181,402 research outputs found
Diffraction and quasiclassical limit of the Aharonov--Bohm effect
Since the Aharonov-Bohm effect is the purely quantum effect that has no
analogues in classical physics, its persistence in the quasiclassical limit
seems to be hardly possible. Nevertheless, we show that the scattering
Aharonov-Bohm effect does persist in the quasiclassical limit owing to the
diffraction, i.e. the Fraunhofer diffraction in the case when space outside the
enclosed magnetic flux is Euclidean, and the Fresnel diffraction in the case
when the outer space is conical. Hence, the enclosed magnetic flux can serve as
a gate for the propagation of short-wavelength, almost classical, particles. In
the case of conical space, this quasiclassical effect which is in principle
detectable depends on the particle spin.Comment: 12 pages, minor changes, references update
Curvature Expansion for the Gluodynamics String including Perturbative Gluonic Contributions
Perturbation theory in the nonperturbative QCD vacuum and the non-Abelian
Stokes theorem, representing a Wilson loop in the SU(2) gluodynamics as an
integral over all the orientations in colour space, are applied to a derivation
of the correction to the string effective action in the lowest order in the
coupling constant . This correction is due to the interaction of
perturbative gluons with the string world sheet and affects only the coupling
constant of the rigidity term, while its contribution to the string tension of
the Nambu-Goto term vanishes. The obtained correction to the rigidity coupling
constant multiplicatively depends on the colour "spin" of the representation of
the Wilson loop under consideration and a certain path integral, which includes
the background Wilson loop average.Comment: 9 pages, LaTeX, no figure
Properties of tunnel Josephson junctions with a ferromagnetic interlayer
We investigate superconductor/insulator/ferromagnet/superconductor (SIFS)
tunnel Josephson junctions in the dirty limit, using the quasiclassical theory.
We formulate a quantitative model describing the oscillations of critical
current as a function of thickness of the ferromagnetic layer and use this
model to fit recent experimental data. We also calculate quantitatively the
density of states (DOS) in this type of junctions and compare DOS oscillations
with those of the critical current.Comment: 9 pages, 8 figures, to be published in Phys. Rev.
Contextual approach to quantum mechanics and the theory of the fundamental prespace
We constructed a Hilbert space representation of a contextual Kolmogorov
model. This representation is based on two fundamental observables -- in the
standard quantum model these are position and momentum observables. This
representation has all distinguishing features of the quantum model. Thus in
spite all ``No-Go'' theorems (e.g., von Neumann, Kochen and Specker,..., Bell)
we found the realist basis for quantum mechanics. Our representation is not
standard model with hidden variables. In particular, this is not a reduction of
quantum model to the classical one. Moreover, we see that such a reduction is
even in principle impossible. This impossibility is not a consequence of a
mathematical theorem but it follows from the physical structure of the model.
By our model quantum states are very rough images of domains in the space of
fundamental parameters - PRESPACE. Those domains represent complexes of
physical conditions. By our model both classical and quantum physics describe
REDUCTION of PRESPACE-INFORMATION. Quantum mechanics is not complete. In
particular, there are prespace contexts which can be represented only by a so
called hyperbolic quantum model. We predict violations of the Heisenberg's
uncertainty principle and existence of dispersion free states.Comment: Plenary talk at Conference "Quantum Theory: Reconsideration of
Foundations-2", Vaxjo, 1-6 June, 200
Vibrating the QCD string
The large distance behaviour of the adiabatic hybrid potentials is studied in
the framework of the QCD string model. The calculated spectra are shown to be
the result of interplay between potential-type longitudinal and string-type
transverse vibrations.Comment: LaTeX2e, 9 pages, 2 Postscript figures, final version to appear in
Yad.Fi
- …