Topological Aspects of Gauge Fixing Yang-Mills Theory on S4

For an $S_4$ space-time manifold global aspects of gauge-fixing are investigated using the relation to Topological Quantum Field Theory on the gauge group. The partition function of this TQFT is shown to compute the regularized Euler character of a suitably defined space of gauge transformations. Topological properties of the space of solutions to a covariant gauge conditon on the orbit of a particular instanton are found using the $SO(5)$ isometry group of the $S_4$ base manifold. We obtain that the Euler character of this space differs from that of an orbit in the topologically trivial sector. This result implies that an orbit with Pontryagin number \k=\pm1 in covariant gauges on $S_4$ contributes to physical correlation functions with a different multiplicity factor due to the Gribov copies, than an orbit in the trivial \k=0 sector. Similar topological arguments show that there is no contribution from the topologically trivial sector to physical correlation functions in gauges defined by a nondegenerate background connection. We discuss possible physical implications of the global gauge dependence of Yang-Mills theory.Comment: 13 pages, uuencoded and compressed LaTeX file, no figure

Penrose Limits, the Colliding Plane Wave Problem and the Classical String Backgrounds

We show how the Szekeres form of the line element is naturally adapted to study Penrose limits in classical string backgrounds. Relating the "old" colliding wave problem to the Penrose limiting procedure as employed in string theory we discuss how two orthogonal Penrose limits uniquely determine the underlying target space when certain symmetry is imposed. We construct a conformally deformed background with two distinct, yet exactly solvable in terms of the string theory on R-R backgrounds, Penrose limits. Exploiting further the similarities between the two problems we find that the Penrose limit of the gauged WZW Nappi-Witten universe is itself a gauged WZW plane wave solution of Sfetsos and Tseytlin. Finally, we discuss some issues related to singularity, show the existence of a large class of non-Hausdorff solutions with Killing Cauchy Horizons and indicate a possible resolution of the problem of the definition of quantum vacuum in string theory on these time-dependent backgrounds.Comment: Some misprints corrected. Matches the version in print. To appear in Classical & Quantum Gravit

Relativistic Calogero-Moser model as gauged WZW theory

We study quantum intergrable systems of interacting particles from the point of view, proposed in our previous paper. We obtain Calogero-Moser and Sutherland systems as well their Ruijsenaars relativistic generalization by a Hamiltonian reduction of integrable systems on the cotangent bundles over semi-simple Lie algebras, their affine algebras and central extensions of loop groups respectively. The corresponding 2d field theories form a tower of deformations. The top of this tower is gauged G/G WZW model on a cylinder with inserted Wilson line in appropriate representation.Comment: 24 pages,Tex file,preprint UUITP-31/93, December 1993. Latex errors occured due to e-mail problems are eliminated in this versio

Sigma Models with N=8 Supersymmetries in 2+1 and 1+1 Dimensions

We introduce an N=8 supersymmetric extension of the Bogomolny-type model for Yang-Mills-Higgs fields in 2+1 dimensions related with twistor string theory. It is shown that this model is equivalent to an N=8 supersymmetric U(n) chiral model in 2+1 dimensions with a Wess-Zumino-Witten-type term. Further reduction to 1+1 dimensions yields N=(8,8) supersymmetric extensions of the standard U(n) chiral model and Grassmannian sigma models.Comment: 8 page

Ein optimierter Versorgungsprozess bei Patienten mit schlafbezogenen Atmungsstörungen – Pilotstudie

Background: To date, patients have been instructed in diagnostic polygraphy (PG) by a trained specialist. This process is time- and cost-intensive. In a pilot study, we tested an innovative procedure in sleep-disordered breathing (SDB) to achieve faster diagnoses and more effective referral for treatment. For this purpose, study participants had a PG device delivered at home directly from the provider. Methods: Patients self-administered the PGs independently using a manual, and, if necessary, received telephone support. After the night of recording, the device was sent back to the supplier. Diagnosis by a physician was done online via an encrypted portal. In addition, subjective satisfaction with the process was assessed using a questionnaire and PG results were compared with polysomnography (PSG) within a narrow timescale. Results: Fifty patients middle-aged (50.5 ± 13.7 years), male = 30/female = 20, with suspected SDB were included in the study. The study participants had a similar mean Apnea-Hypopnea Index (AHI; PSG) of M = 20.8 (SD 23.2) and a mean AHI measured using PG of M = 20.2 (SD 18.9) under both measurement methods. At AHI values between ≥15–30/h showed sensitivity of 88% and specificity of 91%. Conclusion: In assessing whether clinically relevant sleep apnea occurred, we found a weak to moderate match between the individual diagnostic categories of the measuring process, with the most frequent matches occurring in the highest and lowest diagnosis groups. However, these results do not allow for a prediction of feasibility in a general or multimorbid patient population because of the selective sample.Hintergrund: Die Einweisung der Patienten in die diagnostische Polygraphie wird bisher von einer medizinisch ausgebildeten Fachkraft durchgeführt. Dieser Prozess ist zeit- und ressourcenintensiv. In dieser Pilotstudie wurde ein innovativer Versorgungsweg bei schlafbezogenen Atmungsstörungen (SBAS) untersucht, um eine beschleunigte Diagnostik und effektivere Therapiezuweisung zu erreichen. Hierfür wurde den Studienteilnehmern ein Polygrafie (PG)-Gerät direkt von der versorgenden Firma nach Hause geliefert. Methodik: Der Patient legte die PG selbstständig nach einer Bedienungsanleitung an und erhielt bei Bedarf telefonische Unterstützung. Nach der Untersuchungsnacht wurde das Gerät zurückgesendet. Die ärztliche Befundung erfolgte online über ein verschlüsseltes Portal. Zusätzlich erfolgte eine Befragung zur subjektiven Zufriedenheit mit dem Ablaufprozess sowie ein Vergleich der PG-Ergebnisse mit einer zeitnahen Polysomnografie (PSG). Ergebnisse: Es wurden 50 Patienten (m = 30/w = 20) mit Verdacht auf SBAS im mittleren Alter von 50,5 ± 13,7 Jahren eingeschlossen. Die Probanden wiesen unter beiden Messverfahren einen ähnlichen mittleren Apnoe-Hypopnoe-Index (AHI) (PSG) von M = 20,8 (SD 23,2) und AHI (PG) von M = 20,2 (SD 18,9) auf. Bei AHI-Werten zwischen ≥15–30/h lag die Sensitivität bei 88 % und die Spezifität bei 91 %. Diskussion: In der Beurteilung, ob eine klinisch relevante Schlafapnoe vorliegt, zeigte sich eine eher schwache, moderate Übereinstimmung zwischen den einzelnen Diagnosekategorien der Messverfahren, wobei sich die häufigsten Übereinstimmungen in den höchsten und niedrigsten Diagnosegruppen zeigten. Die Ergebnisse lassen jedoch aufgrund der selektiven Stichprobe keine Prognosen hinsichtlich der Durchführbarkeit in einer allgemeinen oder multimorbiden Patientengruppe zu

