<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>"ksh95" <ksh95@yahoo.com> schrieb im Newsbeitrag\nnews:38a3ceaf.0406020519.6aec9c7@post ing.google.com...\n\n> I think Al is asserting that spiral staircases fall differently than\n> good ole\' straight staircases.\n\nThis was discussed here years ago already, but since it comes up repeatedly\nit might be worth reemphasizing it:\n\nIf left-handed screws fell differently than right-handed screws this would\nbe a rather weird violation of locality on scales far, far away (even\nassuming that the screws are of melecular size) from any scales on which we\nmight speculate about non-local effects due to some theory of quantum\ngravity or something similar.\n\nThis has nothing to do with what flavor of gravitational theory one is\nusing. The Einstein-Hilbert action, the Palatini action, teleparallel\nformulations, theories of torsion gravity, etc are all local. Their\nequations of motion pertain to every point of spacetime seperately, e.g.\n\nG(x) = T(x) for all x in your manifold\n\nThere are indeed some non-local effects in theories of non-commuative fields\nand in effective field theories of strings, for instance, but\n\n1) This non-locality is expected to be at roughly the Planck scale.\n\n2) Even if it were of the scale of Angstroms (which it is not!), it is\npretty inconceivable how it could scan space in such a way so as to\ndetermine the handedness of macroscopic objects and pull them to the ground\naccording to that result.\n\n\nHence it is wrong to say that theory is undecided about the result\nof the "Parity-Eotvos" experiment (if, as you say, this concerns macroscopic\nhandedness instead of intrinsic fundamental spin). If such an experiment\nyielded a non-null result physics as we know it would be completely\noverthrown.\n\nOn the other hand, I would be interested in learning more about experiments\nthat might check for _torsion_ and hence an EP violation of stuff carrying\nelementary spin:\n\nhttp://golem.ph.utexas.edu/string/archives/000310.html .\n\nBTW, in the context of a current sci.physics.strings thread\n\nhttp://groups.google.de/groups?selm=c9agts%24qgm%2403%241-100000%40news.t-online.com\n\nI have taken the time to collect some links to experiments in the spirit of\nUncle Al\'s experiments that try to discover "new physics" without using\nhigh-energy particle accelerators. (There seems to be a problem with the\nnewsserver at Harvard and the post does not seem to have propagated to other\nnewsservers at the time I am writing this.):\n\nHere is a set of slides by Pisin Chen from SLAC discussing some implications\nof possible astrophysical observations for new physics:\n\nhttp://www-conf.slac.stanford.edu/orion/PAPERS/A09.PDF\n\nand\n\nhttp://www.aapps.org/archive/bulletin/vol13/13_1/13_1_p03p10.pdf\n\n\nPeople are looking in particular at the following effects:\n\n1) Ultra High Energy Cosmic Rays\n2) Lorentz violation on small scales\n3) Detection of dark matter\n4) Search for additional spatial dimensions and violations of the\nequivalence\nprinciple\n5) Spacetime granularity\n\n\nI\'ll give some links and comments for all these 5 points (but this is of\ncourse far from being a comprehensive review):\n\n1) Ultra High Energy Cosmic Rays should on theoretical grounds be cut off at\n5x10^19 eV, the so-called Greisen-Zatzepin-Kuzmin (GZK) limit, due to the\nabsorbtion of highly energetic rays by the cosmic microwave background:\n\nhttp://encyclopedia.thefreedictionary.com/GZK%20limit .\n\nBut at least one experiment has claimed to have seen particles boyond the\nGZK\nlimit.\n\nRecently Edward Witten commented on this experiment in the thread\n\nhttp://groups.google.de/groups?selm=33023f5e.0405111526.6a07f7d0-100000%40posting.google.com\n\nwhere he said:\n>>>\nalistair <alistair@goforit64.fsnet.co.uk> wrote in message\nnews:<861c1b21.0404291048.2658d8c4-100000@posting.google.com>...\n\n> What do the string theories have to say about something like the GZK\n> paradox where ultra high energy cosmic ray protons reach the Earth when\n> they should have been absorbed by the cosmic microwave background?