jamesj
Site Admin
Joined: Mar 17, 2009
Posts: 3

Posted:
Sat Jan 22, 2005 12:24 am 

Before string theory won the full attention of the theoretical physics community, the most popular unified theory was an eleven dimensional theory of supergravity, which is supersymmetry combined with gravity. The elevendimensional spacetime was to be compactified on a small 7dimensional sphere, for example, leaving four spacetime dimensions visible to observers at large distances.
This theory didn't work as a unified theory of particle physics, because it doesn't have a sensible quantum limit as a point particle theory. But this eleven dimensional theory would not die. It eventually came back to life in the strong coupling limit of superstring theory in ten dimensions.
How could a superstring theory with ten spacetime dimensions turn into a supergravity theory with eleven spacetime dimensions? We've already learned that duality relations between superstring theories relate very different theories, equate large distance with small distance, and exchange strong coupling with weak coupling. So there must be some duality relation that can explain how a superstring theory that requires ten spacetime dimensions for quantum consistency can really be a theory in eleven spacetime dimensions after all.
Since we know that all string theories are related, and we suspect that they are but different limits of some more fundamental theory, then perhaps that more fundamental theory exists in eleven spacetime dimensions? These question bring us to the topic of M theory.
The theory currently known as M
Technically speaking, M theory is is the unknown elevendimensional theory whose low energy limit is the supergravity theory in eleven dimensions discussed above. However, many people have taken to also using M theory to label the unknown theory believed to be the fundamental theory from which the known superstring theories emerge as special limits.
We still don't know the fundamental M theory, but a lot has been learned about the elevendimensional M theory and how it relates to superstrings in ten spacetime dimensions.
In M theory, there are also extended objects, but they are called M branes rather than D branes. One class of the M branes in this theory has two space dimensions, and this is called an M2 brane.
Now consider M theory with the tenth space dimension compactified into a circle of radius R. If one of the two space dimensions that make up the M2 brane is wound around that circle, then we can equate the resulting object with the fundamental string (onebrane) of type IIA superstring theory. The type IIA theory appears to be a ten dimensional theory in the normal perturbative limit, but reveals an extra space dimension, and an equivalence to M theory, in the limit of very strong coupling.
We still don't know what the fundamental theory behind string theory is, but judging from all of these relationships, it must be a very interesting and rich theory, one where distance scales, coupling strengths and even the number of dimensions in spacetime are not fixed concepts but fluid entities that shift with our point of view.
From URL:
http://superstringtheory.com/basics/basic7.html 
Last edited by jamesj on Sun Dec 02, 2007 5:11 am; edited 1 time in total 

jamesj
Site Admin
Joined: Mar 17, 2009
Posts: 3

Posted:
Sat Jan 22, 2005 12:30 am 

¿ Can You See IT ???????
There are four Families (rather than 3 families), 22 constants (rather than 20), & 8 views of the 8 basic energies not 5 views of the 11 basic energies; etc., etc…
see Slide # 18 on URL:
http://7777777s.com/ppframe_files/frame.htm
Comparison of the Typical Viewpoint and the Viewpoint Where Absolutely Nothing Exists
The Basic Paradox’s existence & interactions create
the 4 forces and 8 Energies.
The 4 Forces, (realms of existence), each consist of a paradoxical duality.
These forces combine with the duality to produce the 8 factors of life.
These 4 forces & 8 factors create 8 fundamental vibrations, (8 Energies);
7 are easily perceived & 1 is not.
The 8 factors combine with the 8 Energies to produce
16,777,216 dimensions (8 to the eighth power),
(these dimensions exist simultaneously in the same space & time).
We usually perceive a maximum of 4,096 of them; but,
because of our human perspective
we think there are approximately 3,000, (i.e. ichinen sanzen).


