161.
Virtual photons in imaginary time: Computing exact Casimir forces via
standard numerical-electromagnetism techniques - Rodriguez, Alejandro; Ibanescu, Mihai; Iannuzzi, Davide; Joannopoulos, J. D.; Johnson, Steven G.
We describe a numerical method to compute Casimir forces in arbitrary
geometries, for arbitrary dielectric and metallic materials, with arbitrary
accuracy (given sufficient computational resources). Our approach, based on
well established integration of the mean stress tensor evaluated via the
fluctuation dissipation theorem, is designed to directly exploit fast methods
developed for classical computational electromagnetism, since it only involves
repeated evaluation of the Greens function for imaginary frequencies
(equivalently, real frequencies in imaginary time). We develop the approach by
systematically examining various formulations of Casimir forces from the
previous decades and evaluating them according to their suitability for
numerical computation. We illustrate our approach with a simple
finite-difference frequency domain implementation,...
162.
On the Hamiltonian Approach and Path Integration for a Point Particle
Minimally Coupled to Electromagnetism - Skenderis, K.; van Nieuwenhuizen, P.
We {\em derive} the exact configuration space path integral, together with
the way how to evaluate it, from the Hamiltonian approach for any quantum
mechanical system in flat spacetime whose Hamiltonian has at most two momentum
operators. Starting from a given, covariant or non-covariant, Hamiltonian, we
go from the time-discretized path integral to the continuum path integral by
introducing Fourier modes. We prove that the limit $N \rightarrow \infty$ for
the terms in the perturbation expansion (``Feynman graphs'') exists, by
demonstrating that the series involved are uniformly convergent. {\em All}
terms in the expansion of the exponent in $$ contribute to...
163.
Clifford Valued Differential Forms, Algebraic Spinor Fields,
Gravitation, Electromagnetism and "Unified" Theories - de Oliveira, E. Capelas; Rodrigues Jr, W. A.
In this paper we show how to describe the general theory of a linear metric
compatible connection with the theory of Clifford valued differential forms.
This is done by realizing that for each spacetime point the algebra of Clifford
bivectors is isomorphic to the Lie algebra of Sl(2,C). In that way the pullback
of the linear connection under a trivialization of the bundle is represented by
a Clifford valued 1-form. That observation makes it possible to realize
Einstein's gravitational theory can be formulated in a way which is similar to
a Sl(2,C) gauge theory. Some aspects of such approach is discussed. Also, the
theory of the covariant spinor...
164.
Clifford Valued Differential Forms, and Some Issues in Gravitation,
Electromagnetism and 'Unified' Theories - Rodrigues Jr., Waldyr A.; de Oliveira, Edmundo Capelas
In this paper we show how to describe the general theory of a linear metric
compatible connection with the theory of Clifford valued differential forms.
This is done by realizing that for each spacetime point the Lie algebra of
Clifford bivectors is isomorphic to the Lie algebra of Sl(2,C). In that way the
pullback of the linear connection under a local trivialization of the bundle
(i.e., a choice of gauge) is represented by a Clifford valued 1-form. That
observation makes it possible to realize immediately that Einstein's
gravitational theory can be formulated in a way which is similar to a Sl(2,C)
gauge theory. Such a theory is compared...
165.
Effective Electric and Magnetic Local Actions for Electromagnetism with
two Gauge Fields - Ferreira, P. Castelo
A simple mechanism of dynamical symmetry breaking of electromagnetism with
two gauge fields ($U(1)\times U(1)$) is considered. By considering the action
variations with respect to the gauge connections $F=dA$ and $G=dC$ we obtain
that the extra gauge field $C$(or $A$) effectively is fixed by the
\textit{physical effective} field $A$(or $C$) constituting a non-trivial
configuration $C=C(A)$ (or $A=A(C)$) such that the field discontinuities (Dirac
string or Wu-Yang non-trivial fiber-bundle) are encoded in the extra gauge
field $C$ (or $A$). In this way we obtain an electric and a magnetic effective
actions (U(1)) that have an extra coupling to the magnetic and electric
currents (respectively) that decouple from the classical field...
166.
Diploma Project/Diplomarbeit (Mathematics/Computational Science & Engineering) Supervisor: Prof. Dr. R. Hiptmair (SAM, D-MATH) Impedance Boundary Conditions in Time Domain - Field Coputational Electromagnetism
convolution, absorbing boundary conditions, software development Problem. Alternating electromagnetic fields decay exponentially when penetrating a good conductor (skin effect). Therefore, a reasonable approximation of the electromagnetic Dirichlet-to-Neumann map of the interior of a good conductor is provided by the impedance boundary conditions Et = 1 √ µ 2(1 − i) (H × n) , (1) 2 σω where ω> 0 is a fixed angular frequency, characterizing the temporal variation of all electromagnetic fields. The conductivity σ and permeability µ are known material parameters. Issues. The relationship (1) is valid in the frequency domain only. However, often sinusoidal temporal variation of...
