Exact ground state and kink-like excitations of a two dimensional Heisenberg antiferromagnet

A rare example of a two dimensional Heisenberg model with an exact dimerized ground state is presented. This model, which can be regarded as a variation on the kagome lattice, has several features of interest: it has a highly (but not macroscopically) degenerate ground state; it is closely related to spin chains studied by earlier authors; in particular, it is probably the first genuinely two-dimensional quantum system to exhibit domain-wall-like ``kink'' excitations normally found only in one-dimensional systems. In some limits it decouples into non-interacting chains, purely dynamically and not because of weakening of interchain couplings: indeed, paradoxically, this happens in the limit of strong coupling of the chains.Comment: 4 pages, revtex, 5 figures included via epsfi

Charged Dilaton Black Holes with Unusual Asymptotics

We present a new class of black hole solutions in Einstein-Maxwell-dilaton gravity in $n \ge 4$ dimensions. These solutions have regular horizons and a singularity only at the origin. Their asymptotic behavior is neither asymptotically flat nor (anti-) de Sitter. Similar solutions exist for certain Liouville-type potentials for the dilaton.Comment: 24 pages, harvmac.tex, no figure

Output state in multiple entanglement swapping

The technique of quantum repeaters is a promising candidate for sending quantum states over long distances through a lossy channel. The usual discussions of this technique deals with only a finite dimensional Hilbert space. However the qubits with which one implements this procedure will "ride" on continuous degrees of freedom of the carrier particles. Here we analyze the action of quantum repeaters using a model based on pulsed parametric down conversion entanglement swapping. Our model contains some basic traits of a real experiment. We show that the state created, after the use of any number of parametric down converters in a series of entanglement swappings, is always an entangled (actually distillable) state, although of a different form than the one that is usually assumed. Furthermore, the output state always violates a Bell inequality.Comment: 11 pages, 6 figures, RevTeX

Cost-benefit analysis of introducing next-generation sequencing (metagenomic) pathogen testing in the setting of pyrexia of unknown origin

Pyrexia of unknown origin (PUO) is defined as a temperature of >38.3°C that lasts for >3 weeks, where no cause can be found despite appropriate investigation. Existing protocols for the work-up of PUO can be extensive and costly, motivating the application of recent advances in molecular diagnostics to pathogen testing. There have been many reports describing various analytical methods and performance of metagenomic pathogen testing in clinical samples but the economics of it has been less well studied. This study pragmatically evaluates the feasibility of introducing metagenomic testing in this setting by assessing the relative cost of clinically-relevant strategies employing this investigative tool under various cost and performance scenarios using Singapore as a demonstration case, and assessing the price and performance benchmarks, which would need to be achieved for metagenomic testing to be potentially considered financially viable relative to the current diagnostic standard. This study has some important limitations: we examined only impact of introducing the metagenomic test to the overall diagnostic cost and excluded costs associated with hospitalization and makes assumptions about the performance of the routine diagnostic tests, limiting the cost of metagenomic test, and the lack of further work-up after positive pathogen detection by the metagenomic test. However, these assumptions were necessary to keep the model within reasonable limits. In spite of these, the simplified presentation lends itself to the illustration of the key insights of our paper. In general, we find the use of metagenomic testing as second-line investigation is effectively dominated, and that use of metagenomic testing at first-line would typically require higher rates of detection or lower cost than currently available in order to be justifiable purely as a cost-saving measure. We conclude that current conditions do not warrant a widespread rush to deploy metagenomic testing to resolve any and all uncertainty, but rather as a front-line technology that should be used in specific contexts, as a supplement to rather than a replacement for careful clinical judgement

Selecting Resort Locations

[[abstract]]This study examines a comprehensive and objective three-stage method for selecting resort location in Taiwan that maximize competitive advantage. The factors and criteria used in the evaluation model are obtained from an exhaustive literature review and interviews with 16 experts. In the first stage, for which the modified Delphi method is used to identify the evaluation criteria, a survey is performed to rank the relative importance of the 22 criteria identified in the interviews. In the second stage, 19 experts evaluate potential resort locations using a subjective multi-criteria model, the analytical hierarchy process (AHP). The analytical results yield rankings of resorts of the following types: casino resorts, seaside resorts, health/spa resorts and lakeside resorts. In the final stage, a sensitivity analysis is performed to clarify the strength of the various influences on resort selection. The analytical results are used to develop and examine a potential solution.[[journaltype]]國外[[incitationindex]]SSCI[[booktype]]紙本[[countrycodes]]GB

‘As a woman…’; ‘As a Muslim…’: Subjects, positions and counter-terrorism powers in the United Kingdom

This article presents findings from original focus group research on the importance of identity claims within public understandings of counter-terrorism across the UK. Following a review of existing literature on the terrorism/counter-terrorism/identity nexus, the article introduces four prominent subject positions inhabited within public articulations of counter-terrorism powers: the ‘Muslim’, the ‘target’, the ‘woman’ and the ‘unaffected’. Positions such as these, we argue, both enable and inhibit particular normative, political and anecdotal claims about counter-terrorism frameworks and their impact upon the body politic. This, we suggest, is demonstrative of the co-constitutive role between counter-terrorism and identity claims. Thus, on the one hand, counter-terrorism initiatives work to position individuals socially, politically, and culturally: (re)producing various religious, ethnic and other identities. Yet, at the same time, specific subject positions are integral to the articulation of people’s attitudes toward developments in counter-terrorism. The article concludes by thinking through some of the implications of this, including for resistance toward securitising moves and for citizenship more generally

Markets and marketing research on poverty and its alleviation: Summarizing an evolving logic toward human capabilities, well-being goals and transformation

Marketing practitioners and business scholars now view some of the world’s poorest communities as profitable growth markets. Hence a market-based approach to poverty alleviation has gathered momentum. This article traces the evolution of such a market-based approach over four decades and highlights a gradual trend away from a deficit-reduction approach (focused on constraints and justice) towards an opportunity-expansion approach (focused on capabilities and well-being). This trend is summarized in an analytical framework of human capabilities, well-being goals and transformative impact evolved from the literature. The framework is then used to analyse the practice of sanitation marketing, which has emerged as a key method in one of the highest priority domains in international development discourse – sanitation. The article concludes with a discussion of how contemporary work can further take forward the key tenets of the framework and guide the development of ‘good markets’ for the poor

Many body physics from a quantum information perspective

The quantum information approach to many body physics has been very successful in giving new insight and novel numerical methods. In these lecture notes we take a vertical view of the subject, starting from general concepts and at each step delving into applications or consequences of a particular topic. We first review some general quantum information concepts like entanglement and entanglement measures, which leads us to entanglement area laws. We then continue with one of the most famous examples of area-law abiding states: matrix product states, and tensor product states in general. Of these, we choose one example (classical superposition states) to introduce recent developments on a novel quantum many body approach: quantum kinetic Ising models. We conclude with a brief outlook of the field.Comment: Lectures from the Les Houches School on "Modern theories of correlated electron systems". Improved version new references adde