2,110 research outputs found
Alternative derivation of the Feigel effect and call for its experimental verification
A recent theory by Feigel [Phys. Rev. Lett. {\bf 92}, 020404 (2004)] predicts
the finite transfer of momentum from the quantum vacuum to a fluid placed in
strong perpendicular electric and magnetic fields. The momentum transfer arises
because of the optically anisotropic magnetoelectric response induced in the
fluid by the fields. After summarising Feigel's original assumptions and
derivation (corrected of trivial mistakes), we rederive the same result by a
simpler route, validating Feigel's semi-classical approach. We then derive the
stress exerted by the vacuum on the fluid which, if the Feigel hypothesis is
correct, should induce a Poiseuille flow in a tube with maximum speed m/s (2000 times larger than Feigel's original prediction). An experiment
is suggested to test this prediction for an organometallic fluid in a tube
passing through the bore of a high strength magnet. The predicted flow can be
measured directly by tracking microscopy or indirectly by measuring the flow
rate (ml/min) corresponding to the Poiseuille flow. A second
experiment is also proposed whereby a `vacuum radiometer' is used to test a
recent prediction that the net force on a magnetoelectric slab in the vacuum
should be zero.Comment: 20 pages, 1 figures. revised and improved versio
Quantum radiation in a plane cavity with moving mirrors
We consider the electromagnetic vacuum field inside a perfect plane cavity
with moving mirrors, in the nonrelativistic approximation. We show that low
frequency photons are generated in pairs that satisfy simple properties
associated to the plane geometry. We calculate the photon generation rates for
each polarization as functions of the mechanical frequency by two independent
methods: on one hand from the analysis of the boundary conditions for moving
mirrors and with the aid of Green functions; and on the other hand by an
effective Hamiltonian approach. The angular and frequency spectra are discrete,
and emission rates for each allowed angular direction are obtained. We discuss
the dependence of the generation rates on the cavity length and show that the
effect is enhanced for short cavity lengths. We also compute the dissipative
force on the moving mirrors and show that it is related to the total radiated
energy as predicted by energy conservation.Comment: 17 pages, 1 figure, published in Physical Review
Schwinger, Pegg and Barnett and a relationship between angular and Cartesian quantum descriptions
From a development of an original idea due to Schwinger, it is shown that it
is possible to recover, from the quantum description of a degree of freedom
characterized by a finite number of states (\QTR{it}{i.e}., without classical
counterpart) the usual canonical variables of position/momentum \QTR{it}{and}
angle/angular momentum, relating, maybe surprisingly, the first as a limit of
the later.Comment: 7 pages, revised version, to appear on J. Phys. A: Math and Ge
Quantum radiation in external background fields
A canonical formalism is presented which allows for investigations of quantum
radiation induced by localized, smooth disturbances of classical background
fields by means of a perturbation theory approach. For massless,
non-selfinteracting quantum fields at zero temperature we demonstrate that the
low-energy part of the spectrum of created particles exhibits a non-thermal
character. Applied to QED in varying dielectrics the response theory approach
facilitates to study two distinct processes contributing to the production of
photons: the squeezing effect due to space-time varying properties of the
medium and of the velocity effect due to its motion. The generalization of this
approach to finite temperatures as well as the relation to sonoluminescence is
indicated.Comment: 20 page
One Loop Vaccum Polarization in a Locally de Sitter Background
We compute the one loop vacuum polarization from massless, minimally coupled
scalar QED in a locally de Sitter background. Gauge invariance is maintained
through the use of dimensional regularization, whereas conformal invariance is
explicitly broken by the scalar kinetic term as well as through the conformal
anomaly. A fully renormalized result is obtained. The one loop corrections to
the linearized, effective field equations do not vanish when evaluated
on-shell. In fact the on-shell one loop correction depends quadratically on the
inflationary scale factor, similar to a photon mass. The contribution from the
conformal anomaly is insignificant by comparison.Comment: 31 pages, LaTeX 2 epsilon, 4 figure
Vacuum polarization induced by a uniformly accelerated charge
We consider a point charge fixed in the Rindler coordinates which describe a
uniformly accelerated frame. We determine an integral expression of the induced
charge density due to the vacuum polarization at the first order in the fine
structure constant. In the case where the acceleration is weak, we give
explicitly the induced electrostatic potential.Comment: 13 pages, latex, no figures, to appear in Int. J. Theor. Phys
Quaternion Gravi-Electromagnetism
Defining the generalized charge, potential, current and generalized fields as
complex quantities where real and imaginary parts represent gravitation and
electromagnetism respectively, corresponding field equation, equation of motion
and other quantum equations are derived in manifestly covariant manner. It has
been shown that the field equations are invariant under Lorentz as well as
duality transformations. It has been shown that the quaternionic formulation
presented here remains invariant under quaternion transformations.Comment: Key Words: Quaternion, dyons, gravito-dyons, gravi-electromagnetism.
PACS No.: 04.90. +e ; 14.80. H
The Schwinger Nonet Mass and Sakurai Mass-Mixing Angle Formulae Reexamined
We study the origins of the inaccuracies of Schwinger's nonet mass, and the
Sakurai mass-mixing angle, formulae for the pseudoscalar meson nonet, and
suggest new versions of them, modified by the inclusion of the pseudoscalar
decay constants. We use these new formulae to determine the pseudoscalar decay
constants and mixing angle. The results obtained, f_8/f_\pi =1.185\pm 0.040,
f_9/f_\pi =1.095\pm 0.020, f_\eta /f_\pi =1.085\pm 0.025, f_{\eta ^{'}}/f_\pi
=1.195\pm 0.035, \theta =(-21.4\pm 1.0)^o, are in excellent agreement with
experiment.Comment: 17 pages, LaTe
The Logic behind Feynman's Paths
The classical notions of continuity and mechanical causality are left in
order to refor- mulate the Quantum Theory starting from two principles: I) the
intrinsic randomness of quantum process at microphysical level, II) the
projective representations of sym- metries of the system. The second principle
determines the geometry and then a new logic for describing the history of
events (Feynman's paths) that modifies the rules of classical probabilistic
calculus. The notion of classical trajectory is replaced by a history of
spontaneous, random an discontinuous events. So the theory is reduced to
determin- ing the probability distribution for such histories according with
the symmetries of the system. The representation of the logic in terms of
amplitudes leads to Feynman rules and, alternatively, its representation in
terms of projectors results in the Schwinger trace formula.Comment: 15 pages, contribution to Mario Castagnino Festschrif
Squeezing and photon distribution in a vibrating cavity
We obtain explicit analytical expressions for the quadrature variances and
the photon distribution functions of the electromagnetic field modes excited
from vacuum or thermal states due to the non-stationary Casimir effect in an
ideal one-dimensional Fabry--Perot cavity with vibrating walls, provided the
frequency of vibrations is close to a multiple frequency of the fundamental
unperturbed electromagnetic mode.Comment: 20 pages, LaTex2e, iopart document class, 2 ps figures, accepted for
publication in J. Phys.
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