Einstein-Rosen "Bridge" Needs Lightlike Brane Source

The Einstein-Rosen "bridge" wormhole solution proposed in the classic paper [1] does not satisfy the vacuum Einstein equations at the wormhole throat. We show that the fully consistent formulation of the original Einstein-Rosen "bridge" requires solving Einstein equations of bulk D=4 gravity coupled to a lightlike brane with a well-defined world-volume action. The non-vanishing contribution of Einstein-Rosen "bridge" solution to the right hand side of Einstein equations at the throat matches precisely the surface stress-energy tensor of the lightlike brane which automatically occupies the throat ("horizon straddling") - a feature triggered by the world-volume lightlike brane dynamics.Comment: 16 pages, added explicit expressions for pressure and energy density of the lightlike brane as well as a new paragraph in the conclusions, version to appear in Physics Letters

Lightlike Brane as a Gravitational Source of Misner-Wheeler-Type Wormhole

Consistent Lagrangian description of lightlike p-branes (LL-branes) is presented in two equivalent forms - a Polyakov-type formulation and a dual to it Nambu-Goto-type formulation. An important characteristic feature of the LL-branes is that the brane tension appears as a non-trivial additional dynamical degree of freedom. Next, properties of p=2 LL-brane dynamics (as a test brane) in D=4 Kerr or Kerr-Newman gravitational backgrounds are discussed in some detail. It is shown that the LL-brane automatically positions itself on the horizon and rotates along with the same angular velocity. Finally, a Misner-Wheeler-type of Reissner-Nordstroem wormhole is constructed in a self-consistent electrically sourceless Einstein-Maxwell system in the D=4 bulk interacting with a LL-brane. The pertinent wormhole throat is located precisely at the LL-brane sitting on the outer Reissner-Nordstroem horizon with the Reissner-Nordstroem mass and charge being functions of the dynamical LL-brane tension.Comment: improved derivation in section 4; additional comment in conclusions; results unchange

Once a feminist: Lynne Segal on Grace Paley’s The Little Disturbances of Man

The following contributions came in response to a request, sent to a number of key figures in feminism today, to write on a text that had been formative for their thinking as feminists. The chosen text could be a theory, a novel, an artwork, a performance, a poem: one that had stimulated, or even revolutionised, their ideas. As we hoped, this project has created a selection of texts central to our many and different experiences as feminists. I used to say that Margaret Drabble's The Garrick Year was the story of my life, in my early twenties, as if I was just a creature of time and circumstance. I read The Garrick Year sometime between October 1965, when my first child was born, and the end of 1967, before my marriage disintegrated. Like the heroine Emma Evans, I married a successful actor, had a child, and followed his career—which in the novel led Emma to Hereford for a summer season of plays

Macro-Micro linkages and the Role of Mechanisms in Social Stratification Research

This article explores the role of theory-building in social stratification research, a sub-field of sociology whose theoretical development has not kept pace with methodological, statistical, and empirical advancements. In particular, the article proposes a new conceptual framework based on social mechanisms and the multileveled nature of the stratification process. Conceptual frameworks, which map out general principles of social organisation and social processes, are useful in guiding researchers' choice of methods and research resign. The authors argue that the identification of social mechanisms needs to be a core aspect of sociological explanation, and thus integrated into the conceptual frameworks researchers use. They apply social mechanisms to a conception of social change involving micro-to-macro linkages. The resulting conceptual framework is then applied to stratification research, where the authors observe that the micro-to-macro linkage is one of the least explored, and also one of the most promising, areas of future research, particularly for areas of the world undergoing rapid social transformation