Maldacena’s conjecture has led to a flood of research that has yet to show signs of ebbing, and string theorists find themselves still firmly ensconced in what they consider their latest string-theory revolution. Among the leaders of this revolution is Arkady A. Tseytlin of The Ohio State University. Tseytlin’s June 2002 article in Physical Review D, "Exactly solvable model of superstring in plane wave Ramond-Ramond background," co-authored with Ruslan R. Metsaev, has now been cited more than 200 times (see table below) and appeared in the Physics Top Ten in 2004, most recently at #7 in the previous issue (see Science Watch, 15[6]: 6, November/December 2004). Although that paper has now surpassed the two-year age limit for inclusion in the Hot Papers database, Tseytlin currently has seven other reports, all published within the last two years, in the latest bimonthly update of the Hot Papers file. Those papers, along with the Physical Review D report and a dozen other articles in the last decade with over 100 citations each, demonstrate that Tseytlin is among the most influential physicists in the world these days.

Tseytlin, 48, obtained his master’s degree in physics from Moscow University in 1980 and his Ph.D. in theoretical physics three years later from the Lebedev Physics Institute in Moscow. He went on to get his D.Sc. degree from the Russian Academy of Sciences in 1991. In the early 90s Tseytlin lived a peripatetic life, working as a visiting scholar at Kings College in London, Johns Hopkins University, Trinity College in Cambridge, and at CERN in Geneva. Since 1999, he’s been a full professor at Ohio State and, since 2000, a professor at Imperial College as well.

  How would you describe Maldacena’s conjecture in the simplest possible way, and how important do you think it is to the progress of string theory? In other words, how revolutionary is this latest string-theory revolution?

Tseytlin: Well, Maldacena’s conjecture simply says that in one limit of some fundamental string equations you have a description in terms of weakly interacting strings, and in the other limit you have a description in terms of weakly interacting local fields of gauge theory. And that’s really, on some level, as big as the particle-wave duality of quantum mechanics, where we may think of wave as being a collective excitation of many particles.

  What’s been the focus of your work over the past decade, and how has it changed with Maldacena’s conjecture?

Tseytlin: Over the last decade, we’ve been concentrating on the relationship between string theory, black holes, and new extended objects called D-branes, which are multidimensional lumps like membranes. The idea is to connect string theory to gauge theories or Yang-Mills theories of the kind used to describe high-energy behavior of elementary particles. This aspect came to light very strongly with Maldacena’s conjecture. In fact, Maldacena’s conjecture was about a precise relationship between a supersymmetric gauge theory and a string theory that lives in a certain curved space.

  How did you respond to his conjecture, and why has it had such extraordinary impact in the field?

Tseytlin: When Maldacena suggested that a string theory should be dual to a gauge theory, he did it without actually presenting all the details of that string theory. The contribution from me and Ruslan Metsaev, of Lebedev Institute in Moscow, was to construct a precise form of what’s called the "action" of that string theory, which essentially defines the theory. Together we wrote two papers that have been the most influential. The first and more fundamental one was published in 1998 (R.R. Metsaev, A.A. Tseytlin, Nucl. Phys. B, 533[1-3], 109-26, 1998). In a more recent work we’ve been looking at a specific limit of that earlier work, a limit that’s under more mathematical control, allowing one to make more progress.

  At the risk of sounding naïve, when you say you’re making more progress, what are you progressing toward in this kind of theoretical endeavor?

Tseytlin: The idea here is to understand in all possible detail this scenario: given a question on the gauge-theory side of this duality—for example, computing some scattering amplitude or some particular characteristics of this quantum field theory—how can we answer that same question using the string theory that is supposed to be equivalent to the gauge theory? We want to understand this duality between this Yang-Mills gauge theory and string theory. In the process of finding a solution to that problem, we hope to develop tools that will allow us to address string and gauge theories that describe the real world. The hope is that once we have a good understanding of the duality between gauge theory and string theory, we may be able to apply the same ideas to problems involving black holes, cosmology, the structure of the compact extra dimensions in our world, and possibly a whole lot of other problems. That’s our motivation. But at the moment we want to go step by step, so we look at relatively simple problems. Proving this Maldacena duality provides a stepping-stone on the way.