\n\nIt is not clear at the moment that there is anything to explain.\nOne of the two main experimental groups (AGASA) reported\nas of over a year ago that their high energy data are in accord\nwith the expected GZK cutoff. The other group continues\nto report a discrepancy. We\'ll see what happens as data improve.\nEdward Witten\n<<<\n\n\n2) People are apparently looking for violation of Lorentz invariance at\nsmall\nscales/large energies.\n\nhttp://qom.physik.hu-berlin.de/prl_91_020401_2003.pdf\nhttp://cfa-www.harvard.edu/Walsworth/Activities/posters/lliposter.pdf\n\nFrom some theories of quantum gravity one might expect such effects,\nprobably\nnot from string theory.\n\n\n\n3) Nature of dark matter.\n\nSeveral people are trying to determine the presence and maybe the nature of\ndark matter.\n\nFor instance the DAMA collaboration\n\nhttp://www.lngs.infn.it/lngs/htexts/dama/dama39.html\n\nand the UK Dark Matter collaboration\n\nhttp://hepwww.rl.ac.uk//UKDMC/ukdmc.html\n\nas briefly summarized in this message:\n\nhttp://groups.google.de/groups?selm=b848qo%24epr%241%40glue.ucr.edu\n\nOf course the true nature of dark matter may be a very important clue for\nhow\nthe true theory of quantum gravity looks like, but current experiments are\nof\ncourse very far from saying anything about this.\n\n\n\n4) Search for additional spatial dimenions and violations of the equivalence\nprinciple\n\nThere are potentially very interesting high-precision measurements of the\nequivalence principle, most notably by the "EotWash" group\n\nhttp://www.npl.washington.edu/eotwash/ .\n\nVariation of the usual 1/r^2 force law of gravity on small scales could be\nrelated to extra dimensions and or torsion, for instance.\n\nBTW, what does string theory say about phenomenogically observable torsion?\nThe Kalb-Ramond field enters the background equations of motion at the same\norder (lowest order in \\alpha\') as the Einstein-Hilber term, and a\nnon-vanishing B-field corresponds to a torsion effect with torsion equal to\n\\pm dB. If we say that string theory "predicts gravity" shouldn\'t we also\nsay\nthat it predicts torsion?\n\nI have a brief note and some literature on this question at the String\nCoffee\nTable:\n\nhttp://golem.ph.utexas.edu/string/archives/000310.html\n\n\n\n\n5) Spacetime granularity\n\nFrom quantum gravity some people expect that on extremely small scales\nspacetime will show some sort of foamy structure, maybe being topologically\nnon-trivial. An old idea by Percival and collaborators is that atom\ninterferometry, e.g. the 2-slit experiment with heavy stuff such as\nBuckminster Fullerenes (Nature Vol. 401, No. 6754, p. 680 (1999).) as done\nby Zeilinger\'s group (http://www.edge.org/3rd_culture/bios/zeilinger.html), may\nbe sensitive to such a spacetime grabularity.\n\nI had mentioned that in the past from time to time\n\nhttp://groups.google.de/groups?selm=9a4m0g%24bvq1%40rs04.hrz.uni-essen.de\nhttp://groups.google.de/groups?selm=3E5A1BAC.F2755C1B%40uni-essen.de\n\ngiving some references.\n\nI am not sure what string theory really says about "quantum spacetime foam"\nat small scales.\n\nWhen we discussed Smolin\'s paper http://arxiv.org/abs/hep-th/0303185 it was\nargued that string theory (on Minkowski space, say) predicts smooth\nspacetime down to all scales. I argued in\n\nhttp://groups.google.de/groups?selm=3E64A7EC.D4DC1E00%40uni-essen.de\nhttp://groups.google.de/groups?selm=3E7B059B.87CC7802%40uni-essen.de\n\nbased on the discussion in\n\nFedele Lizzi anmd Richard Szabo,\nDuality Symmetries and Noncommutative Geometry of String Spacetimes,\nhep-th/9707202\n\nthat this is not quite correct, since as you try to probe the smooth\nbackground with highly energetic strings you will eventually see stringy\neffects and not be able to resolve the smoothness of the classical\nbackground\nat all, so that effectively it is not smooth on small scales.\n\nSo might stringy physics effect the phase of atoms/molecues used in matter\ninterferometry ever so slightly?\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>"ksh95" <ksh95@yahoo.com> schrieb im Newsbeitrag
news:38a3ceaf.0406020519.6aec9c7@posting.google.co m...
