11,317 research outputs found
An Intrinsic Approach to Forces in Magnetoelectric Media
This paper offers a conceptually straightforward method for the calculation
of stresses in polarisable media based on the notion of a drive form and its
property of being closed in spacetimes with symmetry. After an outline of the
notation required to exploit the powerful exterior calculus of differential
forms, a discussion of the relation between Killing isometries and conservation
laws for smooth and distributional drive forms is given. Instantaneous forces
on isolated spacetime domains and regions with interfaces are defined, based on
manifestly covariant equations of motion. The remaining sections apply these
notions to media that sustain electromagnetic stresses, with emphasis on
homogeneous magnetoelectric material. An explicit calculation of the average
pressure exerted by a monochromatic wave normally incident on a homogeneous,
magnetoelectric slab in vacuo is presented and the concluding section
summarizes how this pressure depends on the parameters in the magnetoelectric
tensors for the medium.Comment: 25 pages, 3 figures, to appear in Il Nuovo Cimento B, proceedings of
GCM8, Catania (Oct 2008) - References added, minor corrections mad
Solutions for Neutral for Axi-Dilaton Gravity in 4-Dimensions
We examine a 1 parameter class of actions describing the gravitational
interaction between a pair of scalar fields and Einsteinian gravitation. When
the parameter is positive the theory corresponds to an axi-dilatonic sector of
low energy string theory. We exploit an SL(2,R) symmetry of the theory to
construct a family of electromagnetically neutral solutions with non-zero axion
and dilaton charge from solutions of the Brans-Dicke theory. We also comment on
solutions to the theory with negative coupling parameter.Comment: 7 pages Plain Tex (No Figures), Letter to Editor, Classical and
Quantum Gravit
Mobile radio alternative systems study. Volume 1: Traffic model
The markets for mobile radio services in non-urban areas of the United States are examined for the years 1985-2000. Three market categories are identified. New Services are defined as those for which there are different expressed ideas but which are not now met by any application of available technology. The complete fulfillment of the needs requires nationwide radio access to vehicles without knowledge of vehicle location, wideband data transmission from remote sites, one- and two way exchange of short data and control messages between vehicles and dispatch or control centers, and automatic vehicle location (surveillance). The commercial and public services market of interest to the study is drawn from existing users of mobile radio in non-urban areas who are dissatisfied with the geographical range or coverage of their systems. The mobile radio telephone market comprises potential users who require access to the public switched telephone network in areas that are not likely to be served by the traditional growth patterns of terrestrial mobile telephone services. Conservative, likely, and optimistic estimates of the markets are presented in terms of numbers of vehicles that will be served and the radio traffic they will generate
<Contributed Talk 42>Validated numerics and Hilbert's 16th problem
[Date] November 28 (Mon) - December 2 (Fri), 2011: [Place] Kyoto University Clock Tower Centennial Hall, Kyoto, JAPA
Non-Riemannian Gravity and the Einstein-Proca System
We argue that all Einstein-Maxwell or Einstein-Proca solutions to general
relativity may be used to construct a large class of solutions (involving
torsion and non-metricity) to theories of non-Riemannian gravitation that have
been recently discussed in the literature.Comment: 9 pages Plain Tex (No Figures), Letter to Editor Classical and
Quantum Gravit
A Broken Gauge Approach to Gravitational Mass and Charge
We argue that a spontaneous breakdown of local Weyl invariance offers a mechanism in which gravitational interactions contribute to the generation of particle masses and their electric charge. The theory is formulated in terms of a spacetime geometry whose natural connection has both dynamic torsion and non-metricity. Its structure illuminates the role of dynamic scales used to determine measurable aspects of particle interactions and it predicts an additional neutral vector boson with electroweak properties
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