Science Strings 2001 Conference: A Report The Annual International Conference on String Theory, STRINGS 2001 was held at Tata Institute of Fundamental Research(TIFR), Mumbai from January 5-10.The conference is part of an annual series, the previous ones being held at Los Angeles, Amsterdam, Santa Barbara, Potsdam and Michigan. The conference was jointly sponsored and organized by Clay Mathematical Institute(CMI), Cambridge USA, Abdul Salam International Center for Theoretical Physics (ASICTP), Trieste, Tata Institute of Fundamental Research, Mumbai, Harish Chandra Research Institute (HRI) Allahabad, IITs at Chennai, Kanpur and Mumbai, Institute of Physics Bhubaneswar, Institute of Mathematical Sciences Chennai, Saha Institute of Nuclear Physics (SINP),Kolkata and Utkal University, Bhubaneswar. The conference hosted 45 invited speakers and over 300 participants with 6 Indian speakers.The prominent invited speakers of this year's conference were Michael Green (Cambridge), David Gross (ITP Santa Barbara), Stephen Hawking (Cambridge), John Schwarz (Caltech), Ashoke Sen (HRI Allahabad) and Edward Witten (IAS Princeton). The five plenary sessions were addressed by Ashoke Sen (HRI Allahabad), Ignatius Antoniadis (CERN, Geneva), David Gross, Edward Witten (IAS Princeton) and Jeffrey Harvey (EFI Chicago). The conference was summarized by John Schwarz (Caltech Pasadena). The conference also hosted a Special Lecture Programme at TIFR on January 10 for non-specialists and the public. These were delivered by David Gross, Stephen Hawking and Edward Witten. There were six participants from IIT Kanpur: Sudipta Mukherji and the author were members of the National Organizing Committee, while the participants included one graduate and three undergraduate students. The conference reported the developments over the last one year in String Theory which is an ambitious attempt to unify in a single framework all the four fundamental forces of nature, namely Gravitation, Electromagnetism, Weak and the Strong Nuclear Forces. In contrast to the usual theories which treat elementary particles as point-like, this theory interprets particles as quantum excitations of a fundamental one dimensional string typically of 10 -33cm length. This is also expected to elucidate the outstanding issue of a quantum theory of gravity which will describe space-time at ultrashort length scales. Historically, string theory began as a failed attempt to explain the profusion of particles participating in the strong interactions. After a long dormant period, these theories were reinterpreted as fundamental theories involving all the four interactions. They seemed to provide a finite theory of quantum gravity which is characterized by low energy descriptions resembling standard theories in vogue. However they were only consistent with ten (9 + 1) space-time dimensions and are notorious for profusion of equivalent (non-unique) low energy descriptions.The extra six dimensions apart from the usual 3 + 1 were perceived to curl up into a small compact space of negligible radius at low energies. However, the problem of non-uniqueness of low energy limits perplexed theorists till the early 1980. The pioneering work of Ashoke Sen, Nathan Seiberg, Ashoke Sen and Edward Witten led to the realization that the seemingly inequivalent descriptions were in fact equivalent under the action of a novel symmetry which was termed duality. This was the beginning of the first insights into the non-perturbative structures and led to a complete change of perceptions in the theory. Later work by Joseph Polchinski (ITP Santa Barbara) illustrated that the fundamental degrees of freedom are not strings but higher dimensional wall like ( hypersurfaces) defects in space-time called D irichlet branes or D-branes. They could carry a particle quantum field theory and strings could be viewed as D-branes wrapped on shrinking (degenerate) hypersurfaces in the compact part of the space-time. Applications of these ideas indicated the presence of fundamental theories in 10 + 1 and 10 + 2 dimensions called M-theory and F-theory respectively. Some of the outstanding issues like entropy and strong coupling limits of these theories were discussed in this conference by Christopher Hull (Queen Mary College London) and Jorge Russo (Buenos Aires). While Michael Douglas (MIT), Suresh Govindarajan (IIT Chennai) Kentaro Hori (Harvard) and Joydeep Majumdar (HRI Allahabad) reported the various developments in the outstanding issue of the construction of curved D-branes. One of the striking consequences of D-brane physics was an understanding of black holes and their microscopic structures. Following this, Juan Maldacena (Princeton) conjectured the exciting equivalence of string theory in bounded spaces with constant curvature and negative cosmological constant and a particle theory on the boundary of this space in some limit, thus providing the first example of a connection between usual particle theories and a string theory. Recent developments in this area were reported in the conference by Mirjam Cvetic (U Penn.) , Steve Gubser (Princeton), David Gross (Santa Barbara), Michael Green (Cambridge), K S Narain (AS ICTP Trieste), Amit Giveon (Racah Inst. Jerusalem), Amanda Peet (Toronto), Nick Dorey (Swansea Wales), Igor Klebanov (Princeton), Volker Schomerus (AEI Golm) and Costas Bachas (Ecole Normale Paris). Stephen Hawking (Cambridge) reported coonections of this Maldacena conjecture with cosmology. An alternative approach to studying D-brane systems involving String Field Theory was reported by Ashoke Sen (HRI Allahabad), Barton Zweibach and Wsahington Taylor (MIT), Per Krauss (Chicago) and Samson Satashvilli (Yale). However many of the properties of these D-branes are yet to be explored. One recent major direction of research in this area involves particle theories and string theories in Non-Commutative spaces. These were reported by Rajesh Gopakumar and Shiraz Minwalla (Harvard), Soo Jong Rey (Seoul), and Jeffrey Harvey (Chicago) who spoke about a certain class of collective excitations (solitons) in these theories. N. Suryanarayana, Sumit Das (TIFR) and Hirosi Ooguri (Caltech) spoke about interaction couplings in these theories. Yoshi Kitazawa (Tokyo) and Gautam Mandal (TIFR) spoke about the relation of these non-commutative theories with Matrix Models which is an attempt to understand the fundamental aspects of the eleven dimensional M-theory. On another front recently, a low energy scenario for the universe was advocated. This involved restriction of matter and the visible universe on a smooth four dimensional wall (hypersurface) embedded in a higher dimensional space-time with the gravitational force inhabiting all the dimensions. The wall may be composed of a combination of D-branes. This Brane World Scenario is a major area of current research internationaly and of the High Energy Physics group at IIT Kanpur apart from activities in other areas. Several new investigations were reported about the relation of Brane Worlds with String Theories. Ignatius Antoniadis (CERN Geneva) and Luis Ibanez (Madrid) reported low energy string physics and embedding of brane worlds in string theory. Shamit Kachru (Stanford) and Eva Sliverstein (SLAC Stanford) spoke about the outstanding issue of supersymmetry breaking in these models. A unifying theme of the entire conference as summarized by John Schwarz was D-branes. It seemed that questions in the physics of D-branes will lead us further into the mysterious structures of nature at ultrashort length scales and may radically modify our current notions of space-time. Apart from this, there were a few lectures which are efforts to chart out new directions. One such direction is to explore the role of a de-Sitter geometry in string theory. Edward Witten, Jorge Russo, Petr Horava reported advances in the study and occurrence of de-Sitter geometries in string theory. The next annual conference Strings 2002 will be held in Cambridge UK and progress in further understanding of these theories are expected to be reported there.
Gautam Sengupta Department of Physics |
