Science > Physics > Indian scientist makes first predictions from string theory
| Topic: |
Science > Physics |
| User: |
"Habshi" |
| Date: |
07 Mar 2004 11:25:41 AM |
| Object: |
Indian scientist makes first predictions from string theory |
Its in danger of unravelling .
excerpt economist.com
In a paper just published in Nuclear Physics B, Samir Mathur and his
colleagues at Ohio State University seem to have solved the paradox
using string theory, which is the best available attempt to reconcile
relativity and quantum mechanics. This theory, which postulates that
everything in the universe is a consequence of tiny strings
oscillating in ten dimensions, was thought to have observable
consequences only at very small scales—as much smaller than atoms as
atoms are smaller than the solar system. Dr Mathur showed, however,
that at high densities of matter, such as those within a black hole,
the effects attributable to strings can grow to large sizes.
According to Dr Mathur, the interior of a black hole can be thought of
as a ball of strings. This ball modulates the Hawking radiation in a
way that reflects the arrangement of the strings inside the hole. So,
in effect, it acts as a repository of the information carried by
things that have fallen into the hole. Thus, as quantum mechanics
requires, no information is destroyed.
Besides resolving the information paradox, this theory has the added
benefit—at least in the special cases that Dr Mathur has been able to
work out exactly—of getting rid of the “singularity” that had been
thought to lie at the centre of every black hole. A singularity is a
mathematical anomaly where physical theories such as general
relativity break down because quantities that should be finite diverge
to infinity. This means that physicists are unable, even in principle,
to explain what is actually happening there. It would therefore be
quite a boon if Dr Mathur is correct, and singularities do not
actually exist.
His result also has a bearing on wider cosmological issues. The early
universe would have had a density similar to a black hole, and so the
“string-ball” theory would have applied there, too. Though Dr Mathur
is cautious on the matter, his theory might supply an alternative
explanation about why—when viewed on the grandest scales—the universe
appears remarkably uniform.
At the moment, this uniformity is put down to a phenomenon known as
cosmic inflation, in which the universe is supposed to have expanded
rapidly when it was very young. That expansion would have “locked in”
the universe's initial uniform state by stopping local concentrations
of matter from forming. Tying the early universe together with strings
might provide an alternative explanation for cosmic uniformity.
String theory is often criticised because it is abstract and thus hard
to compare with reality. But although no one can yet see a black hole
close up, and thus test Dr Mathur's ideas for real, the fact that
string theory seems able, in this case, to resolve long-standing
inconsistencies between general relativity and quantum mechanics is a
big point in its favour.
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| User: "Uncle Al" |
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| Title: Re: Indian scientist makes first predictions from string theory |
07 Mar 2004 12:50:06 PM |
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Habshi wrote:
Its in danger of unravelling .
excerpt economist.com
In a paper just published in Nuclear Physics B, Samir Mathur and his
colleagues at Ohio State University
What part of India is that?
seem to have solved the paradox
using string theory, which is the best available attempt to reconcile
relativity and quantum mechanics.
[snip]
Relativity and quantum mechanics cannot be resolved,
classical physics: h=zero G=G c=infinity
quantum mechanics: h=h G=zero c=infinity
general relativity: h=zero G=G c=c
A different and more inclusive theory must be wrought.
Dr Mathur showed, however,
that at high densities of matter, such as those within a black hole,
the effects attributable to strings can grow to large sizes.
Nothing within a black hole event horizon can be externally observed.
According to Dr Mathur, the interior of a black hole can be thought of
as a ball of strings. This ball modulates the Hawking radiation in a
way that reflects the arrangement of the strings inside the hole. So,
in effect, it acts as a repository of the information carried by
things that have fallen into the hole. Thus, as quantum mechanics
requires, no information is destroyed.
Kewl. Predict an observable.
Besides resolving the information paradox, this theory has the added
benefit—at least in the special cases that Dr Mathur has been able to
work out exactly—of getting rid of the “singularity” that had been
thought to lie at the centre of every black hole.
"lay." Still needs an observable.
String theory is often criticised because it is abstract and thus hard
to compare with reality. But although no one can yet see a black hole
close up, and thus test Dr Mathur's ideas for real, the fact that
string theory seems able, in this case, to resolve long-standing
inconsistencies between general relativity and quantum mechanics is a
big point in its favour.
pssst.
--
Uncle Al
http://www.mazepath.com/uncleal/qz.pdf
http://www.mazepath.com/uncleal/eotvos.htm
(Do something naughty to physics)
.
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| User: "hanson" |
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| Title: Re: Indian scientist makes first predictions from string theory |
07 Mar 2004 02:30:26 PM |
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"Uncle Al" <UncleAl0@hate.spam.net> wrote in message
news:404B6EDE.B013D96@hate.spam.net...
