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Re: Photons in other dimensions



I must have missed Hugh's posting or I'd have commented.
It's not a question of how many dimensions are "enough". Different string
theories may have different critical dimensionalities. Purely bosonic
string theories only "make sense" in 26 dimensions. (26 dimensions was
discovered in the office next to mine in the early '70's by Sakita).
Others work in 10 dimensions. The "extra" dimensions are "rolled up"
in tiny "tubes" that may be unobservable. The Randall-Sundrum dimension,
on the other hand, are "large", but only "permit" gravity.

I consider the importance of Randall-Sundrum to be the fact that it
provides a counter-example to some of the arguments that are used to claim
that supersymmetry "must" exist.

Randall-Sundrum also predicts a whort-distance modification of Newton's
law of gravity. Experiments are currently in progress at U. of
Washington.
Regards,
Jack






IOn Fri, 16 Apr 2004, Larry Smith wrote:

At 9:37 PM -0400 4/15/04, Hugh Logan wrote:

The Kaluza-Klein theory was largely forgotten until the fairly recent
advent of string theory, of which it was a predecessor. Earlier versions
of string theory had something like 26 dimensions, but it was shown that
10 dimensions could do just as well.

My understanding (very limited) is that we need one more (total of 11) in
order to make the 5 versions of string theory unify into one M-theory.

According to fairly recent developments in string theory, there are
subspaces within the nine spatial dimensions of string theory caled
branes, which can have dimensios 1, 2, ... up to 9. A one dimensional
brane would be a point, a 2-d brane would be a membrane,

Wouldn't one dimensional be a line or string?

Larry


--
"Trust me. I have a lot of experience at this."
General Custer's unremembered message to his men,
just before leading them into the Little Big Horn Valley