323 research outputs found
Aharonov-Bohm scattering of charged particles and neutral atoms: the role of absorption
The Aharonov-Bohm scattering of charged particles by the magnetic field of an
infinitely long and infinitely thin solenoid (magnetic string) in an absorbing
medium is studied. We discuss the partial-wave approach to this problem and
show that standard partial-wave method can be adjusted to this case. The effect
of absorption leads to oscillations of the AB cross section.
Based on this we investigate the scattering of neutral atoms with induced
electric dipole moments by a charge wire of finite radius which is placed in an
uniform magnetic field. The physical realistic and practically important case
that all atoms which collide with the wire are totally absorbed at its surface,
is studied in detail. The dominating terms of the scattering amplitude are
evaluated analytically for different physical constellations. The rest terms
are written in a form suitable for a numerical computation. We show that if the
magnetic field is absent, the absorbing charged wire causes oscillations of the
cross section. In the presence of the magnetic field the cross section
increases and the dominating Aharonov--Bohm peak appears in the forward
direction, suppressing the oscillations.Comment: 15 pages, LaTeXfile, 2 figure
A pragmatic approach to the problem of the self-adjoint extension of Hamilton operators with the Aharonov-Bohm potential
We consider the problem of self-adjoint extension of Hamilton operators for
charged quantum particles in the pure Aharonov-Bohm potential (infinitely thin
solenoid). We present a pragmatic approach to the problem based on the
orthogonalization of the radial solutions for different quantum numbers. Then
we discuss a model of a scalar particle with a magnetic moment which allows to
explain why the self-adjoint extension contains arbitrary parameters and give a
physical interpretation.Comment: 8 pages, LaTeX, to appear in J. Phys.
Perturbative Study of Bremsstrahlung and Pair-Production by Spin-1/2 Particles in the Aharonov-Bohm Potential
In the presence of an external Aharonov-Bohm potential, we investigate the
two QED processes of the emission of a bremsstrahlung photon by an electron,
and the production of an electron-positron pair by a single photon.
Calculations are carried out using the Born approximation within the framework
of covariant perturbation theory to lowest non-vanishing order in \alpha. The
matrix element for each process is derived, and the corresponding differential
cross-section is calculated. In the non-relativistic limit, the resulting
angular and spectral distributions and some polarization properties are
considered, and compared to results of previous works.Comment: 15 pages, RevTex 4, 2 figures, submitted for publicatio
Quantum Tests of the Foundations of General Relativity
The role of the equivalence principle in the context of non-relativistic
quantum mechanics and matter wave interferometry, especially atom beam
interferometry, will be discussed. A generalised form of the weak equivalence
principle which is capable of covering quantum phenomena too, will be proposed.
It is shown that this generalised equivalence principle is valid for matter
wave interferometry and for the dynamics of expectation values. In addition,
the use of this equivalence principle makes it possible to determine the
structure of the interaction of quantum systems with gravitational and inertial
fields. It is also shown that the path of the mean value of the position
operator in the case of gravitational interaction does fulfill this generalised
equivalence principle.Comment: Classical and Quantum Gravity 15, 13 (1998
Quantized Roentgen Effect in Bose-Einstein Condensates
A classical dielectric moving in a charged capacitor can create a magnetic
field (Roentgen effect). A quantum dielectric, however, will not produce a
magnetization, except at vortices. The magnetic field outside the quantum
dielectric appears as the field of quantized monopoles
Particle creation in a colliding plane wave spacetime: wave packet quantization
We use wave packet mode quantization to compute the creation of massless
scalar quantum particles in a colliding plane wave spacetime. The background
spacetime represents the collision of two gravitational shock waves followed by
trailing gravitational radiation which focus into a Killing-Cauchy horizon. The
use of wave packet modes simplifies the problem of mode propagation through the
different spacetime regions which was previously studied with the use of
monocromatic modes. It is found that the number of particles created in a given
wave packet mode has a thermal spectrum with a temperature which is inversely
proportional to the focusing time of the plane waves and which depends on the
mode trajectory.Comment: 23, latex, figures available by fa
On the physical meaning of Fermi coordinates
(Some Latex problems should be removed in this version) Fermi coordinates
(FC) are supposed to be the natural extension of Cartesian coordinates for an
arbitrary moving observer in curved space-time. Since their construction cannot
be done on the whole space and even not in the whole past of the observer we
examine which construction principles are responsible for this effect and how
they may be modified. One proposal for a modification is made and applied to
the observer with constant acceleration in the two and four dimensional
Minkowski space. The two dimensional case has some surprising similarities to
Kruskal space which generalize those found by Rindler for the outer region of
Kruskal space and the Rindler wedge. In perturbational approaches the
modification leads also to different predictions for certain physical systems.
As an example we consider atomic interferometry and derive the deviation of the
acceleration-induced phase shift from the standard result in Fermi coordinates.Comment: 11 pages, KONS-RGKU-94/02 (Latex
Scalar Pair Production in the Aharonov-Bohm Potential
In the framework of QED, scalar pair production by a single linearly
polarized high-energy photon in the presence of an external Aharonov-Bohm
potential is investigated. The exact scattering solutions of the Klein-Gordon
equation in cylindrically symmetric field are constructed and used to write the
first order transition amplitude. The matrix elements and the corresponding
differential scattering cross-section are calculated. The pair production at
both the nonrelativistic and the ultrarelativistic limits is discussed.Comment: 13 pages, 1 figur
Nothing Ventured — Nothing Gained? Empirical Evidence on Venture Capital Financing in Switzerland
- …