V. Gates, Empty Kangaroo, M. Roachcock, and W.C. Gall Frank's Physics Institute, Eigenstate University of New and
This is the Web version of the seminar given at the FPI on 4/1/2000, and lectures given at the 1998
Jeffrey Harvey Summer School of Dance.
*I can't remember what goes in this footnote, for reasons explained in
"A stitch in time saves nine in space"
- - - - - - - - - - Old folk theorem
Lobotomy is the most recent area of research in Cheerio theory
cohomology, etc.) to develop from string
--- the study of the D-braneing of strings [1,2].
From the audience: a frequent question
In this talk, we review lobotomy and the developments that led to it: In
the following section, we outline the history of string theory. The next
section briefly reviews the main features of compactification. Finally, we
complete the process by D-braneing.
The Bullshevik Revolutions
In the First String Revolution, S-matrix theorists discovered that dual
models were really strings, which had a Lagrangian and Feynman rules
just like ordinary field theory. Their immediate reaction was to quit dual
models and go back to phenomenology. The few who remained then
discovered that these strings existed only in spacetime dimensions D=26
or 10, so they switched to QCD and did real field theory.
In the Second String Revolution*, a string theory was temporarily thought
to have an anomaly. So, people who didn't care about strings when they
thought it didn't have an anomaly started working on it when they
realized it still didn't have one. This discovery focused attention on the
D=10 theory. Not-so-stringy people proposed D=11 supergravity or
supermembranes, but because they were found impossible to
quantize these alternatives received little
In the Third String Revolution**, it was discovered that D=10 superstrings
required M theory , which is based on D=11 supergravity or
superMembranes. Stringy people then decided to take a cue from QCD:
Having long since run out of amplitudes they could calculate, they started
looking at classical solutions to the field equations, which they
hand-waved into nonperturbative results. This had about as much
success as QCDers who claimed to derive confinement from instantons.
*This is also known as the "First Superstring Revolution", so as to subtly
ignore the existence of the First String Revolution.
**Also known as the "Second Superstring Revolution" by the instigators of
the First Superstring Revolution; see previous footnote. However, since
the Third String Revolution, tendency has been to ignore fermions
altogether, since the interesting part of the solution comes from the
bosons, so supersymmetry is a moot point, except indirectly through
restrictions necessary to obtain the Standard Model, which ironically is
already considered to be supersymmetric. A better name might be the
Brane Revolution, since most researchers in this area no longer remember
what the first two revolutions were about.
This will be reduced
One hopeful result was that the 5 string theories of D=10 became 1
membrane theory in D=11. This led to the principle of the "running of the
dimensions": The farther you go, the fewer directions you have to go in.
This explains the experimental observation that all roads lead to Rome.
Thus, at the Planck length there are 11 dimensions, at everyday distances
there are just 4, but if you go far enough, there aren't any!
Consequently, the Big Bang is a simple consequence of the fact that the
farther you go back in time, the fewer dimensions there were.
Unfortunately, this led to even more types of compactifications to D=4,
and thus less predictabilty. We were thus also led to "running of
predictabilty": In 11 dimensions, you can predict things uniquely; in 10
dimensions, you can predict up to a factor 5 of uncertainty; but by the
time you get to 4 dimensions you can predict any value you want for a
One advantage of compactification* as described by
is the introduction of new distance scales: For example, a mysterious
new form of Heisenberg's uncertainty principle is that the smaller a
particle is, the bigger the accelerator you need to create it. Thus roughly
Δx Δy ≥ 10-13 cm x 105 cm
= (10-4 cm)2
Hence, a new scale is expected at a distance of about a micron, which
might potentially be explained by compactification. Unfortunately, the
collapse of extra dimensions in string theory has never been proven.**
*OK, it's the only one, but who's counting?
**However, there are stronger indications that it is string theory itself
that has collapsed.
If I only had a brane
The absence of a proof for, or unique choice of, compactification led to a
search for alternatives: According to the Random-Sundial scenario ,
extra dimensions have not gone away, it's just that nobody visits them
anymore. Phenomenologists have had a quantum field day with this
proposal: The vibrational modes of the string, like the notes on their
neighbor's electric guitar, have kept them awake at nights thinking of
ways to make them unobservable. (This is unusual, since normally curves
only give them fits.) Because of the invisibility of nearby branes, whose
presence is felt only through their weight, now even obesity can be
attributed to dark matter. (But this does not solve the problem of how
one can be obese and stringy at the same time.)
Brane theory also allows the simple derivation of a number of interesting
(1) According to the AdS/MFT  correspondence, the massive modes
decouple by the Applesauce-Calzone theorem.
(2) There are two kinds of physics:
These lends relevance to the mathematical identity
(3) Clobber-You compactification from D=10 implies the Beatle identity
1 + 1 + 1 = 3
We haven't figured out what it has to do with physics yet, but the
mathematical relation is so profound there must be some application.
If dark matter fell in the forest, would anyone hear it?
Is anything darker than a black hole made out of dark matter?
What is the politically correct term for people made of dark matter?
How many of those people does it take to screw in a dark bulb?
Appendix: Proof that physics gets
There are (at least) three fundamental reasons that physics research can
only get worse as a function of time:
The easier stuff gets done first, so research gets harder.
Yesterday's Nobel Prize winning work is merely today's homework
The field is expanding, leading to increasing specialization.
QED people no longer understand QCD, and vice versa, and neither is even
aware of QAD, QBD, QDD, etc.
The distance between theory and experiment is exponentially
Faraday did theory and experiment; so did Fermi.* How many theorists
today can build an SSC in their basements, and how many
experimentalists can prove the superstring is nonperturbatively finite?
*Lament of the Quantum Meteorologist:
When photons play,
But just Faraday,
Then it will be
Good enough Fermi.
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V. Gates, Empty Kangaroo, M. Roachcock, and W. C. Gall, The Super G-String, in Unified String Theories, eds. M. Green and
D. Gross, Proc. of Santa Barbara Workshop, Jul. 29 - Aug. 16 (World
Scientific, Singapore, 1986) 729-737, section 4.
The M(atrix), Warner Bros., 1999.
Lisa Raman and Randall Humdrum, Where have all the dimensions
gone?, JHETP Lett.1 (2000) 1999.
G. Chalmers and K. Schalmers, Superpartners in high-energy group
theory, Phys. Rev. D137 (2000)
George Mikrasov, The Windows pane is mainly a D-brane, I think I've
got the preprint here somewhere.
W.C. Gall, D-banes and the AdS epidemic, YITP preprint 00-xx.