M-theory sense.
Further, there would need to be a very large (probably infinite)
set of d-brane universes, whose interconnectivity is as yet un-
determined by theory so far. While for certain modeling reasons
inspired by the dark matter problem, I favor a certain evolution-
ary ordering in the arrangement of all d-brane universes, I be-
lieve that even a completely randomized ordering could plaus-
ibly support a causal interpretation of nonlocality, consistent
with special relativity.
My qualitative argument is this: Let's follow common conjec-
tures (eg: Linde and many others) that out of a possible infinite
set of universes, a given newborn universe may acquire a set of
permanent values for its fundamental parameters (Co, \hbar, G,
etc.) out of an effectively randomized and infinite grab-bag of
possibilities. This implies, for example, that a universe may
acquire a field-free value for Co anywhere from ~zero to infinite
velocity. Thus there would be far more (perhaps infinitely
more) d-branes having Co values far greater than that for any
given Co in any specific d-brane. Even in a random brane
arrangement, this would be true for most d-branes happening
to be 'adjacent' to our universe in a higher dimensional and
possibly a higher topological embedding.
Now we know also that, while the sub-atomic particles of a d-
brane are stuck on that brane, and cannot propagate outside of
it, those particles' wavefunctions can indeed propagate into
other branes. The consequences of this for particles living in
other branes are intriguing and being studied by M-theorists.
But the one I focus on here hinges on the postulate that changes
in a particle's \psi may always propagate away at the local vel-
ocity of light. So..
....When the \psi of entangled particle A changes, that change
immediately travels out at the velocity of light Co. However, it
also travels out into other branes b_n, in directions which are
by definition orthogonal to our universe frame. The local velo-
city of light Co(b_n) in these branes, is overwhelmingly likely to
be >>> Co in the original brane containing the entangled pair.
Thus our \psi will be traveling at far higher Co_b's in other
branes. Finally, there is always a non-zero probability that
our propagating \psi-'ripple' will find its way back into our brane
at the location of particle B (the second member of the pair),
even if it is now many light years away.
Essentially, the first particle communicates information to the
second particle, without violating special relativity, by effec-
tively *short circuiting* the local brane pathways. It still obeys
local special relativity in each brane it travels through. The
result then would be virtually indistinguishable from instan-
taneous propagation, as far as any observers in the particles'
own universe are concerned.
Lubos Motl
Oct16-04, 09:40 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>Gene Partlow wrote:\n\n> It\'s clear from from the Aspect-type experiments, guided by\n> Bell\'s work, that our universe is \'nonlocal\', contrary to EPR\'s\n\nI\'ve posted an article about entanglement and causality on my blog,\nhttp://motls.blogspot.com/\n________________________________________________ ______________________________\nE-mail: lumo@matfyz.cz fax: +1-617/496-0110 Web: http://lumo.matfyz.cz/\neFax: +1-801/454-1858 work: +1-617/384-9488 home: +1-617/868-4487 (call)\n^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Gene Partlow wrote:
> It's clear from from the Aspect-type experiments, guided by
> Bell's work, that our universe is 'nonlocal', contrary to EPR's
I've posted an article about entanglement and causality on my blog,
http://motls.blogspot.com/
__{_______________________________________________ _____________________________}
E-mail: lumo@matfyz.cz fax: +1-617/496-0110 Web: http://lumo.matfyz.cz/
eFax: +1-801/454-1858 work: +1-617/384-9488 home: +1-617/868-4487 (call)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Ilja Schmelzer