Habshi wrote:
Its in danger of unravelling .
excerpt economist.com
In a paper just published in Nuclear Physics B, Samir Mathur and his
colleagues at Ohio State University
What part of India is that?
seem to have solved the paradox
using string theory, which is the best available attempt to reconcile
relativity and quantum mechanics.
[snip]
Relativity and quantum mechanics cannot be resolved,
classical physics: h=zero G=G c=infinity
quantum mechanics: h=h G=zero c=infinity
general relativity: h=zero G=G c=c
A different and more inclusive theory must be wrought.
*******
Yes, .... Any TOE, if discrete and self-similar, with
h=h G=G c=c N_A = N_A will do, but NOT
in form of a single equation: solution = f(h,G,c,N_A)
hanson
*******
Dr Mathur showed, however,
that at high densities of matter, such as those within a black hole,
the effects attributable to strings can grow to large sizes.
Nothing within a black hole event horizon can be externally observed.
According to Dr Mathur, the interior of a black hole can be thought of
as a ball of strings. This ball modulates the Hawking radiation in a
way that reflects the arrangement of the strings inside the hole. So,
in effect, it acts as a repository of the information carried by
things that have fallen into the hole. Thus, as quantum mechanics
requires, no information is destroyed.
Kewl. Predict an observable.
Besides resolving the information paradox, this theory has the added
benefit-at least in the special cases that Dr Mathur has been able to
work out exactly-of getting rid of the "singularity" that had been
thought to lie at the centre of every black hole.
"lay." Still needs an observable.
String theory is often criticised because it is abstract and thus hard
to compare with reality. But although no one can yet see a black hole
close up, and thus test Dr Mathur's ideas for real, the fact that
string theory seems able, in this case, to resolve long-standing
inconsistencies between general relativity and quantum mechanics is a
big point in its favour.
pssst.
--
Uncle Al
http://www.mazepath.com/uncleal/qz.pdf
http://www.mazepath.com/uncleal/eotvos.htm
(Do something naughty to physics)
.
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| User: "Alfred Einstead" |
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| Title: Re: Indian scientist makes first predictions from string theory |
07 Mar 2004 06:11:07 PM |
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Uncle Al <UncleAl0@hate.spam.net> wrote:
Relativity and quantum mechanics cannot be resolved,
classical physics: h=zero G=G c=infinity
quantum mechanics: h=h G=zero c=infinity
general relativity: h=zero G=G c=c
A different and more inclusive theory must be wrought.
Well, when you quantize the metric, that means the light cone
is smeared out and causality, itself, becomes state-dependent.
It's specifically the light cones where the singular nature of
quantum field theory comes from in the first place (the
propagators, in particular, all go singular on the light cone).
Likewise, it's the issue of temporal ordering and causality
where everything hangs up when trying to extend the apparatus
of (say) the canonical approach to non-globally hyperbolic
manifolds.
Likewise, in classical electromagnetism, it's the light cone
structure created by adding the constitutive relations
(D = epsilon_0 E; B = mu_0 H) to the global Maxwell equations
(dF = 0; dH = J) that creates the singularity in the stress
tensor and force law.
The irreconcilabilities all seem to come down to that same issue.
The light cone is too singular.
But when you smear it, that means you have such things as
"light cone tunnelling", where causality can be violated near the
light cone, itself (i.e., at very small scales or high energies
or high speeds).
Since your article is really a pretext to your pet issue (testing
the equivalence principle and trying to find a loophole in it),
you'll find one of the sections in "Geometry and Theoretical
Physics" (J. Debrus, A.C. Hirshfeld eds.) Springer-Verlag 1991 to
be of interest: particularly, "Two Lectures on Fermions and
Gravity", W. Hehl, J. Lemke, and E.W. Mielke; which (among other
things) discusses a number of experiments done in recent years
testing the effects of gravity in the quantum theoretical domain.
(e.g., the COW experiement, Bronse-Wroblewski experiment, etc.);
as well as discussing the question of whether the equivalence
principle is valid for quantum particles.
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| User: "Jeff Relf" |
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| Title: The singularity is virtual, not physical. |
07 Mar 2004 01:08:18 PM |
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Hi Habshi, You cite a piece from _ The Economist _ :
" Tying the early universe together with strings
might provide an alternative explanation for
cosmic uniformity. ".
The singularity at the start of the big bang
is based on our prejudiced notions about what constitutes
a " proper " scale of heat, time and space.
So the singularity is virtual, not physical.
It changes when you modify those prejudiced notions.
And without those notions, it completely disappears.
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