very_cryptic@hotmail.com
Oct24-04, 09:04 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>\n\nIs spacetime an emergent property of an underlying theory which is\nfundamentally aspatial? Dualities such as the adS/CFT duality and\nT-dualities tell us that the SAME model can be expressed as a quantum\nfield theory in two utterly different spacetime backgrounds.\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>Is spacetime an emergent property of an underlying theory which is
fundamentally aspatial? Dualities such as the adS/CFT duality and
T-dualities tell us that the SAME model can be expressed as a quantum
field theory in two utterly different spacetime backgrounds.
Jochen Fromm
Oct25-04, 08:10 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>\n\nProbably yes.\nSpace-Time obviously emerged with or at the Big Bang, or\nin other words, the Big Bang is closely related to the\nemergence of space-time. How exactly is still a matter of\ndiscussion. Lee Smolin has argued in "The Life of the Cosmos",\nthat the "Big Bang" at the beginning is connected to the "Big\nCrunch" in black holes at the end, and that black holes cause\nand encapsulate new big bangs.\n\nOpen questions are\n\n* if spacetime emerged only once in a single moment or\nif it is still "emerging". In case of the latter, which is\na bit more probable, what is the basic process behind\nthe emergence of space and time ? Does it involve\nsome form of merging and splitting of elementary\nstructures (a Big Bang vs. Big Crunch on many scales) ?\n\n* if spacetime is an emergent property (for instance\na property of the instable space-time foam near\nthe planck scale), how does it emerge from a\ndeeper level ? Are particles emergent properties, too ?\nStanford University Professor Robert B. Laughlin\nsaid in his Nobel Lecture: "One of the things an\nemergent phenomenon can do is create new particles", see\nhttp://nobelprize.org/physics/laureates/1998/laughlin-lecture.pdf\n\n* How does quantum theory arise together with spatial\nproperties of space-time ?\n\nI personally think the answers have something to do\nwith evolution: replication and variation of elementary\nspace-time structures in a self-reproducing universe...\nThe emergence of spacetime is a hot topic, since it is\nconnected to "quantum gravity", the holy grail of theoretical\nphysics at the time. Some recent papers about the topic are:\n\nQuantum Theory from Quantum Gravity\nFotini Markopoulou, Lee Smolin\nhttp://www.arXiv.org/abs/gr-qc/0311059\n\nEmergence of a 4D World from Causal Quantum Gravity\nJan Ambjorn, Jerzy Jurkiewicz, Renate Loll\nhttp://www.arXiv.org/abs/hep-th/0404156\n\nAmbjorn, Jurkiewicz, and Loll are from the Niels Bohr Institute,\nCopenhagen (Denmark), Jagellonian University, Krakow (Poland),\nand Spinoza Institute, Utrecht (The Netherlands), respectively.\nTheir approach is based on dynamical triangulations with two\nconditions/constraints\n* nothing can travel faster than light\n* causality must be preserved\n\nA good description can be found in this Nature online article:\n"How to build the Universe: Including cause-and-effect in equations\nproduces 4-dimensional space-time"\nhttp://www.nature.com/news/2004/041004/full/041004-17.html\n\nThere was also a discussion here:\nhttp://physicsforums.com/showthread.php?t=25102\nand here:\nhttp://www.phys.lsu.edu/mog/mog19/node12.html\n\nThe two following articles about spacetime and Quantum\nGravity will appear in "Spacetime 100 Years Later",\nJorge Pullin and Richard Price (Editors), World Year of\nPhysics Special Issue of "New Journal of Physics", 2005\n\nGravity and the Quantum (Abhay Ashtekar)\nThe goal of this article is to present a broad perspective\non quantum gravity for non-experts. After a historical\nintroduction, key physical problems of quantum gravity are\nillustrated. While there are a number of interesting and\ninsightful approaches to address these issues, over the\npast two decades sustained progress has primarily occurred\nin two programs: string theory and loop quantum gravity.\nThe first program is described in Horowitz\'s contribution\nwhile my article will focus on the second. The emphasis is\non underlying ideas, conceptual issues and overall status\nof the program rather than mathematical details and associated\ntechnical subtleties.\nhttp://arxiv.org/abs/gr-qc/0410054\n\nSpacetime in String Theory (Gary T. Horowitz)\nWe give a brief overview of the nature of spacetime\nemerging from string theory. This is radically different\nfrom the familiar spacetime of Einstein\'s relativity. At\na perturbative level, the spacetime metric appears as\n"coupling constants" in a two dimensional quantum field\ntheory. Nonperturbatively (with certain boundary conditions),\nspacetime is not fundamental but must be reconstructed from\na holographic, dual theory.\nhttp://arxiv.org/abs/gr-qc/0410049\n\n\nBest Regards,\nJochen Fromm\n\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>Probably yes.
