1,310 research outputs found
News vs Information
We consider the relative entropy between the vacuum state and a coherent
state in linearized quantum gravity around a stationary black hole spacetime.
Combining recent results by Casini et al. and Longo with the Raychaudhuri
equation, the following result is obtained: Let be the algebra of
observables assoiciated with a region that is the causal future of some compact
set in the interior of the spacetime. Let be the relative entropy with
respect to this algebra, the area of the horizon cross section defined by
the region, computed to second order in the gravitational perturbation. If the
region is time-translated by the Killing parameter , then , with the flux of the gravitational/matter radiation
(integrated squared news tensor) emitted towards the future of the region.Comment: 11 pages, 1 figure. arXiv admin note: text overlap with
arXiv:1903.07508, v2: some details added on function spaces and decay of
solutions, refs. adde
The implementation of manufacturing concepts in a non-traditional manufacturing environment.
This thesis is the result of a two year Teaching Company Programme between Middlesex University and Tony Stone Images in which basic manufacturing philosophy has been applied to an arts based Company.
Various techniques were used including flowcharts, a production simulation package and a critical path analysis to determine the production lead time of a photographic transparency to three possible destinations. On identifying the processes involved a series of smaller projects were undertaken to remove the non-value adding elements. In some cases this resulted in some quite large changes occurring in the Company; one being to move departmental locations in the building to better reflect the flow of work through the organisation.
Once improvements had been made a System was installed which allows accurate tracking of the images through the processes in terms of their volume, location and routing history. This has provided valuable information on image processing by giving a more realistic figure for production lead time rather than the senior managers relying on a 'best guess' for each department. The System became known as the Workflow System and its development and installation was divided into two phases. This thesis covers phase one.
One of the most important issues arising from the project is the fact that the Company has grown so rapidly over the last few years it has become unable to change culture and operating policy to meet the demands of the customer or competition. The conflict between image quality and image volume needs to be conquered in order to allow production to be more scientifically measured and controlled to provide an efficient manufacturing lead time to satisfy market needs. The Workflow System has provided the foundations upon which this measurement and control can be built
Comparison between various notions of conserved charges in asymptotically AdS-spacetimes
We derive hamiltionian generators of asymptotic symmetries for general
relativity with asymptotic AdS boundary conditions using the ``covariant phase
space'' method of Wald et al. We then compare our results with other
definitions that have been proposed in the literature. We find that our
definition agrees with that proposed by Ashtekar et al, with the spinor
definition, and with the background dependent definition of Henneaux and
Teitelboim. Our definition disagrees with the one obtained from the
``counterterm subtraction method,'' but the difference is found to consist only
of a ``constant offset'' that is determined entirely in terms of the boundary
metric. We finally discuss and justify our boundary conditions by a linear
perturbation analysis, and we comment on generalizations of our boundary
conditions, as well as inclusion of matter fields.Comment: 64p, Latex, no figures, v2: references added, typos corrected, v3:
some equations correcte
From SO/Sp instantons to W-algebra blocks
We study instanton partition functions for N=2 superconformal Sp(1) and SO(4)
gauge theories. We find that they agree with the corresponding U(2) instanton
partitions functions only after a non-trivial mapping of the microscopic gauge
couplings, since the instanton counting involves different renormalization
schemes. Geometrically, this mapping relates the Gaiotto curves of the
different realizations as double coverings. We then formulate an AGT-type
correspondence between Sp(1)/SO(4) instanton partition functions and chiral
blocks with an underlying W(2,2)-algebra symmetry. This form of the
correspondence eliminates the need to divide out extra U(1) factors. Finally,
to check this correspondence for linear quivers, we compute expressions for the
Sp(1)-SO(4) half-bifundamental.Comment: 83 pages, 29 figures; minor change
A note on the peeling theorem in higher dimensions
We demonstrate the ``peeling property'' of the Weyl tensor in higher
dimensions in the case of even dimensions (and with some additional
assumptions), thereby providing a first step towards understanding of the
general peeling behaviour of the Weyl tensor, and the asymptotic structure at
null infinity, in higher dimensions.Comment: 5 pages, to appear in Class. Quantum Gra
Stability in Designer Gravity
We study the stability of designer gravity theories, in which one considers
gravity coupled to a tachyonic scalar with anti-de Sitter boundary conditions
defined by a smooth function W. We construct Hamiltonian generators of the
asymptotic symmetries using the covariant phase space method of Wald et al.and
find they differ from the spinor charges except when W=0. The positivity of the
spinor charge is used to establish a lower bound on the conserved energy of any
solution that satisfies boundary conditions for which has a global minimum.
