8,095 research outputs found
Dynamics of Fluxon Lattice in Two Coupled Josephson Junctions
We study theoretically the dynamics of a fluxon Lattice (FL) in two coupled
Josephson junctions. We show that when the velocity of the moving FL exceeds
certain values , sharp resonances arise in the system which are
related to the excitation of the optical and acoustic collective modes. In the
interval a reconstruction of the FL occurs. We also establish that
one can excite localized nonlinear distortions (dislocations) which may
propagate through the FL and carry an arbitrary magnetic flux.Comment: 4 pages, 3 figures, corected typo
Comment on "Exact results for survival probability in the multistate Landau-Zener model"
We correct the proof of Brundobler-Elser formula (BEF) provided in [2004
\textit{J. Phys. B: At. Mol. Opt. Phys.} \textbf{37} 4069] and continued in
Appendix of [2005 \textit{J. Phys. B: At. Mol. Opt. Phys.} \textbf{38} 907].
After showing that some changes of variables employed in these articles are
used erroneously, we propose an alternative change of variables which solves
the problem. In our proof, we reveal the connection between the BEF for a
general -level Landau-Zener system and the exactly solvable bow-tie model.
The special importance of the diabatic levels with maximum/minimum slope is
emphasized throughout.Comment: 10 page
Towards a Novel no-hair Theorem for Black Holes
We provide strong numerical evidence for a new no-scalar-hair theorem for
black holes in general relativity, which rules out spherical scalar hair of
static four dimensional black holes if the scalar field theory, when coupled to
gravity, satisfies the Positive Energy Theorem. This sheds light on the
no-scalar-hair conjecture for Calabi-Yau compactifications of string theory,
where the effective potential typically has negative regions but where
supersymmetry ensures the total energy is always positive. In theories where
the scalar tends to a negative local maximum of the potential at infinity, we
find the no-scalar-hair theorem holds provided the asymptotic conditions are
invariant under the full anti-de Sitter symmetry group.Comment: 25 pages, 11 figure
Pion Polarizability in the NJL model and Possibilities of its Experimental Studies in Coulomb Nuclear Scattering
The charge pion polarizability is calculated in the Nambu-Jona-Lasinio model,
where the quark loops (in the mean field approximation) and the meson loops (in
the approximation) are taken into account. We show that quark loop
contribution dominates, because the meson loops strongly conceal each other.
The sigma-pole contribution plays the main role and
contains strong t-dependence of the effective pion polarizability at the region
. Possibilities of experimental test of this sigma-pole
effect in the reaction of Coulomb Nuclear Scattering are estimated for the
COMPASS experiment.Comment: 11 pages, 8 figure
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