Oct19-04, 09:41 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>"Gene Partlow" <stargene@earthlink.net> schrieb\n\n> It\'s clear from from the Aspect-type experiments, guided by\n> Bell\'s work, that our universe is \'nonlocal\', contrary to EPR\'s\n> contention.\n>\n> [Moderator\'s note: All these entangled EPR experiments are simply\n> and correctly described by quantum mechanics or quantum field\n> theory (QED).\n\nWhich are not realistic theories in the sense of EPR and Bell.\n\n[Moderator\'s note: That\'s right: realistic (in the sense of EPR and Bell)\nimplies "non-quantum", and because QED is a quantum theory, it is\nnot realistic in the sense of EPR and Bell. No theory compatible with\nthe observations can be "realistic" in that sense. The term "realistic"\nis deeply unfortunate because it creates the impression that there is\nsomething good about it. By the way, this discussion is off-topic, and\nthis posting is probably the last one in this thread. LM]\n\n> As clear from the comments above, the probabilistic\n> nature of the wavefunction - that physically only exists once the\n> measurement is done - is essential for quantum field theory to\n> agree with special relativity. LM]\n\nQM makes only predictions about probabilities, it does not\ntell us anything about the ontological status of the wave\nfunction.\n\n[Moderator\'s note: Quantum mechanics tells us quite precisely what is\nthe ontological status of the wavefunction. The wavefunction is\na mathematical tool to calculate the probabilities of different outcomes\nof the experiments. Quantum mechanics also tells us unequivocally\nthat any other "materialistic" or "realistic" interpretation of the\nwavefunction, like those advocated in your posting, is incorrect. LM]\n\nClaims that "the wavefunction only exists once\nthe measurement is done" are (usually inconsistent)\ninterpretations of QM, not statements of QM.\n\n[Moderator\'s note: the probabilistic meaning of the wavefunction is\na postulate and a basic rule of quantum mechanics. It is not only\nconsistent; it is inevitable and forced upon us. One can develop\ndifferent mental pictures how to imagine that the probabilities\nfollow from the wavefunction; nevertheless, this probabilistic meaning\nmust be the result. LM]\n\n> [Moderator\'s note: Some people may be speculating about various\n> crazy de Broglie-Bohmian theories, but if they\'re physicists, they\n> should still agree about verified physical results.\n\nThere is nothing cracy in Bohmian mechanics. It is a nice and\nsimple realistic, deterministic theory.\n\n[Moderator\'s note: The only truly clear problem is that it is wrong.\nAnd incidentally, to say that the Bohmian models are "nice and simple"\ncan only be understood as a bad joke. These models introduce a lot of\nunphysical and inconsequential garbage; even Einstein, who otherwise\ndisliked the probabilistic interpretation, called the Bohmian models\n"unnecessary superstructure". LM]\n\nYou may not like it, but it proves that all that anti-realistic quantum\nmystery is not forced on us by observation but a deliberate metaphysical\nchoice.\n\n[Moderator\'s note: On the contrary. The experiments have proved that\nthese "realistic" models cannot be consistent with this real Universe as\nlong as at least elementary artifacts of locality are preserved (which is\nprobably necessary for Lorentz invariance, which is tested as well).\nOne may not like the quantum laws of this Universe, but the only thing\nshe can do about it is to try to move into a different Universe. LM]\n\n> the formalism of quantum field theory makes\n> quantum mechanics, locality, causality, and Lorentz invariance\n> manifest.\n\nThere are QFT variants which use manifest Lorentz invariance,\nbut there is as well the possibility to use a preferred frame.\n\n[Moderator\'s note: There cannot exist a hidden variable theory that\nis able to violate Bell\'s inequalities (which is necessary to agree\nwith observations), but that is also preserving Lorentz invariance\n(even manifestly). This statement is the content of Bell\'s theorem,\nas long as you realize that physical non-locality - the ability to\nsend physical signals superluminally - violates the rules of special\nrelativity. Special relativity and quantum mechanics are allies, and\nthey must work together, in order to agree with experiments. See: ]\n\nhttp://motls.blogspot.com/2004/10/causality-and-entanglement_16.html\n\n> I wonder if one way of getting around this may be to think\n> about our universe as being a d-brane in the M-theory sense.\n\nNo, there is no such way. The proof of Bell\'s inequality does\nnot use any ideas about the way QM or QFT or string theory\ndescribes the entangled two-particle states. It is a very simple\nproof which uses only correlations between classical, macroscopic\nevents (results of measurements, decisions of experimenters)\nand very general assumptions about reality:\n\n<f(A,B)> = int rho(x) f(A(x,a),B(x,b)) dx\n\nwhere x describes reality, rho is a probability distribution\non it, A and B are the observed (macroscopic) results of\nthe observations, a and b the (also macroscopic) choices\nof the experimenters what to measure.