433 research outputs found
Conformal field theories and compact curves in moduli spaces
We show that there are many compact subsets of the moduli space of
Riemann surfaces of genus that do not intersect any symmetry locus. This
has interesting implications for supersymmetric conformal field
theories in four dimensions.Comment: Update acknowledging recent development
A Generic Storage API
We present a generic API suitable for provision of highly generic storage
facilities that can be tailored to produce various individually customised
storage infrastructures. The paper identifies a candidate set of minimal
storage system building blocks, which are sufficiently simple to avoid
encapsulating policy where it cannot be customised by applications, and
composable to build highly flexible storage architectures. Four main generic
components are defined: the store, the namer, the caster and the interpreter.
It is hypothesised that these are sufficiently general that they could act as
building blocks for any information storage and retrieval system. The essential
characteristics of each are defined by an interface, which may be implemented
by multiple implementing classes.Comment: Submitted to ACSC 200
Report on the XBase Project
This project addressed the conceptual fundamentals of data storage,
investigating techniques for provision of highly generic storage facilities
that can be tailored to produce various individually customised storage
infrastructures, compliant to the needs of particular applications. This
requires the separation of mechanism and policy wherever possible. Aspirations
include: actors, whether users or individual processes, should be able to bind
to, update and manipulate data and programs transparently with respect to their
respective locations; programs should be expressed independently of the storage
and network technology involved in their execution; storage facilities should
be structure-neutral so that actors can impose multiple interpretations over
information, simultaneously and safely; information should not be discarded so
that arbitrary historical views are supported; raw stored information should be
open to all; where security restrictions on its use are required this should be
achieved using cryptographic techniques. The key advances of the research were:
1) the identification of a candidate set of minimal storage system building
blocks, which are sufficiently simple to avoid encapsulating policy where it
cannot be customised by applications, and composable to build highly flexible
storage architectures 2) insight into the nature of append-only storage
components, and the issues arising from their application to common storage
use-cases
Restoration of a brown trout (Salmo trutta L.) population to Loch Enoch, an acified Loch in Galloway, South-West Scotland
The authors present the findings of a restoration project in Loch Enoch in Scotland. There are historical references that brown trout was present in Loch Enoch up to the 1920s but it is believed the acidity of loch triggered the disappearance of Salmo trutta. The recent observed reduction in the acidity of L. Enoch to a level close to that found in nearby lochs with trout populations, suggested that trout might now survive in L. Enoch. For a population to survive, all stages in the life-cycle of a species must be able to develop. Accordingly, tests were undertaken, first with eggs and fry. The availability of food was also studied. In October 1994, 3,000 yearling trout of L. Grannoch origin which had been reared in a local hatchery were distributed throughout the loch. The fish population was studied from 1995-98. The authors conclude that survival of the trout population is possible if the acidity of the loch water remains low
Active architecture for pervasive contextual services
Pervasive services may be defined as services that are available to any client (anytime, anywhere). Here we focus on the software and network infrastructure required to support pervasive contextual services operating over a wide area. One of the key requirements is a matching service capable of assimilating and filtering information from various sources and determining matches relevant to those services. We consider some of the challenges in engineering a globally distributed matching service that is scalable, manageable, and able to evolve incrementally as usage patterns, data formats, services, network topologies and deployment technologies change. We outline an approach based on the use of a peer-to-peer architecture to distribute user events and data, and to support the deployment and evolution of the infrastructure itself
Active architecture for pervasive contextual services
International Workshop on Middleware for Pervasive and Ad-hoc Computing MPAC 2003), ACM/IFIP/USENIX International Middleware Conference (Middleware 2003), Rio de Janeiro, Brazil This work was supported by the FP5 Gloss project IST2000-26070, with partners at Trinity College Dublin and Université Joseph Fourier, and by EPSRC grants GR/M78403/GR/M76225, Supporting Internet Computation in Arbitrary Geographical Locations, and GR/R45154, Bulk Storage of XML Documents.Pervasive services may be defined as services that are available "to any client (anytime, anywhere)". Here we focus on the software and network infrastructure required to support pervasive contextual services operating over a wide area. One of the key requirements is a matching service capable of as-similating and filtering information from various sources and determining matches relevant to those services. We consider some of the challenges in engineering a globally distributed matching service that is scalable, manageable, and able to evolve incrementally as usage patterns, data formats, services, network topologies and deployment technologies change. We outline an approach based on the use of a peer-to-peer architecture to distribute user events and data, and to support the deployment and evolution of the infrastructure itself.Peer reviewe
Symmetry-surfing the moduli space of Kummer K3s.
A maximal subgroup of the Mathieu group M24 arises as the combined
holomorphic symplectic automorphism group of all Kummer surfaces whose Kaehler
class is induced from the underlying complex torus. As a subgroup of M24, this
group is the stabilizer group of an octad in the Golay code. To meaningfully
combine the symmetry groups of distinct Kummer surfaces, we introduce the
concepts of Niemeier markings and overarching maps between pairs of Kummer
surfaces. The latter induce a prescription for symmetry-surfing the moduli
space, while the former can be seen as a first step towards constructing a
vertex algebra that governs the elliptic genus of K3 in an M24-compatible
fashion. We thus argue that a geometric approach from K3 to Mathieu Moonshine
may bear fruit.Comment: 20 pages; minor changes; accepted for publication in the Proceedings
Volume of String-Math 201
Moduli in N=1 heterotic/F-theory duality
The moduli in a 4D N=1 heterotic compactification on an elliptic CY, as well
as in the dual F-theoretic compactification, break into "base" parameters which
are even (under the natural involution of the elliptic curves), and "fiber" or
twisting parameters; the latter include a continuous part which is odd, as well
as a discrete part. We interpret all the heterotic moduli in terms of
cohomology groups of the spectral covers, and identify them with the
corresponding F-theoretic moduli in a certain stable degeneration. The argument
is based on the comparison of three geometric objects: the spectral and cameral
covers and the ADE del Pezzo fibrations. For the continuous part of the
twisting moduli, this amounts to an isomorphism between certain abelian
varieties: the connected component of the heterotic Prym variety (a modified
Jacobian) and the F-theoretic intermediate Jacobian. The comparison of the
discrete part generalizes the matching of heterotic 5brane / F-theoretic 3brane
impurities.Comment: Latex, 26 pages. Acknowledgements adde
Recovery from disability after stroke as a target for a behavioural intervention: Results of a randomised controlled trial
Purpose: Disability following stroke is highly prevalent and is predicted by psychological variables such as control cognitions and emotions, in addition to clinical variables. This study evaluated the effectiveness of a workbook-based intervention, designed to change cognitions about control, in improving outcomes for patients and their carers. Method: At discharge, stroke patients were randomly allocated (with their carers) to a 5-week intervention (n = 103) or control (normal care: n = 100). The main outcome (at 6 months) was recovery from disability using a performance measure, with distress and satisfaction as additional outcomes. Results: The intervention group showed significantly better disability recovery, allowing for initial levels of disability, than those in the control group, F(1,201) = 5.61, p = 0.019. Groups did not differ in distress or satisfaction with care for patients or carers. The only psychological process variable improved by the intervention was Confidence in Recovery but this did not mediate the effects on recovery. Conclusions: A large proportion of intervention participants did not complete the workbook tasks. This was perhaps associated with the fairly low level of personal contact with workbook providers. The modest success of this intervention suggests that it may be possible to develop effective behavioural interventions to enhance recovery from disability in stroke patients
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