Taub-NUT dyons in heterotic string theory.
Starting with the Taub--NUT solution to Einstein's equations, together with a constant dilaton, a dyonic Taub--NUT solution of low energy heterotic string theory with non--trivial dilaton, axion and $U(1)$ gauge fields is constructed by employing $O(1,1)$ transformations. The electromagnetic dual of this solution is constructed, using $SL(2,\rline)$ transformations. By an appropriate change to scaled variables, the extremal limit of the dual solution is shown to correspond to the low energy limit of an exact conformal field theory presented previously.

title: Is string theory a theory of strings
abstract: Recently a great deal of evidence has been found indicating that type IIA string theory compactified on K 3 is equivalent to heterotic string theory compactified on T 4 . Under the transformation which relates the two theories, the roles of fundamental and solitonic string solutions are interchanged. We show that there exists a solitonic membrane solution of the heterotic string theory which becomes a singular solution of the type IIA theory, and should therefore be interpreted as a fundamental membrane in the latter theory. We speculate upon the implications that the complete type IIA theory is a theory of membranes, as well as strings.

title: Global Currents, Phase Transitions, and Chiral Symmetry Breaking in Large N_c Gauge Theory
abstract: We study, using a gravity dual, the finite temperature dynamics of $SU(N_c)$ gauge theory for large $N_c$, with fundamental quark flavours in a quenched approximation, in the presence of a fixed R--charge under a global R--current. We observe several notable phenomena. There is a first order phase transition where the quark condensate jumps discontinuously at finite quark mass, generalizing similar transitions seen at zero charge. Our tool in these studies is holography, the string dual of the gauge theory being the geometry of $N_c$ spinning D3--branes at finite temperature, probed by a D7--brane.

title: String Theory Without Branes
abstract: We present a class of solvable models that resemble string theories in many respects but have a strikingly different non-perturbative sector. In particular, there are no exponentially small contributions to perturbation theory in the string coupling, which normally are associated with branes and related objects. Perturbation theory is no longer an asymptotic expansion, and so can be completely re-summed to yield all the non-perturbative physics. We examine a number of other properties of the theories, for example constructing and examining the physics of loop operators, which can be computed exactly, and gain considerable understanding of the difference between these new theories and the more familiar ones, including the possibility of how to interpolate between the two types. Interestingly, the models we exhibit contain a family of zeros of the partition function which suggest a novel phase structure. The theories are defined naturally by starting with models that yield well-understood string theories and allowing a flux-like background parameter to take half-integer rather than integer values. The family of models thus obtained are seeded by functions that are intimately related to the classic rational solutions of the Painleve II equation, and a family of generalisations.

title: String theory and water waves
abstract: We uncover a remarkable role that an infinite hierarchy of nonlinear differential equations plays in organizing and connecting certain string theories non-perturbatively. We are able to embed the type 0A and 0B (A, A) minimal string theories into this single framework. The string theories arise as special limits of a rich system of equations underpinned by an integrable system known as the dispersive water wave hierarchy. We observe that there are several other string-like limits of the system, and conjecture that some of them are type IIA and IIB (A, D) minimal string backgrounds. We explain how these and several string-like special points arise and are connected. In some cases, the framework endows the theories with a non-perturbative definition for the first time. Notably, we discover that the Painlev? IV equation plays a key role in organizing the string theory physics, joining its siblings, Painlev? I and II, whose roles have previously been identified in this minimal string context.

