Article for Novices: Brane New World
sol
multidimensional space. Could this 'brane-world' concept unify gravity
with nature's other fundamental forces?" by Ronald Pease
http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v411/n6841/full/411986a0_r.html
sol
> "Some theorists propose that our Universe exists as a slice through...
I thought I would add this. Lisa Randalls thinking, could be very
close to the ideas expressd here in terms of brane scenarios and
planck brane?
------------------
The 5D Space-Time Consortium
"We are a group of physicists and astronomers working on a
five-dimensional version of general relativity. Our work differs from
Kaluza-Klein theory (the basis of superstrings) in that we do not
assume compactification of the extra dimension. This means that new
terms (those involving the 5th coordinate) enter into physics, even at
low energies. In 4D spacetime these can be interpreted as matter and
energy. We move them to the right-hand side of the 4D field equations
and take them to describe an induced energy-momentum tensor. In fact,
we have shown that no 5D energy-momentum tensor is required. 4D matter
of all kinds can arise as a manifestation of a higher-dimensional
vacuum. This is one way to realize Einstein's dream of transmuting the
"base wood" of matter into the "pure marble" of geometry -- that is,
of unifying the gravitational field, not just with other fields but
with its source."
http://astro.uwaterloo.ca/~wesson/intro.htm
I add it not to deter from String/M theory discussion but to gain more
more on the ideas of brane scenarios. These are "generalizations" from
a novice perspective.
sol
Brane - Interview with Dr. Michael Duff
"Hawking wrote down the formula for what that entropy should be. It's
a famous formula that says the entropy is one-quarter the area of the
event horizon of the black hole. He used a kind of macroscopic
thermodynamic argument to reach this conclusion, but if what he was
saying is correct, there should also be some microscopic explanation.
In the subsequent 20 years, nobody could figure out what this
microscopic origin of black hole entropy actually was. Using these new
ideas of branes and M theory, that problem has now been solved.
Another thing it does, and this may be too early to tell whether it's
good or not, is M theory now offers dozens of ways of trying to do a
real-world analysis to see how the standard model of particle theory
fits into the scheme of things. Depending on how you look at it, that
can be good or bad. Now we're left with a different kind of uniqueness
problem. How does nature single out the one way of doing things? It
also means we have some new avenues of exploration that we didn't
think were open to us before. And then there's this large-dimension
industry, which is a spin-off from M theory, as well."
sol
http://www.isepp.org/Media/Hawking%20Images/HawkingA26w.jpg
Stephen Hawking actually attributes this to someone else. Does anyone
know who that might be for historical accuracy?
[Moderator's note: Indeed, Stephen Hawking has virtually nothing to do
with the discovery of the braneworlds, except that he might be giving
lectures about it and his team might be creating pictures with the branes
and with Hawking, and those pictures may influence the laymen who know
virtually nothing about physics (and nothing about its history and its
people). Crediting the correct people for at least the basic discoveries
is necessary not "just" for historical accuracy, but it might be necessary
for accepting another post of this type. There is no space for a complete
history here, but the braneworlds are connected with the paper of Nima
Arkani-Hamed, Savas Dimopoulos, and Gia Dvali who in 1998 proposed the
"flat" braneworld, building on insights of Joe Lykken; Joe Polchinski;
and Petr Horava and Edward Witten, among others. The warped braneworlds
were proposed by Lisa Randall and Raman Sundrum in 1999, and many people
have studied them since. LM]
"Brane: An object, which appears to be a fundamental ingredient of
M-theory, that can have a variety of spatial dimensions. In general, a
p-brane has a length in p directions, a 1-brane is a string, a 2-brane
is a surface or membrane
Brane World: A four-dimensional surface or brane in a higher
dimensional spacetime"
sol
> Origin of "Brane New World"?
>
> http://www.isepp.org/Media/Hawking%20Images/HawkingA26w.jpg
>
> Stephen Hawking actually attributes this to someone else. Does anyone
> know who that might be for historical accuracy?
>
> [Moderator's note: Indeed, Stephen Hawking has virtually nothing to do
> with the discovery of the braneworlds, except that he might be giving
> lectures about it and his team might be creating pictures with the branes
> and with Hawking, and those pictures may influence the laymen who know
> virtually nothing about physics (and nothing about its history and its
> people). Crediting the correct people for at least the basic discoveries
> is necessary not "just" for historical accuracy, but it might be necessary
> for accepting another post of this type. There is no space for a complete
> history here, but the braneworlds are connected with the paper of Nima
> Arkani-Hamed, Savas Dimopoulos, and Gia Dvali who in 1998 proposed the
> "flat" braneworld, building on insights of Joe Lykken; Joe Polchinski;
> and Petr Horava and Edward Witten, among others. The warped braneworlds
> were proposed by Lisa Randall and Raman Sundrum in 1999, and many people
> have studied them since. LM]
I appreciate the moderators response here as it is now evident how
these articles can help with information, and the ideas of what lead
to branes.