\n\nHere realism requires\n\n<f(A,B)> = int rho(x) f(A(x,a,b),B(x,a,b)) dx\n\nand Einstein causality leads to the restriction that A should\nnot depend on b and reverse.\n\nx is in some X which is some set with a probability measure\nrho(x). The nature of X is completely open, there is no\nconnection between X and our spacetime. No branes no\nstrings no quantum foam of multiple universes will be able\nto improve anything.\n\nOr you decide to define a realistic theory, that means,\na theory which defines some ontology X and some\nprobability measure on it to explain the observable effects,\nthen you have to give up Einstein causality on the ontological\nlevel (and have only a restricted Einstein causality for\nobservables). This is the way of Bohmian mechanics, which\nproves that this alternative exists. Or you have to give up\nrealism. But there is no reason for this except the wish to\nimmunize SR.\n\n> My qualitative argument is this: Let\'s follow common conjec-\n> tures (eg: Linde and many others) that out of a possible infinite\n> set of universes, a given newborn universe may acquire a set of\n> permanent values for its fundamental parameters (Co, hbar, G,\n> etc.) out of an effectively randomized and infinite grab-bag of\n> possibilities. This implies, for example, that a universe may\n> acquire a field-free value for Co anywhere from ~zero to infinite\n> velocity. Thus there would be far more (perhaps infinitely\n> more) d-branes having Co values far greater than that for any\n> given Co in any specific d-brane. Even in a random brane\n> arrangement, this would be true for most d-branes happening\n> to be \'adjacent\' to our universe in a higher dimensional and\n> possibly a higher topological embedding.\n>\n> Now we know also that, while the sub-atomic particles of a d-\n> brane are stuck on that brane, and cannot propagate outside of\n> it, those particles\' wavefunctions can indeed propagate into\n> other branes. The consequences of this for particles living in\n> other branes are intriguing and being studied by M-theorists.\n> But the one I focus on here hinges on the postulate that changes\n> in a particle\'s psi may always propagate away at the local vel-\n> ocity of light. So..\n>\n> ...When the psi of entangled particle A changes, that change\n> immediately travels out at the velocity of light Co. However, it\n> also travels out into other branes b_n, in directions which are\n> by definition orthogonal to our universe frame. The local velo-\n> city of light Co(b_n) in these branes, is overwhelmingly likely to\n> be >>> Co in the original brane containing the entangled pair.\n> Thus our psi will be traveling at far higher Co_b\'s in other\n> branes. Finally, there is always a non-zero probability that\n> our propagating psi-\'ripple\' will find its way back into our brane\n> at the location of particle B (the second member of the pair),\n> even if it is now many light years away.\n>\n> Essentially, the first particle communicates information to the\n> second particle, without violating special relativity, by effec-\n> tively *short circuiting* the local brane pathways. It still obeys\n> local special relativity in each brane it travels through. The\n> result then would be virtually indistinguishable from instan-\n> taneous propagation, as far as any observers in the particles\'\n> own universe are concerned.\n\nSounds interesting but does not change the basic problem.\nOr you define some space X with some probability measure\nrho(x) on it, consisting of branes, particles, wave functions on\nthem in whatever dimensions you like, in this case you have\nto reject Einstein causality, or you don\'t, in this case you reject\nrealism.\n\nIlja\n\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>"Gene Partlow" <stargene@earthlink.net> schrieb
> It's clear from from the Aspect-type experiments, guided by
> Bell's work, that our universe is 'nonlocal', contrary to EPR's
> contention.
>
> [Moderator's note: All these entangled EPR experiments are simply
> and correctly described by quantum mechanics or quantum field
> theory (QED).
Which are not realistic theories in the sense of EPR and Bell.