  And what does it mean to say that you came up with a "precise form" of Maldacena’s conjecture in your 1998 paper?

Tseytlin: The explicit formulation of the Maldacena conjecture was given shortly after his seminal work, by Steven Gubser, Igor Klebanov, Alexander Polyakov, and Edward Witten. What Metsaev and I did was to find the expression for the Maldacena string, which moves in a very particular 10-dimensional curved space. That step was "non-trivial," because it’s a complicated string theory. It wasn’t the kind of string theory that theorists were used to. And indeed, as our work demonstrated, it’s very hard to work with this theory; it’s not easy to solve it in the way this was done in flat space. String theory is essentially linear in flat space. So we can solve its equations of motions. We can quantize it. We can describe the elementary vibration modes of the strings. But doing the same for that Maldacena string is highly non-trivial.

  So how do you proceed in that situation?

High-Impact Papers by Arkady Tseytlin et al., Published Since 1996 (Ranked by total citations) Rank Paper Citations 1 R.R. Metsaev, A.A. Tseytlin, et al., "Exactly solvable model of superstring in plane wave Ramond-Ramond background," Phys. Rev. D, 65(12): 126004, 2002. 222 2 A.A. Tseytlin, "On non-abelian generalisation of the Born-Infeld action in string theory," Nucl. Phys. B, 501(1): 41-52, 1997. 211 3 A.A. Tseytlin, "Harmonic superpositions of M-branes," Nucl. Phys. B, 475(1-2): 149-63, 1996. 190 4 A.A. Tseytlin, "Self-duality of Born-Infeld action and dirichlet 3-brane of type IIB superstring theory," Nucl. Phys. B, 469(1-2): 51-67, 1996. 167 5 M. Cvetic, A.A. Tseytlin, "Solitonic strings and BPS saturated dyonic black holes," Phys. Rev. D, 53(10): 5619-33, 1996. 147 SOURCE: Thomson Scientific Web of Science

Tseytlin: Theorists started thinking that maybe they could take various limits of the Maldacena theory, which simplifies the structure. So that’s how we get closer to the recent work. It was inspired by a suggestion by Matthias Blau, Jose Figueroa-O’Farrill, Chris Hull, and George Papadopoulos in 2001 to look at a limit of this 10-dimensional curved space and see where it simplifies. They identified a particular limit, which is called plane-wave limit. And then Metsaev, in his own paper (R.R. Metsaev, Nucl. Phys. B, 625[1-2]: 70-96, 2002), which has even more citations than our joint paper, noted that in that particular limit of this geometry, our string theory of 1998 simplifies dramatically. It becomes quadratic, leading to linear equations, like Newton’s equations for a pendulum. So you can solve them explicitly. Subsequently, in my 2002 paper with Matsaev, we solved this string theory explicitly and analyzed it in all its details. At about the same time there appeared a remarkable paper by David Berenstein, Juan Maldacena, and Horatiu Nastase (D. Berenstein, et al., J. High Energy Physics, Art. No. 013, April 2002). It discussed what we now call the BMN limit, i.e., the analog of the plane-wave limit on the gauge-theory side of the Maldacena duality. And with all this, we were finally able to see this duality at work in a very explicit way. We could see how one quantity on the gauge-theory side is computable and equal to the corresponding quantity of the string-theory side. So Maldacena’s conjecture was verified in that limit. That was a big step forward because previously people weren’t able to see how Maldacena’s conjecture could be checked beyond a few simplest symmetry-based tests. The idea of taking this limit on both sides—on the string-theory side and the gauge-theory side—was very, very important.