Re: [obm-l] riemann

["Nicolau C. Saldanha" <nicolau@xxxxxxxxxxxxxxxxxxxxx>]

On Wed, Apr 16, 2003 at 06:56:22PM -0300, gabriel wrote:
> Caro Nicolau,
> So nao entendi uma coisa; porque estes preprints nao devem ser levados
> a serios?? Fisicos nao resolvem problemas de matematica?? : )

Em muitos casos sim. Mas *estes* preprints em particular são escritos
de maneira muito imprecisa demais.

A pedido do Gugu segue abaixo o artigo do NYTimes.

[]s, N.

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The New York Times

April 15, 2003

Celebrated Math Problem Solved, Russian Reports

By SARA ROBINSON


A Russian mathematician is reporting that he has proved the Poincaré
Conjecture, one of the most famous unsolved problems in mathematics.
The mathematician, Dr. Grigori Perelman of the Steklov Institute of
Mathematics of the Russian Academy of Sciences in St. Petersburg, is
describing his work in a series of papers, not yet completed.
It will be months before the proof can be thoroughly checked. But if true,
it will verify a statement about three-dimensional objects that has haunted
mathematicians for nearly a century, and its consequences will reverberate
through geometry and physics.
If his proof is accepted for publication in a refereed research journal and
survives two years of scrutiny, Dr. Perelman could be eligible for a $1
million prize sponsored by the Clay Mathematics Institute in Cambridge,
Mass., for solving what the institute identifies as one of the seven most
important unsolved mathematics problems of the millennium.
Rumors about Dr. Perelman's work have been circulating since November, when
he posted the first of his papers reporting the result on an Internet
preprint server.
Last week at the Massachusetts Institute of Technology, he gave his first
formal lectures on his work to a packed auditorium. Dr. Perelman will give
another lecture series at the State University of New York at Stony Brook
starting on Monday.
Dr. Perelman declined to be interviewed, saying publicity would be
premature.
For two months, Dr. Tomasz S. Mrowka, a mathematician at M.I.T., has been
attending a seminar on Dr. Perelman's work, which relies on ideas pioneered
by another mathematician, Richard Hamilton. So far, Dr. Mrowka said, every
time someone brings up an issue or objection, Dr. Perelman has a clear and
succinct response.
"It's not certain, but we're taking it very seriously," Dr. Mrowka said.
"He's obviously thought about this stuff very hard for a long time, and it
will be very hard to find any mistakes."
Formulated by the French mathematician Henri Poincaré in 1904, the Poincaré
Conjecture is a central question in topology, the study of the geometrical
properties of objects that do not change when the object is stretched,
twisted or shrunk.
The hollow shell of the surface of the earth is what topologists would call
a two-dimensional sphere. It has the property that every lasso of string
encircling it can be pulled tight to one spot.
On the surface of a doughnut, by contrast, a lasso passing through the hole
in the center cannot be shrunk to a point without cutting through the
surface.
Since the 19th century, mathematicians have known that the sphere is the
only bounded two-dimensional space with this property, but what about higher
dimensions?
The Poincaré Conjecture makes a corresponding statement about the
three-dimensional sphere, a concept that is a stretch for the
nonmathematician to visualize. It says, essentially, that the
three-dimensional sphere is the only bounded three-dimensional space with no
holes.
"The hard part is how to tell globally what a space looks like when you can
only see a little piece of it at a time," said Dr. Benson Farb, a professor
of mathematics at the University of Chicago. "It was pretty reasonable to
think the earth was flat."
That conjecture is notorious for the many "solutions" that later proved
false. Indeed, Poincaré himself demonstrated that his earliest version of
his conjecture was wrong. Since then, dozens of mathematicians have asserted
that they had proofs until experts found fatal flaws.
Although many experts say they are excited and hopeful about Dr. Perelman's
effort, they also urge caution, noting that not all of the proof has been
written down and that even the most reliable researchers make mistakes.
That was the case in 1993 with Dr. Andrew J. Wiles, the Princeton professor
whose celebrated proof for Fermat's Last Theorem turned out to have a
serious gap that was repaired after months of effort by Dr. Wiles and a
former student, Dr. Richard Taylor.
Dr. Perelman's results go well beyond a solution to the problem at hand, as
did those of Dr. Wiles. Dr. Perelman's results say he has proved a much
broader conjecture about the geometry of three-dimensional spaces made in
the 1970's. The Poincaré Conjecture is but a small part of that.
Dr. Perelman's personal story has parallels to that of Dr. Wiles, who,
without confiding in his colleagues, worked alone in his attic on Fermat's
Last Theorem. Though his early work has earned him a reputation as a
brilliant mathematician, Dr. Perelman spent the last eight years sequestered
in Russia, not publishing.
In his paper posted in November, Dr. Perelman, now in his late 30's, thanks
the Courant Institute at New York University, SUNY Stony Brook and the
University of California at Berkeley, because his savings from visiting
positions at those institutions helped support him in Russia.
His papers say that he has proved what is known as the Geometrization
Conjecture, a complete characterization of the geometry of three-dimensional
spaces.
Since the 19th century, mathematicians have known that a type of
two-dimensional space called a manifold can be given a rigid geometric
structure that looks the same everywhere. Mathematicians could list all the
possible shapes for two-dimensional manifolds and explain how a creature
living on the surface of one can tell what kind of space he is on.
In the 1950's, however, a Russian mathematician proved that the problem was
impossible to resolve in four dimensions and that even for three dimensions,
the question looked hopelessly complex.
In the early 1970's, Dr. William P. Thurston, a professor at the University
of California at Davis, conjectured that three-dimensional manifolds are
composed of many homogeneous pieces that can be put together only in
prescribed ways and proved that in many cases his conjecture was correct.
Dr. Thurston won a Fields Medal, the highest honor in mathematics, for his
work.
Dr. Perelman's work, if correct, would provide the final piece of a complete
description of the structure of three-dimensional manifolds and, almost as
an afterthought, would resolve Poincaré's famous question. Dr. Perelman's
approach uses a technique known as the Ricci flow, devised by Dr. Hamilton,
who is now at Columbia University.
The Ricci flow is an averaging process used to smooth out the bumps of a
manifold and make it look more uniform. Dr. Hamilton uses the Ricci flow to
prove the Geometrization Conjecture in some cases and outlined a general
program of how it could be used to prove the Geometrization Conjecture in
all cases. He ran into problems, however, coping with certain types of large
lumps that tended to grow uncontrollably under the averaging process.
"What Perelman has done is to figure out some new and interesting ways to
tame these singularities," Dr. Mrowka said. "His work relies heavily on
Hamilton's work but makes amazing new contributions to that program."
If Dr. Perelman succeeds in resolving Poincaré, he will probably share the
Clay Mathematics Institute Award with Dr. Hamilton, mathematicians said.
Even if Dr. Perelman's work does not prove the Geometrization Conjecture,
mathematicians said, it is clear that his work will make a substantial
contribution to mathematics.
"This is one of those happy circumstances where it's going to be fun no
matter what," Dr. Mrowka said. "Either he's done it or he's made some really
significant progress, and we're going to learn from it."




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