[Moderator's note: That's right: realistic (in the sense of EPR and Bell)
implies "non-quantum", and because QED is a quantum theory, it is
not realistic in the sense of EPR and Bell. No theory compatible with
the observations can be "realistic" in that sense. The term "realistic"
is deeply unfortunate because it creates the impression that there is
something good about it. By the way, this discussion is off-topic, and
this posting is probably the last one in this thread. LM]
> As clear from the comments above, the probabilistic
> nature of the wavefunction - that physically only exists once the
> measurement is done - is essential for quantum field theory to
> agree with special relativity. LM]
QM makes only predictions about probabilities, it does not
tell us anything about the ontological status of the wave
function.
[Moderator's note: Quantum mechanics tells us quite precisely what is
the ontological status of the wavefunction. The wavefunction is
a mathematical tool to calculate the probabilities of different outcomes
of the experiments. Quantum mechanics also tells us unequivocally
that any other "materialistic" or "realistic" interpretation of the
wavefunction, like those advocated in your posting, is incorrect. LM]
Claims that "the wavefunction only exists once
the measurement is done" are (usually inconsistent)
interpretations of QM, not statements of QM.
[Moderator's note: the probabilistic meaning of the wavefunction is
a postulate and a basic rule of quantum mechanics. It is not only
consistent; it is inevitable and forced upon us. One can develop
different mental pictures how to imagine that the probabilities
follow from the wavefunction; nevertheless, this probabilistic meaning
must be the result. LM]
> [Moderator's note: Some people may be speculating about various
> crazy de Broglie-Bohmian theories, but if they're physicists, they
> should still agree about verified physical results.
There is nothing cracy in Bohmian mechanics. It is a nice and
simple realistic, deterministic theory.
[Moderator's note: The only truly clear problem is that it is wrong.
And incidentally, to say that the Bohmian models are "nice and simple"
can only be understood as a bad joke. These models introduce a lot of
unphysical and inconsequential garbage; even Einstein, who otherwise
disliked the probabilistic interpretation, called the Bohmian models
"unnecessary superstructure". LM]
You may not like it, but it proves that all that anti-realistic quantum
mystery is not forced on us by observation but a deliberate metaphysical
choice.
[Moderator's note: On the contrary. The experiments have proved that
these "realistic" models cannot be consistent with this real Universe as
long as at least elementary artifacts of locality are preserved (which is
probably necessary for Lorentz invariance, which is tested as well).
One may not like the quantum laws of this Universe, but the only thing
she can do about it is to try to move into a different Universe. LM]
> the formalism of quantum field theory makes
> quantum mechanics, locality, causality, and Lorentz invariance
> manifest.
There are QFT variants which use manifest Lorentz invariance,
but there is as well the possibility to use a preferred frame.
[Moderator's note: There cannot exist a hidden variable theory that
is able to violate Bell's inequalities (which is necessary to agree
with observations), but that is also preserving Lorentz invariance
(even manifestly). This statement is the content of Bell's theorem,
as long as you realize that physical non-locality - the ability to
send physical signals superluminally - violates the rules of special
relativity. Special relativity and quantum mechanics are allies, and
they must work together, in order to agree with experiments. See: ]
http://motls.blogspot.com/2004/10/causality-and-entanglement_16.html
> I wonder if one way of getting around this may be to think
> about our universe as being a d-brane in the M-theory sense.
No, there is no such way. The proof of Bell's inequality does
not use any ideas about the way QM or QFT or string theory
describes the entangled two-particle states. It is a very simple
proof which uses only correlations between classical, macroscopic
events (results of measurements, decisions of experimenters)
and very general assumptions about reality:
<f(A,B)> = \int \rho(x) f(A(x,a),B(x,b)) dx
where x describes reality, \rho is a probability distribution
on it, A and B are the observed (macroscopic) results of
the observations, a and b the (also macroscopic) choices
of the experimenters what to measure.