I would like to continue with the people that have been mentioned, as
I have contained these in my resources and found them very important
in learning to understand the historical from a novice position.
http://www.sciencewatch.com/may-june2001/savas-dimopoulos-big.jpg
Savas Dimopoulos
For all its successes, the standard model is nevertheless
unsatisfying. There are 18 or so free parameters, such as the electron
mass, that seem arbitrary: they have to be determined experimentally.
What is the origin of the masses of the fermions? How can the strong
and electroweak interactions be unified? And what of the gravitational
force, on which the standard model is silent?
"In 1981 Savas Dimopoulos of Stanford University and Howard Georgi of
Harvard University proposed the supersymmetric extension to the
standard model. Revolutionary at the time, it is now accepted by many
physicists. Dimopoulos has been strongly driven in his research by a
desire to understand what lies beyond the standard model. His
contributions have included work on grand unified theories of
baryogenesis, which would provide an explanation of the origin of
matter. Jointly with Stanford colleague Nima Arkani-Hamed and Gia
Dvali of ICTP, Trieste, Italy, he has proposed an audacious solution
to the problem of explaining the weakness of the gravitational force.
The proposal invokes new large dimensions accessible to the graviton.
Among the extraordinary implications of this thinking is the notion
that our entire universe is a single point in space of extra
dimensions, and is but one of innumerable parallel universes. Thanks
to this work, Dimopoulos has recently been a mainstay of the Physics
Top Ten—one of the trio's papers on this subject has ranked among
physics's most cited for more than a year (see table on next page,
paper #3)."
http://www.sciencewatch.com/may-june2001/sw_may-june2001_page3.htm
_______________________________________________________________________________
Web page of SPS: http://schwinger.harvard.edu/~sps/
Posted via: http://groups.google.com/groups?group=sci.physics.strings
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
sol
http://www.physics.harvard.edu/nimaphoto.jpg
What got you started on the research in large extra dimensions, for
which you're so highly cited?
"Well, I had just obtained my degree from UC Berkeley and had just
started my post-doc at the Stanford Linear Accelerator Center (SLAC).
As a Ph.D. student, I had been working on what was a mature field. It
was supersymmetry at low energies: the point was that everyone expects
some sort of new physics to come in at a distance around 10-17
centimeters, and what we can see at accelerators today goes up to
10-16 centimeters. For 20 years, the dominant view has been that a new
symmetry of nature will be revealed, called supersymmetry, and it will
manifest itself in a variety of new particles with very distinctive
properties. But this framework has been around for 20 years, and it
may still very well be right, and it's what I spent my time exploring
as a graduate student, but by the time I got to my post-doc I was
definitely getting restless, wondering if there was some completely
different framework for what might be happening at the 10-17
centimeter scale.
When I arrived at SLAC, I immediately started talking to Savas
Dimopoulos, who's one of the people responsible for inventing this old
paradigm of supersymmetry. We quickly realized we were both on the
same page as far as wanting to think about something completely
different. Gia Dvali was also interested in thinking that way. So the
three of us started thinking about whether we could make sense of some
older ideas about extra dimensions that might be large compared with
what people normally thought about extra dimensions."
http://www.esi-topics.com/brane/interviews/DrNimaArkani-Hamed.html
sol
the generalizations, and hope some one might correct here for me?
Again, I understand the need for good visualizations of what is being
imparted here from branes scenarios, and that it is mathematically
driven.
http://new.math.uiuc.edu/optiverse/img/rs11-107.jpeg
Bubble eversions
An Introduction to Geometrodynamics
"The existence of gravitational waves is a prediction of the General
Theory of Relativity which is Einstein's explanation of the
gravitational interaction (1915). The basic idea is:
Gravity is no force but an aspect of the geometry of spacetime.
Space is not an absolute invariant entity, but is influenced by the
distribution of mass and energy in the Universe. The basic principle
is:
Matter tells space how to curve, and space tells matter how to move.
Large masses introduce a strong curvature in spacetime. Light and
matter are forced to move according to this metric. Since all the
matter is in motion, the geometry of space is constantly changing.
Hence Geometrodynamics is a better name for Einstein's theory of
gravitation. In order to derive the basic field equation, one has to
relate the curvature of space to the mass/energy density:"
G = k T
http://www.physics.gla.ac.uk/gwg/geodynamics.html
sol
It was important to understand the group here, and some of their
information, and Georgi Dvali being part, I wanted to see what he was
doing last?
http://online.itp.ucsb.edu/online/susy_c99/dvali/oh/02.html
[Moderator's note: if you did not understand the purpose of this post, you
might be happy to hear that the moderator did not understand it either
- but it wasn't quite a sufficient reason to reject the post, according
to the charter. LM]
sol
Petr Horava
"String theory represents a systematic modification of general theory
of relativity, so that it is compatible with quantum mechanics.
Therefore, we can address some of the long-standing puzzles of quantum
gravity in the string theoretical framework, such as the statistical
interpretation of the thermodynamic Bekenstein-Hawking entropy of
black holes. In a class of stringy black holes amenable to analysis,
the entropy has been explained as counting of stringy states. This
result further confirms that string theory is indeed on the right
track to describe the microscopic physics of quantum gravity, as the
correct degrees of freedom have already been identified."
http://www.physics.berkeley.edu/research/faculty/horava.html