The Enhancon, Multimonopoles and Fuzzy Geometry

The presentation at Strings 2000 was intended to be in two main parts, but there was only time for part one. However both parts appeared on the online proceedings, and are also included in this document. The first part concerns an exploration of the connection between the physics of the `enhancon' geometry arising from wrapping N D6-branes on the K3 manifold in Type IIA string theory and that of a charge N BPS multi-monopole. This also relates to the physics of 2+1 dimensional SU(N) gauge theory with eight supercharges. The main results uncovered by this exploration are: a) better insight into the non-perturbative geometry of the enhancon; b) the structure of the moduli space geometry, and its characterisation in terms of generalisations of an Atiyah-Hitchin-like manifold; c) the use of Nahm data to describe aspects of the geometry, showing that the enhancon locus itself has a description as a fuzzy sphere. Part two discusses the addition of extra D2-branes into the geometry. Two probe computations show the difference between the geometry as seen by D2-branes and that seen by wrapped D6-branes, and the accompanying gauge theory interpretations are discussed.Comment: 10 pages. Two figures. LaTeX, IJMP style. Contribution to proceedings of Strings 2000, held at Michigan

The superstring Hagedorn temperature in a pp-wave background

The thermodynamics of type IIB superstring theory in the maximally supersymmetric plane wave background is studied. We compute the thermodynamic partition function for non-interacting strings exactly and the result differs slightly from previous computations. We clarify some of the issues related to the Hagedorn temperature in the limits of small and large constant RR 5-form. We study the thermodynamic behavior of strings in the case of $AdS_3 \times S^3 \times T^4$ geometries in the presence of NS-NS and RR 3-form backgrounds. We also comment on the relationship of string thermodynamics and the thermodynamic behavior of the sector of Yang-Mills theory which is the holographic dual of the string theory.Comment: 22 pages, JHEP style, minor misprints corrected, some comments adde

Families of N=2 Strings

In a given 4d spacetime bakcground, one can often construct not one but a family of distinct N=2 string theories. This is due to the multiple ways N=2 superconformal algebra can be embedded in a given worldsheet theory. We formulate the principle of obtaining different physical theories by gauging different embeddings of the same symmetry algebra in the same ``pre-theory.'' We then apply it to N=2 strings and formulate the recipe for finding the associated parameter spaces of gauging. Flat and curved target spaces of both (4,0) and (2,2) signatures are considered. We broadly divide the gauging choices into two classes, denoted by alpha and beta, and show them to be related by T-duality. The distinction between them is formulated topologically and hinges on some unique properties of 4d manifolds. We determine what their parameter spaces of gauging are under certain simplicity ansatz for generic flat spaces (R^4 and its toroidal compactifications) as well as some curved spaces. We briefly discuss the spectra of D-branes for both alpha and beta families.Comment: 66+1 pages, 2 tables, latex 2e, hyperref. ver2: typos corrected, reference adde

Moduli Spaces of Instantons on the Taub-NUT Space

We present ADHM-Nahm data for instantons on the Taub-NUT space and encode these data in terms of Bow Diagrams. We study the moduli spaces of the instantons and present these spaces as finite hyperkahler quotients. As an example, we find an explicit expression for the metric on the moduli space of one SU(2) instanton. We motivate our construction by identifying a corresponding string theory brane configuration. By following string theory dualities we are led to supersymmetric gauge theories with impurities.Comment: 26 pages, 7 figure

Weighing up the evidence: The contribution of critical literature reviews to the development of practice

Over the past decade there has been increasing awareness of the importance of using sound research evidence to assist clinicians, patients and clients to make informed decisions about aspects of care. The recent drive towards promoting evidence-based healthcare has provided an added impetus, highlighting the important and unique contribution of systematic reviews to this decision-making process. This paper argues that healthcare professionals should also draw on evidence and insights derived from a broader range of research traditions rather than relying on synthesised evidence from randomised controlled trials. The potential of other types of literature is explored