Here realism requires
<f(A,B)> = \int \rho(x) f(A(x,a,b),B(x,a,b)) dx
and Einstein causality leads to the restriction that A should
not depend on b and reverse.
x is in some X which is some set with a probability measure
\rho(x). The nature of X is completely open, there is no
connection between X and our spacetime. No branes no
strings no quantum foam of multiple universes will be able
to improve anything.
Or you decide to define a realistic theory, that means,
a theory which defines some ontology X and some
probability measure on it to explain the observable effects,
then you have to give up Einstein causality on the ontological
level (and have only a restricted Einstein causality for
observables). This is the way of Bohmian mechanics, which
proves that this alternative exists. Or you have to give up
realism. But there is no reason for this except the wish to
immunize SR.
> My qualitative argument is this: Let's follow common conjec-
> tures (eg: Linde and many others) that out of a possible infinite
> set of universes, a given newborn universe may acquire a set of
> permanent values for its fundamental parameters (Co, \hbar, G,
> etc.) out of an effectively randomized and infinite grab-bag of
> possibilities. This implies, for example, that a universe may
> acquire a field-free value for Co anywhere from ~zero to infinite
> velocity. Thus there would be far more (perhaps infinitely
> more) d-branes having Co values far greater than that for any
> given Co in any specific d-brane. Even in a random brane
> arrangement, this would be true for most d-branes happening
> to be 'adjacent' to our universe in a higher dimensional and
> possibly a higher topological embedding.
>
> Now we know also that, while the sub-atomic particles of a d-
> brane are stuck on that brane, and cannot propagate outside of
> it, those particles' wavefunctions can indeed propagate into
> other branes. The consequences of this for particles living in
> other branes are intriguing and being studied by M-theorists.
> But the one I focus on here hinges on the postulate that changes
> in a particle's \psi may always propagate away at the local vel-
> ocity of light. So..
>
> ...When the \psi of entangled particle A changes, that change
> immediately travels out at the velocity of light Co. However, it
> also travels out into other branes b_n, in directions which are
> by definition orthogonal to our universe frame. The local velo-
> city of light Co(b_n) in these branes, is overwhelmingly likely to
> be >>> Co in the original brane containing the entangled pair.
> Thus our \psi will be traveling at far higher Co_b's in other
> branes. Finally, there is always a non-zero probability that
> our propagating \psi-'ripple' will find its way back into our brane
> at the location of particle B (the second member of the pair),
> even if it is now many light years away.
>
> Essentially, the first particle communicates information to the
> second particle, without violating special relativity, by effec-
> tively *short circuiting* the local brane pathways. It still obeys
> local special relativity in each brane it travels through. The
> result then would be virtually indistinguishable from instan-
> taneous propagation, as far as any observers in the particles'
> own universe are concerned.
Sounds interesting but does not change the basic problem.
Or you define some space X with some probability measure
\rho(x) on it, consisting of branes, particles, wave functions on
them in whatever dimensions you like, in this case you have
to reject Einstein causality, or you don't, in this case you reject
realism.
Ilja
John Gonsowski
Oct20-04, 02:52 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>Lubos Motl <motl@feynman.harvard.edu> wrote in message news:<Pine.LNX.4.31.0410161039530.18076-100000@feynman.harvard.edu>...\n> Gene Partlow wrote:\n>\n> > It\'s clear from from the Aspect-type experiments, guided by\n> > Bell\'s work, that our universe is \'nonlocal\', contrary to EPR\'s\n>\n> I\'ve posted an article about entanglement and causality on my blog,\n> http://motls.blogspot.com/\n>\n\nI think you are too harsh on Bohm. I tend to think of two main Bohmian\nideas. One is that superpositions are superpositions of particles at\ndefinite positions. A second is that there is a kind of preexisting\norder governing the possible future paths for particles. M-theory\n(and F-theory) may provide that order.\n\n\n\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Lubos Motl <motl@feynman.harvard.edu> wrote in message news:<Pine.LNX.4.31.0410161039530.18076-100000@feynman.harvard.edu>...