Space-Time obviously emerged with or at the Big Bang, or
in other words, the Big Bang is closely related to the
emergence of space-time. How exactly is still a matter of
discussion. Lee Smolin has argued in "The Life of the Cosmos",
that the "Big Bang" at the beginning is connected to the "Big
Crunch" in black holes at the end, and that black holes cause
and encapsulate new big bangs.
Open questions are
* if spacetime emerged only once in a single moment or
if it is still "emerging". In case of the latter, which is
a bit more probable, what is the basic process behind
the emergence of space and time ? Does it involve
some form of merging and splitting of elementary
structures (a Big Bang vs. Big Crunch on many scales) ?
* if spacetime is an emergent property (for instance
a property of the instable space-time foam near
the planck scale), how does it emerge from a
deeper level ? Are particles emergent properties, too ?
Stanford University Professor Robert B. Laughlin
said in his Nobel Lecture: "One of the things an
emergent phenomenon can do is create new particles", see
http://nobelprize.org/physics/laureates/1998/laughlin-lecture.pdf
* How does quantum theory arise together with spatial
properties of space-time ?
I personally think the answers have something to do
with evolution: replication and variation of elementary
space-time structures in a self-reproducing universe...
The emergence of spacetime is a hot topic, since it is
connected to "quantum gravity", the holy grail of theoretical
physics at the time. Some recent papers about the topic are:
Quantum Theory from Quantum Gravity
Fotini Markopoulou, Lee Smolin
http://www.arXiv.org/abs/http://www.arxiv.org/abs/gr-qc/0311059
Emergence of a 4D World from Causal Quantum Gravity
Jan Ambjorn, Jerzy Jurkiewicz, Renate Loll
http://www.arXiv.org/abs/http://www.arxiv.org/abs/hep-th/0404156
Ambjorn, Jurkiewicz, and Loll are from the Niels Bohr Institute,
Copenhagen (Denmark), Jagellonian University, Krakow (Poland),
and Spinoza Institute, Utrecht (The Netherlands), respectively.
Their approach is based on dynamical triangulations with two
conditions/constraints
* nothing can travel faster than light
* causality must be preserved
A good description can be found in this Nature online article:
"How to build the Universe: Including cause-and-effect in equations
produces 4-dimensional space-time"
http://www.nature.com/news/2004/041004/full/041004-17.html
There was also a discussion here:
http://physicsforums.com/showthread.php?t=25102
and here:
http://www.phys.lsu.edu/mog/mog19/node12.html
The two following articles about spacetime and Quantum
Gravity will appear in "Spacetime 100 Years Later",
Jorge Pullin and Richard Price (Editors), World Year of
Physics Special Issue of "New Journal of Physics", 2005
Gravity and the Quantum (Abhay Ashtekar)
The goal of this article is to present a broad perspective
on quantum gravity for non-experts. After a historical
introduction, key physical problems of quantum gravity are
illustrated. While there are a number of interesting and
insightful approaches to address these issues, over the
past two decades sustained progress has primarily occurred
in two programs: string theory and loop quantum gravity.
