2,170 research outputs found
The W_N minimal model classification
We first rigourously establish, for any N, that the toroidal modular
invariant partition functions for the (not necessarily unitary) W_N(p,q)
minimal models biject onto a well-defined subset of those of the SU(N)xSU(N)
Wess-Zumino-Witten theories at level (p-N,q-N). This permits considerable
simplifications to the proof of the Cappelli-Itzykson-Zuber classification of
Virasoro minimal models. More important, we obtain from this the complete
classification of all modular invariants for the W_3(p,q) minimal models. All
should be realised by rational conformal field theories. Previously, only those
for the unitary models, i.e. W_3(p,p+1), were classified. For all N our
correspondence yields for free an extensive list of W_N(p,q) modular
invariants. The W_3 modular invariants, like the Virasoro minimal models, all
factorise into SU(3) modular invariants, but this fails in general for larger
N. We also classify the SU(3)xSU(3) modular invariants, and find there a new
infinite series of exceptionals.Comment: 25 page
National and Regional Estimates of the Prevalence of Opiate and/or Crack Cocaine use 2008-09: A summary of key findings
<p>This report summarises the results of a follow-up study
to a three year project to estimate the prevalence of
‘problem drug use’ (defined as use of opiates and/or
crack cocaine) nationally (England only), regionally and
locally. The follow-up was carried out two years after the
final sweep of the original project, so could therefore
be considered as ‘sweep 5’. An overview of the national
and regional estimates are presented in this report, as are
comparisons with the estimates produced by the third
(2006-07) sweep of the study. Estimates for 2007-08 are
not available as a study was not commissioned for that
year.</p>
<p>Information about the number of people who use illicit
drugs such as heroin, other opiates or crack cocaine
is key to formulating effective policies for tackling
drug-related harm as these drugs are associated with
the highest levels of harm. It also helps inform service
provision at the local level and provides a context
in which to understand the population impact of
interventions to reduce drug-related harm.</p>
<p>Direct enumeration of those engaged in a largely covert
activity such as the use of class A drugs is difficult
and standard household survey techniques tend to
underestimate the extent of such activity. Indirect
techniques making use of various data sources offer a
more reliable way of calculating prevalence estimates for
the use of opiates and/or crack cocaine. The estimates
presented in this report are derived using two indirect
measurement techniques: the capture-recapture
method (CRC ); and the multiple indicator (MIM ) method.
These methods are described in detail in Hay et al., 2006
and Hay et al., 2007a. Methodological developments
throughout the course of the previous three sweeps are
discussed elsewhere (Hay et al., 2007b, Hay et al., 2008).
The individuals covered by this study were people aged
15 to 64 and resident in each DAT area, and known to
be using heroin, methadone, other opiate drugs or
crack cocaine.</p>
Political risk in light rail transit PPP projects
Since 2003 public-private partnerships (PPPs) have
represented between 10 and 13.5% of the total investment
in public services in the UK. The macro-economic and
political benefits of PPPs were among the key drivers for
central government's decision to promote this form of
procurement to improve UK public services. Political
support for a PPP project is critical and is frequently cited as the most important critical success factor. This paper investigates the significance of political support and reviews the treatment of political risk in a business case by the public sector project sponsor for major UK-based light rail transit PPP projects during their development stage. The investigation demonstrates that in the early project stages it is not traditional quantitative Monte Carlo risk analysis that is important; rather it is the identification and representation of political support within a business case together with an understanding of how this information is then used to inform critical project decisions
Can a Lattice String Have a Vanishing Cosmological Constant?
We prove that a class of one-loop partition functions found by Dienes, giving
rise to a vanishing cosmological constant to one-loop, cannot be realized by a
consistent lattice string. The construction of non-supersymmetric string with a
vanishing cosmological constant therefore remains as elusive as ever. We also
discuss a new test that any one-loop partition function for a lattice string
must satisfy.Comment: 14 page
On the Classification of Diagonal Coset Modular Invariants
We relate in a novel way the modular matrices of GKO diagonal cosets without
fixed points to those of WZNW tensor products. Using this we classify all
modular invariant partition functions of
for all positive integer level , and for all and infinitely many (in fact, for
each a positive density of ). Of all these classifications, only that
for had been known. Our lists include many
new invariants.Comment: 24 pp (plain tex
Health care utilisation amongst older adults with sensory and cognitive impairments in Europe.
Worldwide, the high prevalence of multiple chronic conditions amongst older population has led to increased utilisation of health care and rising associated costs, becoming a major public health concern. Hearing, vision and cognitive disorders are common chronic conditions amongst older Europeans and recent studies have documented its high co-occurrence. While it has been shown separately that suffering either mental disorders or sensory (hearing and vision) impairments is associated with higher health care utilisation, the association between health care utilisation and the interaction of these conditions has received little attention in the literature. Therefore, using four waves of the Survey of Health, Ageing and Retirement in Europe (SHARE), this study applies the correlated random effects method to the negative binomial and finite mixture models to analyse the extent to which the interaction of cognitive and sensory impairments is associated with health care use. We found that individuals with cognitive impairment tend to have more hospitalisations. The finite mixture approach indicates a positive association between sensory impairment and the number of hospitalisations amongst low users of health care. Additionally, our findings suggest a positive association between suffering both impairments at the same time and the number of doctor and GP visits
Multi-physics energy approach and demonstration facility
A methodology to investigate the generation, transport and storage of energy based on a multi-physics approach, tied to the end use application, is presented. Often little or no consideration is given to the end use or desired product of the energy used. Current energy generation, transport and storage are dominated heavily by a few large sectors, notably electricity and hydrocarbons. These are very effective and practical systems that facilitate the delivery of vast amounts of energy. It is then not surprising that most strategies for renewable energy generation and storage revolve around this centralized model in some way. In larger scale generation, power is usually fed onto the electrical grid with a current challenge being grid stabilization with increasing penetration of intermittent renewable resources. In small grid-independent system a mix of battery and hydrocarbon storage are often used to keep a micro-
grid available for various end use applications.
A paradigm shift in the thinking and design of energy systems based on the required end use or
product is needed. The philosophy and motivation that lead to the consideration of this new
approach are outlined in this article. Following this a summary of a methodical approach to
developing the most energy and cost-effective solution to general processes by considering their
end-use physics is presented. Examples of innovative energy generation, storage, and transport
solutions based on the multi-physics approach are then outlined. Finally, a brief description of
the Multi-physics Renewable Energy Lab (MPREL), a demonstration facility based on the approach and
currently under construction at the Naval Postgraduate School, is given
On parity functions in conformal field theories
We examine general aspects of parity functions arising in rational conformal
field theories, as a result of Galois theoretic properties of modular
transformations. We focus more specifically on parity functions associated with
affine Lie algebras, for which we give two efficient formulas. We investigate
the consequences of these for the modular invariance problem.Comment: 18 pages, no figure, LaTeX2
Lie group weight multiplicities from conformal field theory
Dominant weight multiplicities of simple Lie groups are expressed in terms of
the modular matrices of Wess-Zumino-Witten conformal field theories, and
related objects. Symmetries of the modular matrices give rise to new relations
among multiplicities. At least for some Lie groups, these new relations are
strong enough to completely fix all multiplicities.Comment: 12 pages, Plain TeX, no figure
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