Discussion:
braneworld
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giuseppe
2005-05-12 07:41:15 UTC
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could anybody tell me something about braneworld?
are there any good books or references you could give me?
Thanks
Urs Schreiber
2005-05-12 08:23:55 UTC
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Post by giuseppe
could anybody tell me something about braneworld?
are there any good books or references you could give me?
There are at least two different research areas associated with the term
"brane world" which share some common ingredients but are rather disjoint,
as far as I am aware.

One of them is concerned with making cosmological models where some (our)
universe is modeled as the worldvolume of a p-brane (3-brane in particular)
which itself propagates in a higher-dimensional spacetime.

Reviews of this approach are for instance

Roy Maartens:
Brane-world gravity
http://arxiv.org/abs/gr-qc/0312059


E. Papantonopoulos:
Brane Cosmology
http://arxiv.org/abs/hep-th/0202044

and

David Langlois:
Brane cosmology: an introduction
http://arxiv.org/abs/hep-th/0209261

These brane world models are often (not always) more "string inspired" than
really string theoretic in that all they (often) really take as input from
string theory is the idea that there may be something like branes in the
first place.


I am not an expert on this stuff, but personally I find it interesting that
in these brane models it is rather natural to find realizations of the
inflaton field in terms of tachyonic string modes between brane/anti-brane
pairs or in terms of "radions" or other moduli. See for instance

Burgess, C. P.; Martineau, P.; Quevedo, F.; Rajesh, G.; Zhang, R. -J.:
Brane-Antibrane Inflation in Orbifold and Orientifold Models
http://arxiv.org/abs/hep-th/0111025


The inflaton and the Higgs field are the two famous tachyonic fields that
are postulated by our currently best ("standard") models of cosmology and
particle physics, without having been observed yet.




The other research area often associated with the word "brane world" is that
part of string phenomenology which tries to realize the standard model of
particel physics by studying compactifications of string theory with
intersecting D-branes in the compact dimensions. Since there are open
strings stretching between D-branes and since the low-energy effective field
theory of generated by these depends on the nature of these D-branes, one
can engineer a wide variety of standard-model-like effective field theories
by considering string backgrounds with suitable configurations of
intersecting D-branes.

Reviews for this topic are for instance

Ralph Blumenhagen, Mirjam Cvetic, Paul Langacker, Gary Shiu
Toward Realistic Intersecting D-Brane Models
http://arxiv.org/abs/hep-th/0502005

or

Fernando Marchesano:
Intersecting D-brane Models
http://arxiv.org/abs/hep-th/0307252 .


Here, too, it is interesting how the important tachyon, in this case the
Higgs, is realized in these models. See for instance

D. Cremades, L.E. Ibanez, F. Marchesano
Intersecting Brane Models of Particle Physics and the Higgs Mechanism
http://arxiv.org/abs/hep-th/0203160


Lubos has a while ago reviewed a recent paper on this topic

http://groups.google.de/group/sci.physics.strings/msg/45ffb6f2b0b3f8a6?hl=de
Lubos Motl
2005-05-18 12:17:32 UTC
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Post by giuseppe
could anybody tell me something about braneworld?
are there any good books or references you could give me?
Definitely. There is one excellent book focusing squarely on the
braneworlds. It's Lisa Randall's "Warped Passages" and its British version
will appear on June 1st:

http://www.amazon.co.uk/exec/obidos/ASIN/0713996994/

Lisa Randall is almost definitely a/the world's leader in the branewolds.
The U.S. edition will appear in September.

http://www.amazon.com/exec/obidos/tg/detail/-/0060531088

"Braneworld" is a phrase that describes the models of the real world in
which the usual matter particles and non-gravitational forces are confined
to higher-dimensional generalizations of membranes - these generalizations
are called "branes" - objects that are embedded in a spacetime whose
dimension is even larger - much like a sheet of paper flies in
three-dimensional space. Only gravity "feels" the whole five-dimensional
(or higher-dimensional) spacetime while the other forces only know about
the membrane (brane) only. Surely, if these models are correct, our world
itself is a braneworld, too. ;-)
e***@yahoo.com
2005-05-28 11:08:13 UTC
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Post by Lubos Motl
Post by giuseppe
could anybody tell me something about braneworld?
are there any good books or references you could give me?
"Braneworld" is a phrase that describes the models of the real world in
which the usual matter particles and non-gravitational forces are confined
to higher-dimensional generalizations of membranes - these generalizations
are called "branes" - objects that are embedded in a spacetime whose
dimension is even larger - much like a sheet of paper flies in
three-dimensional space. Only gravity "feels" the whole five-dimensional
(or higher-dimensional) spacetime while the other forces only know about
the membrane (brane) only. Surely, if these models are correct, our world
itself is a braneworld, too. ;-)
Lubos,
Thanks to Peter Woit, I am aware that string theory may have problems
with the kaluza-klein approach due to the "landscape" problem -- that
there are more than 10^500 ways to compactifiy the additional 6-7
dimensions beyond the 4 large dimensions as Yau-Calubi manifolds. the
anthropic princple has been invoked suggesting at least one of these is
consistent with our world (the other worlds may exist as part of a
multiverse)

1 -What i wonder is whether the braneworld scenario has fewer landscape
problems, as they do not have to be "compactified" and hence more
"predictive" than the kaluza-klein approach.

2 Also, i am aware the braneworld approach may help explain why gravity
is so weak relative to the other forces (gravitons "leak" to higher
dimensions), but do the kaluza-klein compactification offer a similiar
explanation for the weakness of gravity?

3- is it possible for both to be partially correct, by breaking them
down, perhaps there are 4 large dimesions, 3 large "braneworld" 3
kaluza-klein compactified dimensions?
R.X.
2005-05-28 16:31:43 UTC
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Generically brane world models are dual, ie equivalent to other string
compactifications (sometimes even without branes), and thus won't have
any particular advantage or disadvantage as compared to other
descriptions of the same thing.

What you attribute to Woit is nothing new, and has been known since
decades to people working in the field.

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