The first program is described in Horowitz's contribution
while my article will focus on the second. The emphasis is
on underlying ideas, conceptual issues and overall status
of the program rather than mathematical details and associated
technical subtleties.
http://arxiv.org/abs/http://www.arxiv.org/abs/gr-qc/0410054
Spacetime in String Theory (Gary T. Horowitz)
We give a brief overview of the nature of spacetime
emerging from string theory. This is radically different
from the familiar spacetime of Einstein's relativity. At
a perturbative level, the spacetime metric appears as
"coupling constants" in a two dimensional quantum field
theory. Nonperturbatively (with certain boundary conditions),
spacetime is not fundamental but must be reconstructed from
a holographic, dual theory.
http://arxiv.org/abs/http://www.arxiv.org/abs/gr-qc/0410049
Best Regards,
Jochen Fromm
very_cryptic@hotmail.com
Nov2-04, 12:38 PM
<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>\n\nI\'ve got an idea which is somewhat like Julian Barbour\'s idea except\nthat I propose to localize ourselves in space as well.\n\nBasically, the idea is as follows: It\'s the state of low entropy which\nCREATES spacetime and the laws of physics, which would not exist\notherwise.\n\nWe know from local quantum physics about the idea of local nets of\nalgebras and a presheaf of states (presheaf because of quantum\nentanglement). But how do we know the past exists? Only through\nmemories and our perception through our senses that there are other\nrecords which all show some consistency. How do we know time flows?\nIt\'s an illusion created by our neurological architecture which tries\nto model motion. This again depends on a state of low entropy. Now\nlet\'s go on to space. How do we know other places other than here\nexist? Only though our senses, but can\'t the world conspire to create\nsuch an illusion? We can\'t really know what happens outside here.\nLocality and spacelike commutativity rules that out. How can we predict\nthe future? We can\'t, because how can we be sure something unexpected\nfrom outside our lightcone won\'t come and completely mess things up.\nHow can we be sure the universe obeys the laws of physics? Once again,\nwe have to rely on the correlations between memories and perception. Is\nthere any reason why the universe can\'t conspire to create such an\nillusion? Well not even necessarily the universe but just the here and\nnow.\n\nNow if the universe, or for that matter, just the here and now, which\nis the only thing we can be sure about (if even that) is in a state of\nmaximum entropy? Then there would be no correlations, and for that\nmatter, no brain and without any correlations, there would be no past,\nno future, no flow of time and no space and no laws of physics.\n\nHow about quantum entanglements with places other than here? Since all\nwe know about is the here and now, we can use Occam\'s razor to\neliminate that and just work with pure states associated with the\nalgebra associated with the here and now.\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>I've got an idea which is somewhat like Julian Barbour's idea except
that I propose to localize ourselves in space as well.
Basically, the idea is as follows: It's the state of low entropy which
CREATES spacetime and the laws of physics, which would not exist
otherwise.
We know from local quantum physics about the idea of local nets of
algebras and a presheaf of states (presheaf because of quantum
entanglement). But how do we know the past exists? Only through
memories and our perception through our senses that there are other
records which all show some consistency. How do we know time flows?
It's an illusion created by our neurological architecture which tries
to model motion. This again depends on a state of low entropy. Now
let's go on to space. How do we know other places other than here
exist? Only though our senses, but can't the world conspire to create
such an illusion? We can't really know what happens outside here.
Locality and spacelike commutativity rules that out. How can we predict
the future? We can't, because how can we be sure something unexpected
from outside our lightcone won't come and completely mess things up.
How can we be sure the universe obeys the laws of physics? Once again,
we have to rely on the correlations between memories and perception. Is
there any reason why the universe can't conspire to create such an
illusion? Well not even necessarily the universe but just the here and
now.
Now if the universe, or for that matter, just the here and now, which
is the only thing we can be sure about (if even that) is in a state of
maximum entropy? Then there would be no correlations, and for that
matter, no brain and without any correlations, there would be no past,
no future, no flow of time and no space and no laws of physics.
How about quantum entanglements with places other than here? Since all
we know about is the here and now, we can use Occam's razor to
eliminate that and just work with pure states associated with the
algebra associated with the here and now.
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