5,324 research outputs found
Ion-tracer anemometer
Gas velocity measuring instrument measures transport time of ion-trace traveling fixed distance between ionization probe and detector probe. Electric field superimposes drift velocity onto flow velocity so travel times can be reduced to minimize ion diffusion effects
Coulomb field of an accelerated charge: physical and mathematical aspects
The Maxwell field equations relative to a uniformly accelerated frame, and
the variational principle from which they are obtained, are formulated in terms
of the technique of geometrical gauge invariant potentials. They refer to the
transverse magnetic (TM) and the transeverse electric (TE) modes. This gauge
invariant "2+2" decomposition is used to see how the Coulomb field of a charge,
static in an accelerated frame, has properties that suggest features of
electromagnetism which are different from those in an inertial frame. In
particular, (1) an illustrative calculation shows that the Larmor radiation
reaction equals the electrostatic attraction between the accelerated charge and
the charge induced on the surface whose history is the event horizon, and (2) a
spectral decomposition of the Coulomb potential in the accelerated frame
suggests the possibility that the distortive effects of this charge on the
Rindler vacuum are akin to those of a charge on a crystal lattice.Comment: 27 pages, PlainTex. Related papers available at
http://www.math.ohio-state.edu/~gerlac
On the exciton binding energy in a quantum well
We consider a model describing the one-dimensional confinement of an exciton
in a symmetrical, rectangular quantum-well structure and derive upper and lower
bounds for the binding energy of the exciton. Based on these bounds, we
study the dependence of on the width of the confining potential with a
higher accuracy than previous reports. For an infinitely deep potential the
binding energy varies as expected from at large widths to at
small widths. For a finite potential, but without consideration of a mass
mismatch or a dielectric mismatch, we substantiate earlier results that the
binding energy approaches the value for both small and large widths,
having a characteristic peak for some intermediate size of the slab. Taking the
mismatch into account, this result will in general no longer be true. For the
specific case of a quantum-well
structure, however, and in contrast to previous findings, the peak structure is
shown to survive.Comment: 32 pages, ReVTeX, including 9 figure
What is the Geometry of Superspace ?
We investigate certain properties of the Wheeler-DeWitt metric (for constant
lapse) in canonical General Relativity associated with its non-definite nature.
Contribution to the conference on Mach's principle: "From Newtons Bucket to
Quantum Gravity", July 26-30 1993, Tuebingen, GermanyComment: 10 pages, Plain Te
The generalization of the Regge-Wheeler equation for self-gravitating matter fields
It is shown that the dynamical evolution of perturbations on a static
spacetime is governed by a standard pulsation equation for the extrinsic
curvature tensor. The centerpiece of the pulsation equation is a wave operator
whose spatial part is manifestly self-adjoint. In contrast to metric
formulations, the curvature-based approach to gravitational perturbation theory
generalizes in a natural way to self-gravitating matter fields. For a certain
relevant subspace of perturbations the pulsation operator is symmetric with
respect to a positive inner product and therefore allows spectral theory to be
applied. In particular, this is the case for odd-parity perturbations of
spherically symmetric background configurations. As an example, the pulsation
equations for self-gravitating, non-Abelian gauge fields are explicitly shown
to be symmetric in the gravitational, the Yang Mills, and the off-diagonal
sector.Comment: 4 pages, revtex, no figure
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