5,934 research outputs found
Reciprocal relativity of noninertial frames and the quaplectic group
Newtonian mechanics has the concept of an absolute inertial rest frame.
Special relativity eliminates the absolute rest frame but continues to require
the absolute inertial frame. General relativity solves this for gravity by
requiring particles to have locally inertial frames on a curved position-time
manifold. The problem of the absolute inertial frame for other forces remains.
We look again at the transformations of frames on an extended phase space with
position, time, energy and momentum degrees of freedom. Under nonrelativistic
assumptions, there is an invariant symplectic metric and a line element dt^2.
Under special relativistic assumptions the symplectic metric continues to be
invariant but the line elements are now -dt^2+dq^2/c^2 and dp^2-de^2/c^2. Max
Born conjectured that the line element should be generalized to the pseudo-
orthogonal metric -dt^2+dq^2/c^2+ (1/b^2)(dp^2-de^2/c^2). The group leaving
these two metrics invariant is the pseudo-unitary group of transformations
between noninertial frames. We show that these transformations eliminate the
need for an absolute inertial frame by making forces relative and bounded by b
and so embodies a relativity that is 'reciprocal' in the sense of Born. The
inhomogeneous version of this group is naturally the semidirect product of the
pseudo-unitary group with the nonabelian Heisenberg group. This is the
quaplectic group. The Heisenberg group itself is the semidirect product of two
translation groups. This provides the noncommutative properties of position and
momentum and also time and energy that are required for the quantum mechanics
that results from considering the unitary representations of the quaplectic
group.Comment: Substantial revision, Publicon LaTe
Singularity-Free Electrodynamics for Point Charges and Dipoles: Classical Model for Electron Self-Energy and Spin
It is shown how point charges and point dipoles with finite self-energies can
be accomodated into classical electrodynamics. The key idea is the introduction
of constitutive relations for the electromagnetic vacuum, which actually
mirrors the physical reality of vacuum polarization. Our results reduce to
conventional electrodynamics for scales large compared to the classical
electron radius cm. A classical simulation for a
structureless electron is proposed, with the appropriate values of mass, spin
and magnetic moment.Comment: 3 page
Vacuum field correlations and three-body Casimir-Polder potential with one excited atom
The three-body Casimir-Polder potential between one excited and two
ground-state atoms is evaluated. A physical model based on the dressed field
correlations of vacuum fluctuations is used, generalizing a model previously
introduced for three ground-state atoms. Although the three-body potential with
one excited atom is already known in the literature, our model gives new
insights on the nature of non-additive Casimir-Polder forces with one or more
excited atoms.Comment: 9 page
Development of a simulation-based decision support tool for renewable energy integration and demand-supply matching
This paper describes a simulation-based decision support tool, MERIT, which has been developed to assist in the assessment of renewable energy systems by focusing on the degree of match achievable between energy demand and supply. Models are described for the prediction of the performance of PV, wind and battery technologies. These models are based on manufacturers' specifications, location-related parameters and hourly weather data. The means of appraising the quality of match is outlined and examples are given of the application of the tool at the individual building and community levels
Development and demonstration of a renewable energy based demand/supply decision support tool for the building design profession
Future cities are likely to be characterised by a greater level of renewable energy systems deployment. Maximum impact will be achieved when such systems are used to offset local energy demands in contrast to current philosophy dictating the grid connection of large schemes. This paper reports on the development of a software tool, MERIT, for demand/ supply matching. The purpose of MERIT is to assist with the deployment of renewable energy systems at all scales. This paper describes the procedures used to match heterogeneous supply technologies to a set of demand profiles corresponding to the different possible fuel types
A liquid crystal analogue of the cosmic string
We consider the propagation of light in a anisotropic medium with a
topological line defect in the realm of geometrical optics. It is shown that
the effective geometry perceived by light propagating in such medium is that of
a spacial section of the cosmic string spacetime.Comment: 3 pages, 2 figures. Modern Physics Letters A, accepted for
publicatio
Evolving wormhole geometries within nonlinear electrodynamics
In this work, we explore the possibility of evolving (2+1) and
(3+1)-dimensional wormhole spacetimes, conformally related to the respective
static geometries, within the context of nonlinear electrodynamics. For the
(3+1)-dimensional spacetime, it is found that the Einstein field equation
imposes a contracting wormhole solution and the obedience of the weak energy
condition. Nevertheless, in the presence of an electric field, the latter
presents a singularity at the throat, however, for a pure magnetic field the
solution is regular. For the (2+1)-dimensional case, it is also found that the
physical fields are singular at the throat. Thus, taking into account the
principle of finiteness, which states that a satisfactory theory should avoid
physical quantities becoming infinite, one may rule out evolving
(3+1)-dimensional wormhole solutions, in the presence of an electric field, and
the (2+1)-dimensional case coupled to nonlinear electrodynamics.Comment: 17 pages, 1 figure; to appear in Classical and Quantum Gravity. V2:
minor corrections, including a referenc
Localized low-frequency Neumann modes in 2d-systems with rough boundaries
We compute the relative localization volumes of the vibrational eigenmodes in
two-dimensional systems with a regular body but irregular boundaries under
Dirichlet and under Neumann boundary conditions. We find that localized states
are rare under Dirichlet boundary conditions but very common in the Neumann
case. In order to explain this difference, we utilize the fact that under
Neumann conditions the integral of the amplitudes, carried out over the whole
system area is zero. We discuss, how this condition leads to many localized
states in the low-frequency regime and show by numerical simulations, how the
number of the localized states and their localization volumes vary with the
boundary roughness.Comment: 7 pages, 4 figure
Transient behavior of surface plasmon polaritons scattered at a subwavelength groove
We present a numerical study and analytical model of the optical near-field
diffracted in the vicinity of subwavelength grooves milled in silver surfaces.
The Green's tensor approach permits computation of the phase and amplitude
dependence of the diffracted wave as a function of the groove geometry. It is
shown that the field diffracted along the interface by the groove is equivalent
to replacing the groove by an oscillating dipolar line source. An analytic
expression is derived from the Green's function formalism, that reproduces well
the asymptotic surface plasmon polariton (SPP) wave as well as the transient
surface wave in the near-zone close to the groove. The agreement between this
model and the full simulation is very good, showing that the transient
"near-zone" regime does not depend on the precise shape of the groove. Finally,
it is shown that a composite diffractive evanescent wave model that includes
the asymptotic SPP can describe the wavelength evolution in this transient
near-zone. Such a semi-analytical model may be useful for the design and
optimization of more elaborate photonic circuits whose behavior in large part
will be controlled by surface waves.Comment: 12 pages, 10 figure
Vertical cavity surface emitting laser action of an all monolithic ZnO-based microcavity
We report on room temperature laser action of an all monolithic ZnO-based
vertical cavity surface emitting laser (VCSEL) under optical pumping. The VCSEL
structure consists of a 2{\lambda} microcavity containing 8
ZnO/Zn(0.92)Mg(0.08)O quantum wells embedded in epitaxially grown
Zn(0.92)Mg(0.08)O/Zn(0.65)Mg(0.35)O distributed Bragg reflectors (DBRs). As a
prerequisite, design and growth of high reflectivity DBRs based on ZnO and
(Zn,Mg)O for optical devices operating in the ultraviolet and blue-green
spectral range are discussed.Comment: Copyright (2011) American Institute of Physics. This article may be
downloaded for personal use only. Any other use requires prior permission of
the author and the American Institute of Physics. The following article
appeared in Appl. Phys. Lett. 98, 011101 (2011) and may be found at
http://apl.aip.org/resource/1/applab/v98/i1/p011101_s
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