2,235 research outputs found
On the gravitational field of static and stationary axial symmetric bodies with multi-polar structure
We give a physical interpretation to the multi-polar Erez-Rozen-Quevedo
solution of the Einstein Equations in terms of bars. We find that each
multi-pole correspond to the Newtonian potential of a bar with linear density
proportional to a Legendre Polynomial. We use this fact to find an integral
representation of the function. These integral representations are
used in the context of the inverse scattering method to find solutions
associated to one or more rotating bodies each one with their own multi-polar
structure.Comment: To be published in Classical and Quantum Gravit
Third order superintegrable systems separating in polar coordinates
A complete classification is presented of quantum and classical
superintegrable systems in that allow the separation of variables in
polar coordinates and admit an additional integral of motion of order three in
the momentum. New quantum superintegrable systems are discovered for which the
potential is expressed in terms of the sixth Painlev\'e transcendent or in
terms of the Weierstrass elliptic function
Psi-Series Solution of Fractional Ginzburg-Landau Equation
One-dimensional Ginzburg-Landau equations with derivatives of noninteger
order are considered. Using psi-series with fractional powers, the solution of
the fractional Ginzburg-Landau (FGL) equation is derived. The leading-order
behaviours of solutions about an arbitrary singularity, as well as their
resonance structures, have been obtained. It was proved that fractional
equations of order with polynomial nonlinearity of order have the
noninteger power-like behavior of order near the singularity.Comment: LaTeX, 19 pages, 2 figure
Hamiltonians separable in cartesian coordinates and third-order integrals of motion
We present in this article all Hamiltonian systems in E(2) that are separable
in cartesian coordinates and that admit a third-order integral, both in quantum
and in classical mechanics. Many of these superintegrable systems are new, and
it is seen that there exists a relation between quantum superintegrable
potentials, invariant solutions of the Korteweg-De Vries equation and the
Painlev\'e transcendents.Comment: 19 pages, Will be published in J. Math. Phy
General-relativistic Model of Magnetically Driven Jet
The general scheme for the construction of the general-relativistic model of
the magnetically driven jet is suggested. The method is based on the usage of
the 3+1 MHD formalism. It is shown that the critical points of the flow and the
explicit radial behavior of the physical variables may be derived through the
jet ``profile function."Comment: 12 pages, LaTex, no figure
Conceptual framework for scenarios development in the Water futures and Solutions project
The major purpose of the Water Futures & Solutions (WFaS) initiative is to develop a set of adaptable resilient and robust solutions and a framework to facilitate access to and guidance through them by decision makers facing a variety of water-related challenges to sustainable evelopment, and a set of optional pathways to achieve plausible sustainable development goals by 2050.
The WFaS Initiative addresses the multidimensional aspects of the water system and is guided by stakeholders representing these various aspects. The Initiative views freshwater systems as being strongly interweaved with human activities (Economy, Society) and Nature as a whole. Dynamics and health of freshwater systems is critical to human well- being. The Initiative will go beyond scenario production and model comparisons and will focus on exploring solutions and necessary innovations to address the growing water challenges. Solutions can be combinations of technological innovations, regulatory approaches, manageent or institutional changes that improve the balance of water supply and demand, improve water quality, or reduce water-related risks for society. Solutions will often be embedded in and cut across all sectors of social and economic activities. In order to represent the aspirations and interdependencies as described above, the conceptual framework has been developed, to communicate project results to the target audiences.
This document describes this conceptual framework that will be used:
-to support development of qualitative water scenarios -to identify and select critical dimensions of the water scenarios -to guide integration of scenarios with quantitative models -to guide integration of information from various data sources into the scenarios -to support development and assessment of solutions -to support collaboration between project and stakeholder groups -to facilitate presentation of results to target audiences
The WFaS conceptual framework is developed using the 'concept maps' technique (Caqas and Carff, 2005; Novak and Caqas, 2006b). Concept maps method was develop to represent knowledge in an organized way. It allows practitioners to represent concepts and specific relationships between concepts. It is flexible enough to adapt to different knowledge domains to support better understanding and communication between individuals and groups from different backgrounds
Canonical Quantization of the Gowdy Model
The family of Gowdy universes with the spatial topology of a three-torus is
studied both classically and quantum mechanically. Starting with the Ashtekar
formulation of Lorentzian general relativity, we introduce a gauge fixing
procedure to remove almost all of the non-physical degrees of freedom. In this
way, we arrive at a reduced model that is subject only to one homogeneous
constraint. The phase space of this model is described by means of a canonical
set of elementary variables. These are two real, homogeneous variables and the
Fourier coefficients for four real fields that are periodic in the angular
coordinate which does not correspond to a Killing field of the Gowdy
spacetimes. We also obtain the explicit expressions for the line element and
reduced Hamiltonian. We then proceed to quantize the system by representing the
elementary variables as linear operators acting on a vector space of analytic
functionals. The inner product on that space is selected by imposing Lorentzian
reality conditions. We find the quantum states annihilated by the operator that
represents the homogeneous constraint of the model and construct with them the
Hilbert space of physical states. Finally, we derive the general form of the
quantum observables of the model.Comment: 13 pages, Revte
Geroch--Kinnersley--Chitre group for Dilaton--Axion Gravity
Kinnersley--type representation is constructed for the four--dimensional
Einstein--Maxwell--dilaton--axion system restricted to space--times possessing
two non--null commuting Killing symmetries. New representation essentially uses
the matrix--valued formulation and effectively reduces the
construction of the Geroch group to the corresponding problem for the vacuum
Einstein equations. An infinite hierarchy of potentials is introduced in terms
of real symmetric matrices generalizing the scalar hierarchy of
Kinnersley--Chitre known for the vacuum Einstein equations.Comment: Published in ``Quantum Field Theory under the Influence of External
Conditions'', M. Bordag (Ed.) (Proc. of the International Workshop, Leipzig,
Germany, 18--22 September 1995), B.G. Teubner Verlagsgessellschaft,
Stuttgart--Leipzig, 1996, pp. 228-23
A pilot trial to evaluate the acute toxicity and feasibility of tamoxifen for prevention of breast cancer.
Epidemiological and experimental evidence indicates that oestrogens are involved in the carcinogenic promotion of human breast cancer. We have undertaken a pilot trial of tamoxifen, an anti-oestrogen, compared to placebo given to 200 women at a high risk of developing breast cancer. The results of this trial show that acute toxicity is low and that accrual and compliance are satisfactory. Furthermore, biochemical monitoring of lipids and clotting factors indicate that tamoxifen may reduce the risk of cardiovascular deaths. At this stage no untoward long-term risks have been identified, and it is therefore proposed that a large multicentre trial should be started
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