2,404 research outputs found
Positioning the Destination Product-Can Regional Tourist Boards Learn from Private Sector Practice?
This article examines the role of positioning in the
marketing of a tourism destination. The study focuses on the current positioning strategies pursued by the Regional Tourist Boards (RTBs) in England. A recent nationwide consumer research study into short holiday destination choice in the UK revealed that consumers were confused by the regional product message. The evidence suggests that current RTB positioning strategies are failing to keep pace with the constantly evolving needs of the consumer. This
article explores the reasons for clearly positioning the destination product and suggests that, although RTBs could learn from marketing strategies employed in other sectors of the tourism industry, there are likely to be organisational and cultural barriers inhibiting this
learning curve
Volume elements and torsion
We reexamine here the issue of consistency of minimal action formulation with
the minimal coupling procedure (MCP) in spaces with torsion. In Riemann-Cartan
spaces, it is known that a proper use of the MCP requires that the trace of the
torsion tensor be a gradient, , and that the modified
volume element be
used in the action formulation of a physical model. We rederive this result
here under considerably weaker assumptions, reinforcing some recent results
about the inadequacy of propagating torsion theories of gravity to explain the
available observational data. The results presented here also open the door to
possible applications of the modified volume element in the geometric theory of
crystalline defects.Comment: Revtex, 8 pages, 1 figure. v2 includes a discussion on
-symmetr
Five-Dimensional Eguchi-Hanson Solitons in Einstein-Gauss-Bonnet Gravity
Eguchi-Hanson solitons are odd-dimensional generalizations of the
four-dimensional Eguchi-Hanson metric and are asymptotic to
AdS\mathbb{Z}_p$ when the cosmological constant is either positive or
negative. We find soliton solutions to Lovelock gravity in 5 dimensions that
are generalizations of these objects.Comment: 26 pages, 11 figure
Gravitational dynamics for all tensorial spacetimes carrying predictive, interpretable and quantizable matter
Only a severely restricted class of tensor fields can provide classical
spacetime geometries, namely those that can carry matter field equations that
are predictive, interpretable and quantizable. These three conditions on matter
translate into three corresponding algebraic conditions on the underlying
tensorial geometry, namely to be hyperbolic, time-orientable and
energy-distinguishing. Lorentzian metrics, on which general relativity and the
standard model of particle physics are built, present just the simplest
tensorial spacetime geometry satisfying these conditions. The problem of
finding gravitational dynamics---for the general tensorial spacetime geometries
satisfying the above minimum requirements---is reformulated in this paper as a
system of linear partial differential equations, in the sense that their
solutions yield the actions governing the corresponding spacetime geometry.
Thus the search for modified gravitational dynamics is reduced to a clear
mathematical task.Comment: 47 pages, no figures, minor update
The Lanczos potential for Weyl-candidate tensors exists only in four dimensions
We prove that a Lanczos potential L_abc for the Weyl candidate tensor W_abcd
does not generally exist for dimensions higher than four. The technique is
simply to assume the existence of such a potential in dimension n, and then
check the integrability conditions for the assumed system of differential
equations; if the integrability conditions yield another non-trivial
differential system for L_abc and W_abcd, then this system's integrability
conditions should be checked; and so on. When we find a non-trivial condition
involving only W_abcd and its derivatives, then clearly Weyl candidate tensors
failing to satisfy that condition cannot be written in terms of a Lanczos
potential L_abc.Comment: 11 pages, LaTeX, Heavily revised April 200
Higher dimensional gravity invariant under the Poincare group
It is shown that the Stelle-West Grignani-Nardelli-formalism allows, both
when odd dimensions and when even dimensions are considered, constructing
actions for higher dimensional gravity invariant under local Lorentz rotations
and under local Poincar\`{e} translations. It is also proved that such actions
have the same coefficients as those obtained by Troncoso and Zanelli in ref.