A large class of designer gravity theories therefore have a stable ground
state, which the AdS/CFT correspondence indicates should be the lowest energy
soliton. We make progress towards proving this, by showing that minimum energy
solutions are static. The generalization of our results to designer gravity
theories in higher dimensions involving several tachyonic scalars is discussed.Comment: 29 page
Asymptotic structure of radiation in higher dimensions
We characterize a general gravitational field near conformal infinity (null,
spacelike, or timelike) in spacetimes of any dimension. This is based on an
explicit evaluation of the dependence of the radiative component of the Weyl
tensor on the null direction from which infinity is approached. The behaviour
similar to peeling property is recovered, and it is shown that the directional
structure of radiation has a universal character that is determined by the
algebraic type of the spacetime. This is a natural generalization of analogous
results obtained previously in the four-dimensional case.Comment: 14 pages, no figures (two references added
On the dynamics of a quadratic scalar field potential
We review the attractor properties of the simplest chaotic model of
inflation, in which a minimally coupled scalar field is endowed with a
quadratic scalar potential. The equations of motion in a flat
Friedmann-Robertson-Walker universe are written as an autonomous system of
equations, and the solutions of physical interest appear as critical points.
This new formalism is then applied to the study of inflation dynamics, in which
we can go beyond the known slow-roll formalism of inflation.Comment: 14 pages, 6 eps figures, matches version to appear in IJMP
Uniqueness and nonuniqueness of the stationary black holes in 5D Einstein-Maxwell and Einstein-Maxwell-dilaton gravity
In the present paper we investigate the general problem of uniqueness of the
stationary black solutions in 5D Einstein-Maxwell-dilaton gravity with
arbitrary dilaton coupling parameter containing the Einstein-Maxwell gravity as
a particular case. We formulate and prove uniqueness theorems classifying the
stationary black hole solutions in terms of their interval structure, electric
and magnetic charges and the magnetic fluxes. The proofs are based on the
nonpositivity of the Riemann curvature operator on the space of the potentials
which imposes restrictions on the dilaton coupling parameter.Comment: 21 pages, LaTe
Supersymmetric Field-Theoretic Models on a Supermanifold
We propose the extension of some structural aspects that have successfully
been applied in the development of the theory of quantum fields propagating on
a general spacetime manifold so as to include superfield models on a
supermanifold. We only deal with the limited class of supermanifolds which
admit the existence of a smooth body manifold structure. Our considerations are
based on the Catenacci-Reina-Teofillatto-Bryant approach to supermanifolds. In
particular, we show that the class of supermanifolds constructed by
Bonora-Pasti-Tonin satisfies the criterions which guarantee that a
supermanifold admits a Hausdorff body manifold. This construction is the
closest to the physicist's intuitive view of superspace as a manifold with some
anticommuting coordinates, where the odd sector is topologically trivial. The
paper also contains a new construction of superdistributions and useful results
on the wavefront set of such objects. Moreover, a generalization of the
spectral condition is formulated using the notion of the wavefront set of
superdistributions, which is equivalent to the requirement that all of the
component fields satisfy, on the body manifold, a microlocal spectral condition
proposed by Brunetti-Fredenhagen-K\"ohler.Comment: Final version to appear in J.Math.Phy
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