1,030 research outputs found
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
Charges of Exceptionally Twisted Branes
The charges of the exceptionally twisted (D4 with triality and E6 with charge
conjugation) D-branes of WZW models are determined from the microscopic/CFT
point of view. The branes are labeled by twisted representations of the affine
algebra, and their charge is determined to be the ground state multiplicity of
the twisted representation. It is explicitly shown using Lie theory that the
charge groups of these twisted branes are the same as those of the untwisted
ones, confirming the macroscopic K-theoretic calculation. A key ingredient in
our proof is that, surprisingly, the G2 and F4 Weyl dimensions see the simple
currents of A2 and D4, respectively.Comment: 19 pages, 2 figures, LaTex2e, complete proofs of all statements,
updated bibliograph
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
Averaging and sampling for magnetic-observatory hourly data
A time and frequency-domain analysis is made of the effects of averaging and
sampling methods used for constructing magnetic-observatory hourly data
values. Using 1-min data as a proxy for continuous, geomagnetic variation,
we construct synthetic hourly values of two standard types: instantaneous
"spot" measurements and simple 1-h "boxcar" averages. We compare these
average-sample types with others: 2-h average, Gaussian, and "brick-wall"
low-frequency-pass. Hourly spot measurements provide a statistically unbiased
representation of the amplitude range of geomagnetic-field variation, but as
a representation of continuous field variation over time, they are
significantly affected by aliasing, especially at high latitudes. The 1-h,
2-h, and Gaussian average-samples are affected by a combination of amplitude
distortion and aliasing. Brick-wall values are not affected by either
amplitude distortion or aliasing, but constructing them is, in an operational
setting, relatively more difficult than it is for other average-sample types.
It is noteworthy that 1-h average-samples, the present standard for
observatory hourly data, have properties similar to Gaussian average-samples
that have been optimized for a minimum residual sum of amplitude distortion
and aliasing. For 1-h average-samples from medium and low-latitude
observatories, the average of the combination of amplitude distortion and
aliasing is less than the 5.0 nT accuracy standard established by Intermagnet
for modern 1-min data. For medium and low-latitude observatories, average
differences between monthly means constructed from 1-min data and monthly
means constructed from any of the hourly average-sample types considered here
are less than the 1.0 nT resolution of standard databases. We recommend that
observatories and World Data Centers continue the standard practice of
reporting simple 1-h-average hourly values
Application of LANDSAT to the surveillance of lake eutrophication in the Great Lakes basin
The author has identified the following significant results. A step-by-step procedure for establishing and monitoring the trophic status of inland lakes with the use of LANDSAT data, surface sampling, laboratory analysis, and aerial observations were demonstrated. The biomass was related to chlorophyll-a concentrations, water clarity, and trophic state. A procedure was developed for using surface sampling, LANDSAT data, and linear regression equations to produce a color-coded image of large lakes showing the distribution and concentrations of water quality parameters, causing eutrophication as well as parameters which indicate its effects. Cover categories readily derived from LANDSAT were those for which loading rates were available and were known to have major effects on the quality and quantity of runoff and lake eutrophication. Urban, barren land, cropland, grassland, forest, wetlands, and water were included
The charges of a twisted brane
The charges of the twisted D-branes of certain WZW models are determined. The
twisted D-branes are labelled by twisted representations of the affine algebra,
and their charge is simply the ground state multiplicity of the twisted
representation. It is shown that the resulting charge group is isomorphic to
the charge group of the untwisted branes, as had been anticipated from a
K-theory calculation. Our arguments rely on a number of non-trivial Lie
theoretic identities.Comment: 27 pages, 1 figure, harvmac (b
On fusion algebra of chiral models
We discuss some algebraic setting of chiral models in terms of
the statistical dimensions of their fields. In particular, the conformal
dimensions and the central charge of the chiral models are
calculated from their braid matrices. Futhermore, at level K=2, we present the
characteristic polynomials of their fusion matrices in a factored form.Comment: 11 pages, ioplpp
Branching rules of semi-simple Lie algebras using affine extensions
We present a closed formula for the branching coefficients of an embedding p
in g of two finite-dimensional semi-simple Lie algebras. The formula is based
on the untwisted affine extension of p. It leads to an alternative proof of a
simple algorithm for the computation of branching rules which is an analog of
the Racah-Speiser algorithm for tensor products. We present some simple
applications and describe how integral representations for branching
coefficients can be obtained. In the last part we comment on the relation of
our approach to the theory of NIM-reps of the fusion rings of WZW models with
chiral algebra g_k. In fact, it turns out that for these models each embedding
p in g induces a NIM-rep at level k to infinity. In cases where these NIM-reps
can be be extended to finite level, we obtain a Verlinde-like formula for
branching coefficients.Comment: 11 pages, LaTeX, v2: one reference added, v3: Clarified proof of
Theorem 2, completely rewrote and extended Section 5 (relation to CFT), added
various references. Accepted for publication in J. Phys.
D-brane charges on non-simply connected groups
The maximally symmetric D-branes of string theory on the non-simply connected
Lie group SU(n)/Z_d are analysed using conformal field theory methods, and
their charges are determined. Unlike the well understood case for simply
connected groups, the charge equations do not determine the charges uniquely,
and the charge group associated to these D-branes is therefore in general not
cyclic. The precise structure of the charge group depends on some number
theoretic properties of n, d, and the level of the underlying affine algebra k.
The examples of SO(3)=SU(2)/Z_2 and SU(3)/Z_3 are worked out in detail, and the
charge groups for SU(n)/Z_d at most levels k are determined explicitly.Comment: 31 pages, 1 figure. 2 refs added. Added the observation: the charge
group for each su(2) theory equals the centre of corresponding A-D-E grou
The fusion algebra of bimodule categories
We establish an algebra-isomorphism between the complexified Grothendieck
ring F of certain bimodule categories over a modular tensor category and the
endomorphism algebra of appropriate morphism spaces of those bimodule
categories. This provides a purely categorical proof of a conjecture by Ostrik
concerning the structure of F.
As a by-product we obtain a concrete expression for the structure constants
of the Grothendieck ring of the bimodule category in terms of endomorphisms of
the tensor unit of the underlying modular tensor category.Comment: 16 page
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