> I think Al is asserting that spiral staircases fall differently than
> good ole' straight staircases.
This was discussed here years ago already, but since it comes up repeatedly
it might be worth reemphasizing it:
If left-handed screws fell differently than right-handed screws this would
be a rather weird violation of locality on scales far, far away (even
assuming that the screws are of melecular size) from any scales on which we
might speculate about non-local effects due to some theory of quantum
gravity or something similar.
This has nothing to do with what flavor of gravitational theory one is
using. The Einstein-Hilbert action, the Palatini action, teleparallel
formulations, theories of torsion gravity, etc are all local. Their
equations of motion pertain to every point of spacetime seperately, e.g.
G(x) = T(x) for all x in your manifold
There are indeed some non-local effects in theories of non-commuative fields
and in effective field theories of strings, for instance, but
1) This non-locality is expected to be at roughly the Planck scale.
2) Even if it were of the scale of Angstroms (which it is not!), it is
pretty inconceivable how it could scan space in such a way so as to
determine the handedness of macroscopic objects and pull them to the ground
according to that result.
Hence it is wrong to say that theory is undecided about the result
of the "Parity-Eotvos" experiment (if, as you say, this concerns macroscopic
handedness instead of intrinsic fundamental spin). If such an experiment
yielded a non-null result physics as we know it would be completely
overthrown.
On the other hand, I would be interested in learning more about experiments
that might check for _torsion_ and hence an EP violation of stuff carrying
elementary spin:
http://golem.ph.utexas.edu/string/archives/000310.html .
BTW, in the context of a current sci.physics.strings thread
http://groups.google.de/groups?selm=c9agts%24qgm%2403%241-100000%40news.t-online.com
I have taken the time to collect some links to experiments in the spirit of
Uncle Al's experiments that try to discover "new physics" without using
high-energy particle accelerators. (There seems to be a problem with the
newsserver at Harvard and the post does not seem to have propagated to other
newsservers at the time I am writing this.):
Here is a set of slides by Pisin Chen from SLAC discussing some implications
of possible astrophysical observations for new physics:
http://www-conf.slac.stanford.edu/orion/PAPERS/A09.PDF
and
http://www.aapps.org/archive/bulletin/vol13/13_1/13_1_p03p10.pdf
People are looking in particular at the following effects:
1) Ultra High Energy Cosmic Rays
2) Lorentz violation on small scales
3) Detection of dark matter
4) Search for additional spatial dimensions and violations of the
equivalence
principle
5) Spacetime granularity
I'll give some links and comments for all these 5 points (but this is of
course far from being a comprehensive review):
1) Ultra High Energy Cosmic Rays should on theoretical grounds be cut off at
5x10^19 eV, the so-called Greisen-Zatzepin-Kuzmin (GZK) limit, due to the
absorbtion of highly energetic rays by the cosmic microwave background:
http://encyclopedia.thefreedictionary.com/GZK%20limit .
But at least one experiment has claimed to have seen particles boyond the
GZK
limit.
Recently Edward Witten commented on this experiment in the thread
http://groups.google.de/groups?selm=33023f5e.0405111526.6a07f7d0-100000%40posting.google.com
where he said:
>>>
alistair <alistair@goforit64.fsnet.co.uk> wrote in message
news:<861c1b21.0404291048.2658d8c4-100000@posting.google.com>...