167.
Period of work Coaches - Electromagnetism Division; Marcel Van Roosmalen
analysis of the quality factor of etched rectangular, circular and ring resonators
168.
Evolução histórica da abordagem do electromagnetismo e indução electromagnética nos livros de texto para o ensino secundário - Saraiva, Carlos Alberto Alexandre
The importance of the textbook has been quite significant in the teaching/learning process. Throughout time it has been a privileged teaching instrument that has influenced the activities developed in the classroom. Some studies have stated that the school manual is one of the most used instruments by teachers.
The analysis of the contents has been chosen as a research object in the didactics of sciences with different objectives. Accounting for the role of the textbook, its analysis allows us to understand the way in which the electromagnetism and electromagnetic induction were introduced in the high school teaching and it can give...
169.
Les structures fines de l'\'{e}lectromagn\'{e}tisme classique et de la
relativit\'{e} restreinte (The fine structures of Classical Electromagnetism
and Special Relativity) - Pierseaux, Yves; Rousseaux, Germain
One of us (Y.P.) has shown the existence of a longitudinal component in the
propagation of light waves on the basis of the kinematics underlying
Poincar\'{e}'s ellipse. We show how this statement agrees with the
electromagnetic theory. We recall that the second of us supports the existence
of a "fine structure" of Electromagnetism that is, the co-existence of two
theories, one based on the fields (Heaviside-Hertz) and the other on the
potentials (Riemann-Lorenz). The existence of two different kinematics (the
"fine structure" of Special Relativity : Einstein or Poincar\'{e}) corresponds
to these two formulations of Classical Electromagnetism. With this goal in
mind, we prove the relativistic covariance of the...
170.
Plataforma docente de levitación magnética controlada por un PLC programable a través de Internet - Núñez Moreno, Fco Javier
En los últimos años la educación a distancia ha cobrado una gran importancia dentro delpanorama docente. Muchos son los motivos que han favorecido el desarrollo de este tipode educación, pero sin duda, el desarrollo de la tecnología de control y automatización hatenido una importancia relevante. Gracias a esta tecnología, se pueden crear laboratoriosremotos, facilitando de este modo el acceso de los estudiantes a material práctico.El siguiente proyecto consiste en la elaboración de un laboratorio remoto, basado en unelectroimán mediante el cual se tendrá control sobre un accionamiento a través deInternet. De esta forma, se permite a los estudiantes la posibilidad...
172.
Explicit Actions for Electromagnetism with Two Gauge Fields with Only
one Electric and one Magnetic Physical Fields - Ferreira, P. Castelo
We extend the work of Mello et al. based in Cabbibo and Ferrari concerning
the description of electromagnetism with two gauge fields from a variational
principle, i.e. an action. We provide a systematic independent derivation of
the allowed actions which have only one magnetic and one electric physical
fields and are invariant under the discrete symmetries $P$ and $T$. We conclude
that neither the Lagrangian, nor the Hamiltonian, are invariant under the
electromagnetic duality rotations. This agrees with the weak-strong coupling
mixing characteristic of the duality due to the Dirac quantization condition
providing a natural way to differentiate dual theories related by the duality
rotations (the energy is not...
173.
Electromagnetism and Gravitation - Dalton, Kenneth
The classical concept of "mass density" is not fundamental to the quantum
theory of matter. Therefore, mass density cannot be the source of gravitation.
Here, we treat electromagnetic energy, momentum, and stress as its source. The
resulting theory predicts that the gravitational potential near any charged
elementary particle is many orders of magnitude greater than the Newtonian
value.
174.
Gravitation and Electromagnetism II - Sidharth, B. G.
We show how, a non commutative underpinning for spacetime throws up mass,
spin and charge and indicate how it is possible to include QCD effects also.
175.
Electromagnetism and gravitation - Teller, Edward
Generation of electric fields in rapidly rotating insulators is discussed and calculated. An interesting effect is expected in TlCl. A possible appearance of magnetic fields near rapidly rotating gravitating bodies is proposed. The simple suggestion made here would lead to magnetic fields of negligible magnitude.
180.
Electromagnetism and gravitation - Teller, Edward
Generation of electric fields in rapidly rotating insulators is discussed and calculated. An interesting effect is expected in TlCl. A possible appearance of magnetic fields near rapidly rotating gravitating bodies is proposed. The simple suggestion made here would lead to magnetic fields of negligible magnitude.
161.
