Subject: Re: What is superstring?

From: [email-masked] (Grimover)
Date: 18 Mar 1996 08:54:31 -0500

Warren

>Does anybody know what the superstring theory proposes?
The *heterotic* superstring theory proposes that instead of being "points"
in space, all particles in physics are really tiny loops 10^33 cm (the

[Mod. note: that's 10^(-33), of course. -TB]

Planck Length)  in diameter; they only appear to be points due to their
small size.  This length would be the lowest vibratory mode of  these
"closed loop" strings.  Excitations of the string cause higher modes of
vibration which would express different forms of matter.  String theory
only requires three fundamental physical constants, c, hbar and G.  All
other properties of matter and its interactions arise from the geometry of
the superstring.

What is extraordinary about this theory is that it creates a rich
mathematical framework which has been demonstrated to be mathematically
consistent with the Standard Model (which governs the Electromagnetic and
Weak forces), the "Superstandard Model" (which attempts to unify the
Strong, Electromagnetic and Weak forces) *and* General Relativity!  To my
knowledge this is the only theory currently in existence which can make
this claim!  For this reason, string theory has been claimed to be the
first ever candidate for a "Theory of Everything," i.e., a single
framework for the analysis of *all* physical phenomenon.

There are, of course, some major problem with this theory, first and
foremost that there are several heterotic string theories (for instance,
4, 6, 8 and 10 dimensional) with thousands of solutions, only a few of
which provide predictions in the "low mass sector" (that is, those that
could be verified at energies which can be created in current or future
particles accelerators or in the analysis of Cosmic Rays).  However, as
Steven Weinberg points out, even if none of these early predictions pan
out, the theory shouldn't be rejected if at first glance it doesn't make
predictions we can verify, because it provides many insights on its own,
making it what Weinberg calls a "beautiful theory."  

Another major problem is that this theory can't currently make make
precise calculations of the sort possible with the Standard Model, because
its mathematical framework has not yet been fully fleshed out.  However,
as Edward Witten has pointed out, Quantum Electrodynamic took about 50
years from the time of Planck (1900) to the time of Feynman and Schwinger
to reach its very high precisions, and it may take at least that long for
the theory of superstrings.  Witten has said that Superstring theory is "a
21st century theory which was accidentally discovered by 20th century
theorists."  In other words, previously in the history of physics,
mathematicians have been lead by their sense of mathematical beauty to
create formal structures that later on physicists have found to be useful,
even if the mathematicians had no such use in mind.  An example of this
would be Lie Groups, created by Norwegian mathematicial Sophus Lie in the
19th century, which turned out to be the key to the Standard Model.  With
superstrings, however, theorists and mathematicians are working together
to develop the formal structures necessary to fully describe superstrings.

There are other problems with the theory, but not which would even come
close to causing its rejection, since it is naturally free of anomalies
and infinites of previous attempts at a quantum theory of gravity such as
SuperGravity.  According to Michio Kaku, over 1000 papers on Superstrings
were published in 1995, so I think its safe to say it is currently a major
area of research.

Ed Bishop
======================================================
"A true Scientist must question everything, even their own questions!"
-- Dr. Charles R. Pellegrino