Class. Quantum Grav. 17 (2000) 4451.Comment: 7 pages, Latex, accepted in Phys. Rev.
Black Hole Entropy and the Dimensional Continuation of the Gauss-Bonnet Theorem
The Euclidean black hole has topology . It is
shown that -in Einstein's theory- the deficit angle of a cusp at any point in
and the area of the are canonical conjugates. The
black hole entropy emerges as the Euler class of a small disk centered at the
horizon multiplied by the area of the there.These results are
obtained through dimensional continuation of the Gauss-Bonnet theorem. The
extension to the most general action yielding second order field equations for
the metric in any spacetime dimension is given.Comment: 7 pages, RevTe
Algebraic Rainich theory and antisymmetrisation in higher dimensions
The classical Rainich(-Misner-Wheeler) theory gives necessary and sufficient
conditions on an energy-momentum tensor to be that of a Maxwell field (a
2-form) in four dimensions. Via Einstein's equations these conditions can be
expressed in terms of the Ricci tensor, thus providing conditions on a
spacetime geometry for it to be an Einstein-Maxwell spacetime. One of the
conditions is that is proportional to the metric, and it has previously
been shown in arbitrary dimension that any tensor satisfying this condition is
a superenergy tensor of a simple -form. Here we examine algebraic Rainich
conditions for general -forms in higher dimensions and their relations to
identities by antisymmetrisation. Using antisymmetrisation techniques we find
new identities for superenergy tensors of these general (non-simple) forms, and
we also prove in some cases the converse; that the identities are sufficient to
determine the form. As an example we obtain the complete generalisation of the
classical Rainich theory to five dimensions.Comment: 16 pages, LaTe
Structure of Lanczos-Lovelock Lagrangians in Critical Dimensions
The Lanczos-Lovelock models of gravity constitute the most general theories
of gravity in D dimensions which satisfy (a) the principle of of equivalence,
(b) the principle of general co-variance, and (c) have field equations
involving derivatives of the metric tensor only up to second order. The mth
order Lanczos-Lovelock Lagrangian is a polynomial of degree m in the curvature
tensor. The field equations resulting from it become trivial in the critical
dimension and the action itself can be written as the integral of an
exterior derivative of an expression involving the vierbeins, in the
differential form language. While these results are well known, there is some
controversy in the literature as to whether the Lanczos-Lovelock Lagrangian
itself can be expressed as a total divergence of quantities built only from the
metric and its derivatives (without using the vierbeins) in . We settle
this issue by showing that this is indeed possible and provide an algorithm for
its construction. In particular, we demonstrate that, in two dimensions, for a doublet of functions which
depends only on the metric and its first derivatives. We explicitly construct
families of such R^j -s in two dimensions. We also address related questions
regarding the Gauss-Bonnet Lagrangian in . Finally, we demonstrate the
relation between the Chern-Simons form and the mth order Lanczos-Lovelock
Lagrangian.Comment: 15 pages, no figure
Coincident electron channeling and cathodoluminescence studies of threading dislocations in GaN
We combine two scanning electron microscopy techniques to investigate the influence of dislocations on the light emission from nitride semiconductors. Combining electron channeling contrast imaging and cathodoluminescence imaging enables both the structural and luminescence properties of a sample to be investigated without structural damage to the sample. The electron channeling contrast image is very sensitive to distortions of the crystal lattice, resulting in individual threading dislocations appearing as spots with black–white contrast. Dislocations giving rise to nonradiative recombination are observed as black spots in the cathodoluminescence image. Comparison of the images from exactly the same micron-scale region of a sample demonstrates a one-to-one correlation between the presence of single threading dislocations and resolved dark spots in the cathodoluminescence image. In addition, we have also obtained an atomic force microscopy image from the same region of the sample, which confirms that both pure edge dislocations and those with a screw component (i.e., screw and mixed dislocations) act as nonradiative recombination centers for the Si-doped c-plane GaN thin film investigated
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