title: Holography, thermodynamics, and fluctuations of charged AdS black holes
abstract: The physical properties of Reissner-Nordstrom black holes in (n11)-dimensional anti-de Sitter spacetime are related, by a holographic map, to the physics of a class of n-dimensional field theories coupled to a background global current. Motivated by that fact, and the recent observations of the striking similarity between the thermodynamic phase structure of these black holes ~in the canonical ensemble! and that of the van der Waals-Maxwell liquid-gas system, we explore the physics in more detail. We study fluctuations and stability within the equilibrium thermodynamics, examining the specific heats and electrical permittivity of the holes, and consider the analogue of the Clayperon equation at the phase boundaries. Consequently, we refine the phase diagrams in the canonical and grand canonical ensembles. We study the interesting physics in the neighborhood of the critical point in the canonical ensemble. There is a second order phase transition found there, and that region is characterized by a Landau-Ginzburg model with A3 potential. The holographically dual field theories provide the description of the microscopic degrees of freedom which underlie all of the thermodynamics, as can be seen by examining the form of the microscopic fluctuations. @S0556-2821~99!06820-4#

title: Low-energy technicolor Lagrangian with vector mesons.
abstract: We apply techniques used in QCD and the implied chiral symmetry to motivate a low-energy Lagrangian for technicolor theories. This allows one to cleanly introduce the gluon and the weak gauge bosons at the technifermion level. The Higgs mechanism and techni-vector-meson dominance are displayed. The effect of vector dominance on the {ital W} and {ital Z} masses, the techni-{omega} and techni-{rho} couplings, and the sizable enhancement by the latter on {ital W} and {ital Z} production are demonstrated. Differences between our results and some published results are discussed. The incorporation of extended technicolor interactions is also presented.

title: Energy dependence of pion inelastic scattering to the 1(+) states in 12C.
abstract: The energy dependence of cross sections for inelastic pion scattering to the /Delta/ = /Delta/ = /Delta/ = 1 transition at 15.11 MeV in /sup 12/C is found to map very closely the /Delta/ = /Delta/ = /Delta/+1 /pi/-nucleon scattering cross sections at beam energies from 50 to 295 MeV. This free /pi/-nucleon energy dependence is due to the prominent /Delta/sub 3/2,3/2/ resonance, corresponding to the first excited nucleon state, which is mirrored in the /pi/-nucleus system with little alteration.

title: Constraints on bag formation from the scalar sector.

title: Massive hadron pair production by 800 GeV/c protons on nuclear targets.
abstract: We report data on proton-nucleon collisions obtained on Fermilab experiment E711, in which high transverse momentum hadrons are produced near 90[degree] in the proton-nucleon center of mass forming high mass states, using an 800 GeV/[ital c] proton beam on targets of beryllium, aluminum, iron, and tungsten. The data presented cover the mass range from 7 to 15 GeV/[ital c][sup 2], the three dihadron charge states ++, +[minus], and [minus][minus], and parton-parton scattering angles up to cos[theta][sup *]=0.50. We present the differential mass dihadron cross section, as well as the angular and charge dependence of the measurement. The cross section as a function of the parton-parton scattering angle for the three charge states is shown to vary linearly with the value of the atomic weight. While the angular distributions are shown to be independent of the target type, a small dependence on the charge state of the distributions is observed. The data are shown to be in good agreement with extrapolations from previous measurements and phenomenological QCD calculations.

title: Fritzsch-Stech model in SO(10).
abstract: The combined Fritzsch-Stech model for quarks is consistent with our present knowledge of quark masses and mixing angles. A possible way to extend it to leptons: by using an SO(10) framework: has been suggested by Bottino, Kim, Nishiura, and Sze. We investigate this model further and find some new features. It is first noted that the allowed quark masses are somewhat sensitive to the experimental uncertainties in the input parameters. This is carefully analyzed and we find that the original Stech Ansatz for the hadron sector is consistent. However, if the top-quark mass is greater than about 45 GeV, this Ansatz must be slightly modified. It is found that in a model of the present type the seesaw mechanism for neutrino masses may be drastically modified. This occurs because in SO(10) it is likely that the matrix of heavy ''right-handed'' neutrinos is close to a singular matrix. This feature is analyzed both analytically and numerically. Various patterns involving two extremely light neutrinos and one intermediate-mass (order of several MeV) neutrino which may arise are compared with experiment. More orthodox and perhaps more probable patterns for neutrino masses are also discussed. The lepton-mixing matrices are predicted and the results support recentmore » explanations of the solar-neutrino paradox.« less