14197742
String theory and gravity
It is pointed out that string-loop effects may generate matter couplings for the dilaton allowing this scalar partner of the tensorial graviton to stay massless while contributing to macroscopic gravity in a way naturally compatible with existing experimental data. Under a certain assumption of universality of the dilaton coupling functions, the cosmological evolution drives the dilaton towards values where it decouples from matter. At the present cosmological epoch, the coupling to matter of the dilaton should be very small, but non zero. This provides a new motivation for improving the experimental tests of Einstein's Equivalence Principle.
118103020
Metastable States of Two-Dimensional Isotropic Ferromagnets
15693064
Gauge Theory Correlators from Non-Critical String Theory
Abstract We suggest a means of obtaining certain Green's functions in 3+1-dimensional N =4 supersymmetric Yang-Mills theory with a large number of colors via non-critical string theory. The non-critical string theory is related to critical string theory in anti-deSitter background. We introduce a boundary of the anti-deSitter space analogous to a cut-off on the Liouville coordinate of the two-dimensional string theory. Correlation functions of operators in the gauge theory are related to the dependence of the supergravity action on the boundary conditions. From the quadratic terms in supergravity we read off the anomalous dimensions. For operators that couple to massless string states it has been established through absorption calculations that the anomalous dimensions vanish, and we rederive this result. The operators that couple to massive string states at level n acquire anomalous dimensions that grow as 2 ng YM 2N 1/2 for large `t Hooft coupling. This is a new prediction about the strong coupling behavior of large N SYM theory.
18650930
The Theory of turbulence in two-dimensions
Abstract The methods of conformal field theory are used to obtain series of exact solutions of the fundamental equations of the theory of turbulence. The basic conjecture, proved to be self-consistent, is the conformal invariance of the inertial range. The resulting physical picture is different from the standard one, since the enstrophy transfer is catalyzed by the large-scale motions. The theory gives some unambiguous predictions for the corrections in the inertial range.
14391150
Beyond Space-Time
These notes, based on the remarks made at the 23 Solvay Conference, collect several speculative ideas concerning gauge/ strings duality, de Sitter spaces, dimensionality and the cosmological constant.
121723234
Directions in String Theory
Strings are important objects for physics, although it has not been proved yet. It is a common hope, that they are fundamental elements of grand unification. Much less common is the hope that they describe color-electric fluxes and help to solve gluodynamics and also that they are relevant for the solution of the three-dimensional Ising model. In my talk I shall describe various topics, important for all three problems. I believe that in order to reach understanding it is useful to keep them in mind simultaneously. Unfortunately, my presentation will be fragmentary, because my understanding of the subject is far from complete.
121164015
Bulk GaAs as a solar neutrino detector
A GaAs detector may offer the unique possibility to independently study neutrino properties and solar physics. The ability to measure the flux of p–p, 7Be and pep solar neutrinos would allow one to approach a solution of the “solar neutrino problem”, i.e. the explanation of the significant deficit in observed capture rate of solar neutrinos. A large GaAs solar neutrino detector would allow to measure parameters for possible Mikheyev–Smirnov–Wolfenstein neutrino oscillations with unprecedented precision. A model-independent test for sterile neutrinos is also possible. A direct measurement of the temperature profile of the Sun center appears feasible. A GaAs detector would also provide the ability to observe neutral current interactions in addition to addressing a wide range of other interesting physics. 
 
In order to measure the p–p, pep and 7Be neutrinos a detector is required with low threshold (< 350 keV), good energy resolution (< 2 keV) and low background. A GaAs solid-state detector could meet the listed requirements. A large GaAs detector would be composed of approximately 40,000 intrinsic GaAs crystals, each weighting 3.2 kg. Such a detector would have a mass of 125 ton and would contain 60 ton of Ga occupying a volume of roughly 3 m on one side. Previous efforts by many groups have resulted in producing very small detectors with reasonably good resolution. However, it has thus far proved impossible to make large detectors with good resolution. Thus, a solar neutrino detector such as the one described above is obviously very ambitious, but the scientific motivation is sufficiently high that we have begun a research and development program with the goal of determining the technical feasibility of constructing large GaAs crystals with the requisite electronic properties to serve as particle detectors.
122608189
Study of GaAs as a material for solar neutrino detectors
Abstract Semi-insulating GaAs crystals grown by liquid encapsulated Czochralski technique from Ga-rich melts were evaluated as a possible material for radiation detectors with a high active layer thickness. The density of deep traps, particularly the midgap EL2 donors pinning the Fermi level, was measured by various techniques in conducting and semi-insulating samples. For EL2 traps, a direct evidence of their partial neutralization in the space charge region of reverse biased Schottky diodes due to nonequilibrium capture of electrons is presented for the first time. It is shown that the density of EL2 centers decreases with decreased As composition of the melt very gradually, especially for post-growth annealed samples. Subsequently, if one aims to decrease the EL2 density to such an extent that it would make a serious impact on the depletion layer width in GaAs-based detectors one has to grow semi-insulating GaAs crystals from melts with As composition below about 43% which poses a problem for the preservation of high resistivity of the material due to the relatively high concentration of compensating acceptors.