Taming the supergravity description of non-BPS D-branes: the D/Dbar solution

We obtain the supergravity solution which describes a bound state of D-string/anti-D-string pairs attached to different fixed planes of an orbifold, in type IIB string theory compactified on T^4/Z_2. For parameters at which the conformal field theory point of view predicts stability, the solution displays a repulson-like singularity. However, we observe that a D-string/anti-D-string pair probe in this background becomes tensionless before reaching the singularity, suggesting a resolution by the enhancon mechanism. Moreover, the force feels by this probe is attractive, in contrast to the repulsive behaviour observed in the non-BPS D-brane description.Comment: 21 pages, Latex, uses JHEP.cls. Substantial revision; in particular, clarification of the two T-dual descriptions in section 2 and improved discussion of the enhancon mechanism in section 4. Published versio

Effective Action of Matter Fields in Four-Dimensional String Orientifolds

We study various aspects of the Kahler metric for matter fields in N=1,2 orientifold compactifications of type IIB string theory. The result has an infrared-divergent part which reproduces the field- theoretical anomalous dimensions, and a moduli-dependent part which comes from N=2 sectors of the orientifold. For the N=2 orientifolds, we also compute the disk amplitude for two matter fields on the boundary and a twisted closed string modulus in the bulk. Our results are in agreement with supersymmetry: the singlet under the SU(2)_R R-symmetry has vanishing coupling, while the coupling of the SU(2)_R triplet does not vanish.Comment: 24 pages, JHEP LaTex, no figures, v2: references added, typos correcte

Curvature terms in D-brane actions and their M-theory origin

We derive the complete $(curvature)^2$ terms of effective D-brane actions, for arbitrary ambient geometries and world-volume embeddings, at lowest order (disk-level) in the string-loop expansion. These terms reproduce the $o(\alpha'^2)$ corrections to string scattering amplitudes, and are consistent with duality conjectures. In the particular case of the D3-brane with trivial normal bundle, considerations of $SL(2,\mathbb{Z})$ invariance lead to a complete sum of D-instanton corrections for both the parity-conserving and the parity-violating parts of the effective action. These corrections are required for the cancellation of the modular anomalies of massless modes, and are consistent with the absence of chiral anomalies in the intersection domain of pairs of D-branes. We also show that the parity-conserving part of the non-perturbative R^2 action follows from a one-loop quantum calculation in the six-dimensional world-volume of the M5-brane compactified on a two-torus.Comment: tex file, 31 pages, uses harvmac. Some rewriting of section 2, conclusions and appendix B, in particular in what concerns the discussion of seven-branes in the conclusions and the structure of $\alpha'^2$ terms in appendix B. Other minor corrections plus added reference

Zero leakage design for ducts and tube connections for deep space travel. Volume 5 - Tube connector design principles and evaluation Final report, 5 Jul. 1963 - 30 Jun. 1967

Principles of connector testing, design evaluation of commercial connectors, and assessment of design rules for threaded connector

A randomised controlled trial evaluating the use of polyglactin (Vicryl) mesh, polydioxanone (PDS) or polyglactin (Vicryl) sutures for pelvic organ prolapse surgery : outcomes at 2 years

Peer reviewedPostprin

Taylorism, targets and the pursuit of quantity and quality by call centre management

The paper locates the rise of the call centre within the context of the development of Taylorist methods and technological change in office work in general. Managerial utilisation of targets to impose and measure employees' quantitative and qualitative performance is analysed in four case-study organisations. The paper concludes that call centre work reflects a pardigmic re-configuration of customer servicing operations, and that the continuing application of Taylorist methods appears likely