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A clutch of five papers this period confirms the tight grip string theory has on the Physics Top Ten. The stitch-up is composed of Hot Papers #2, 5, 6, and 10, all linked by a beautiful web of complex theory at the very frontiers of reductionist physics, while #9 stands back and looks at model building. The tension here is about weaving new models of reality using tools of mathematics and physics that are theorems and constructs in hyperspace. The level of citations and consistency with which the invisible college of string theorists cite each other suggest that something momentous is under way in fundamental physics. String theory is a framework for a unified description of all interactions, including gravitation, in a way that is consistent with quantum theory. The basic idea is to take the notion of a point particle that is described by its worldline in spacetime and replace it with a string which is either a line segment or a circle that describes a worldsheet in spacetime. String theory takes place in Minkowski space with 10 or more dimensions.
Edward Witten, of the Institute for Advanced Study, Princeton, is the dean of string theory, and his default setting is to have at least one paper in the Physics Top Ten at all times. (As the lead story in this issue indicates, Witten ranks among the most-cited physical scientists of the decade; see table on page 2.) For Science Watch, Witten gives the following roundup of recent papers. "By mid-1995 it had become clear that a new kind of miniature black hole called a Ramond-Ramond (RR) charge was important in the general understanding of string theory. In paper #2 Joe Polchinski [University of California, Santa Barbara] presents a new understanding of these objects according to which their basic property is that they are points in space on which strings can end." By August 1997, #2 had logged 167 citations. That is quite high for a purely theoretical paper currently battling Bose-Einstein condensation (#3, #4) and laser diodes (#1). The string community is enormously impressed with #2 because it solves two problems at once: the inclusion of RR states in string theory and the interpretation of RR charged solitons arising in the context of string duality. Speaking of his own #6, Witten explains, "I use the new understanding from Polchinski to analyze the formation of bound states of different kinds of string. This was an important question in type IIB superstring theory, and in answering it I introduced gauge theory techniques that had many later applications. They are, for example used in Hot Paper #5 by Andy Strominger [UC Santa Barbara] and Cumrun Vafa [Harvard University], which is the first paper in which the quantum states of a black hole are counted from first principles in a controlled way." As a result of this paper there has been much activity on the role of black holes in string theory as well as renewed vigor in the attempt to understand string theory as a theory of quantum gravity.
Vafa takes the debate to higher dimensions in a new entry at #10, which attempts to find a natural interpretation for strings in the context of a hypothetical 12-dimensional construct called F-theory. "This paper is hotly cited because it leads to many new constructions of string vacua in 8 and lower dimensions, and it has shed light on many new interesting physical phenomena," Vafa tells Science Watch. New entrant #9 on low-energy super-symmetry is also strictly fundamental
but not so reductionist. This iconoclastic report looks at broken symmetry at low energies
and sets out new models which are highly predicative. Up to 100 assumed parameters are
brushed aside and replaced by a handful of new ones, but at a cost of complexity.
Cosmology is addressed too, as dark-matter enthusiasts and inflationary aficionados are
challenged in the battlefield of the very early universe. This paper concludes with the
dark warning of numerous challenges of string-based theories for cosmology, but on an
upbeat note it points out that current experimental technologies can establish whether or
not its conclusions are true. |
Dr Simon Mitton
directs science and professional publishing
for Cambridge University Press, Cambridge, UK
| Science
Watch®, November/December 1997, Vol. 8, No. 6 Citing URL: http://www.sciencewatch.com/nov-dec97/sw_nov-dec97_page7.htm |
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Strings
Maintain Tight Wrap on Physics Top Ten
.