> What do the string theories have to say about something like the GZK
> paradox where ultra high energy cosmic ray protons reach the Earth when
> they should have been absorbed by the cosmic microwave background?
It is not clear at the moment that there is anything to explain.
One of the two main experimental groups (AGASA) reported
as of over a year ago that their high energy data are in accord
with the expected GZK cutoff. The other group continues
to report a discrepancy. We'll see what happens as data improve.
Edward Witten
<<<
2) People are apparently looking for violation of Lorentz invariance at
small
scales/large energies.
http://qom.physik.hu-berlin.de/prl_91_020401_2003.pdf
http://cfa-www.harvard.edu/Walsworth/Activities/posters/lliposter.pdf
From some theories of quantum gravity one might expect such effects,
probably
not from string theory.
3) Nature of dark matter.
Several people are trying to determine the presence and maybe the nature of
dark matter.
For instance the DAMA collaboration
http://www.lngs.infn.it/lngs/htexts/dama/dama39.html
and the UK Dark Matter collaboration
http://hepwww.rl.ac.uk//UKDMC/ukdmc.html
as briefly summarized in this message:
http://groups.google.de/groups?selm=b848qo%24epr%241%40glue.ucr.edu
Of course the true nature of dark matter may be a very important clue for
how
the true theory of quantum gravity looks like, but current experiments are
of
course very far from saying anything about this.
4) Search for additional spatial dimenions and violations of the equivalence
principle
There are potentially very interesting high-precision measurements of the
equivalence principle, most notably by the "EotWash" group
http://www.npl.washington.edu/eotwash/ .
Variation of the usual 1/r^2 force law of gravity on small scales could be
related to extra dimensions and or torsion, for instance.
BTW, what does string theory say about phenomenogically observable torsion?
The Kalb-Ramond field enters the background equations of motion at the same
order (lowest order in \alpha') as the Einstein-Hilber term, and a
non-vanishing B-field corresponds to a torsion effect with torsion equal to
\pm dB. If we say that string theory "predicts gravity" shouldn't we also
say
that it predicts torsion?
I have a brief note and some literature on this question at the String
Coffee
Table:
http://golem.ph.utexas.edu/string/archives/000310.html
5) Spacetime granularity
From quantum gravity some people expect that on extremely small scales
spacetime will show some sort of foamy structure, maybe being topologically
non-trivial. An old idea by Percival and collaborators is that atom
interferometry, e.g. the 2-slit experiment with heavy stuff such as
Buckminster Fullerenes (Nature Vol. 401, No. 6754, p. 680 (1999).) as done
by Zeilinger's group (http://www.edge.org/3rd_culture/bios/zeilinger.html), may
be sensitive to such a spacetime grabularity.
I had mentioned that in the past from time to time
http://groups.google.de/groups?selm=9a4m0g%24bvq1%40rs04.hrz.uni-essen.de
http://groups.google.de/groups?selm=3E5A1BAC.F2755C1B%40uni-essen.de
giving some references.
I am not sure what string theory really says about "quantum spacetime foam"
at small scales.
When we discussed Smolin's paper http://arxiv.org/abs/http://www.arxiv.org/abs/hep-th/0303185 it was
argued that string theory (on Minkowski space, say) predicts smooth
spacetime down to all scales. I argued in
http://groups.google.de/groups?selm=3E64A7EC.D4DC1E00%40uni-essen.de
http://groups.google.de/groups?selm=3E7B059B.87CC7802%40uni-essen.de
based on the discussion in
Fedele Lizzi anmd Richard Szabo,
Duality Symmetries and Noncommutative Geometry of String Spacetimes,
http://www.arxiv.org/abs/hep-th/9707202
that this is not quite correct, since as you try to probe the smooth
background with highly energetic strings you will eventually see stringy
effects and not be able to resolve the smoothness of the classical
background
at all, so that effectively it is not smooth on small scales.
So might stringy physics effect the phase of atoms/molecues used in matter
interferometry ever so slightly?