> Gene Partlow wrote:
>
> > It's clear from from the Aspect-type experiments, guided by
> > Bell's work, that our universe is 'nonlocal', contrary to EPR's
>
> I've posted an article about entanglement and causality on my blog,
> http://motls.blogspot.com/
>
I think you are too harsh on Bohm. I tend to think of two main Bohmian
ideas. One is that superpositions are superpositions of particles at
definite positions. A second is that there is a kind of preexisting
order governing the possible future paths for particles. M-theory
(and F-theory) may provide that order.
backdoorstudent
Oct21-04, 02:52 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>Ilja Schmelzer <Ilja.Schmelzer@FernUni-Hagen.de> wrote in message news:<cl33h7\\$lkf\\$1-100000@beech.fernuni-hagen.de>...\n> QM makes only predictions about probabilities, it does not\n> tell us anything about the ontological status of the wave\n> function.\n>\n> [Moderator\'s note: Quantum mechanics tells us quite precisely what is\n> the ontological status of the wavefunction. The wavefunction is\n> a mathematical tool to calculate the probabilities of different outcomes\n> of the experiments. Quantum mechanics also tells us unequivocally\n> that any other "materialistic" or "realistic" interpretation of the\n> wavefunction, like those advocated in your posting, is incorrect. LM]\n\nLM, How can you state this with such absolute certainty when it has no\nbasis in fact? QM does not "tell us unequivocally" that a\n"materialistic" or "realistic" interpretation of the wavefunction is\nincorrect. That is merely a popular opinion. There are plenty of\nrealistic interpretations of the wavefunction that are completely\nconsistent with all experiments.\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Ilja Schmelzer <Ilja.Schmelzer@FernUni-Hagen.de> wrote in message news:<cl33h7$lkf$1-100000@beech.fernuni-hagen.de>...
> QM makes only predictions about probabilities, it does not
> tell us anything about the ontological status of the wave
> function.
>
> [Moderator's note: Quantum mechanics tells us quite precisely what is
> the ontological status of the wavefunction. The wavefunction is
> a mathematical tool to calculate the probabilities of different outcomes
> of the experiments. Quantum mechanics also tells us unequivocally
> that any other "materialistic" or "realistic" interpretation of the
> wavefunction, like those advocated in your posting, is incorrect. LM]
LM, How can you state this with such absolute certainty when it has no
basis in fact? QM does not "tell us unequivocally" that a
"materialistic" or "realistic" interpretation of the wavefunction is
incorrect. That is merely a popular opinion. There are plenty of
realistic interpretations of the wavefunction that are completely
consistent with all experiments.
backdoorstudent
Oct22-04, 02:24 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>Ilja Schmelzer <Ilja.Schmelzer@FernUni-Hagen.de> wrote in message news:<cl33h7\\$lkf\\$1-100000@beech.fernuni-hagen.de>...\n> You may not like it, but it proves that all that anti-realistic quantum\n> mystery is not forced on us by observation but a deliberate metaphysical\n> choice.\n>\n> [Moderator\'s note: On the contrary. The experiments have proved that\n> these "realistic" models cannot be consistent with this real Universe as\n> long as at least elementary artifacts of locality are preserved (which is\n> probably necessary for Lorentz invariance, which is tested as well).\n> One may not like the quantum laws of this Universe, but the only thing\n> she can do about it is to try to move into a different Universe. LM]\n\nWhat do you mean by "elementary artifacts of locality"?\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Ilja Schmelzer <Ilja.Schmelzer@FernUni-Hagen.de> wrote in message news:<cl33h7$lkf$1-100000@beech.fernuni-hagen.de>...
> You may not like it, but it proves that all that anti-realistic quantum
> mystery is not forced on us by observation but a deliberate metaphysical
> choice.
>
> [Moderator's note: On the contrary. The experiments have proved that
> these "realistic" models cannot be consistent with this real Universe as
> long as at least elementary artifacts of locality are preserved (which is
> probably necessary for Lorentz invariance, which is tested as well).
> One may not like the quantum laws of this Universe, but the only thing
> she can do about it is to try to move into a different Universe. LM]
What do you mean by "elementary artifacts of locality"?
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