14,859 research outputs found
The Scaling of the Anomalous Hall Effect in the Insulating Regime
We develop a theoretical approach to study the scaling of anomalous Hall
effect (AHE) in the insulating regime, which is observed to be
in experiments over a large
range of materials. This scaling is qualitatively different from the ones
observed in metals. Basing our theory on the phonon-assisted hopping mechanism
and percolation theory, we derive a general formula for the anomalous Hall
conductivity, and show that it scales with the longitudinal conductivity as
with predicted to be
, quantitatively in agreement with the experimental
observations. Our result provides a clearer understanding of the AHE in the
insulating regime and completes the scaling phase diagram of the AHE.Comment: 4 pages, 4 figures, plus the supplementary information. Minor
revisions made according to Referee report
On fuzzy BCC-ideals over a t-norm
Using a t-norm T, the notion of T-fuzzy BCC-ideals of BCC-algebras is introduced, and some of their properties are investigated.
Connections between different types of fuzzy BCC-ideals induced by
t-norms are described
Diffusion-limited loop formation of semiflexible polymers: Kramers theory and the intertwined time scales of chain relaxation and closing
We show that Kramers rate theory gives a straightforward, accurate estimate
of the closing time of a semiflexible polymer that is valid in cases
of physical interest. The calculation also reveals how the time scales of chain
relaxation and closing are intertwined, illuminating an apparent conflict
between two ways of calculating in the flexible limit.Comment: Europhys. Lett., 2003 (in press). 8 pages, 3 figures. See also,
physics/0101087 for physicist's approach to and the importance of
semiflexible polymer looping, in DNA replicatio
Optimal quantum circuit synthesis from Controlled-U gates
From a geometric approach, we derive the minimum number of applications
needed for an arbitrary Controlled-Unitary gate to construct a universal
quantum circuit. A new analytic construction procedure is presented and shown
to be either optimal or close to optimal. This result can be extended to
improve the efficiency of universal quantum circuit construction from any
entangling gate. Specifically, for both the Controlled-NOT and Double-CNOT
gates, we develop simple analytic ways to construct universal quantum circuits
with three applications, which is the least possible.Comment: 4 pages, 3 figure
Critical currents for vortex defect motion in superconducting arrays
We study numerically the motion of vortices in two-dimensional arrays of
resistively shunted Josephson junctions. An extra vortex is created in the
ground states by introducing novel boundary conditions and made mobile by
applying external currents. We then measure critical currents and the
corresponding pinning energy barriers to vortex motion, which in the
unfrustrated case agree well with previous theoretical and experimental
findings. In the fully frustrated case our results also give good agreement
with experimental ones, in sharp contrast with the existing theoretical
prediction. A physical explanation is provided in relation with the vortex
motion observed in simulations.Comment: To appear in Physical Review
Neutrino oscillations in de Sitter space-time
We try to understand flavor oscillations and to develop the formulae for
describing neutrino oscillations in de Sitter space-time. First, the covariant
Dirac equation is investigated under the conformally flat coordinates of de
Sitter geometry. Then, we obtain the exact solutions of the Dirac equation and
indicate the explicit form of the phase of wave function. Next, the concise
formulae for calculating the neutrino oscillation probabilities in de Sitter
space-time are given. Finally, The difference between our formulae and the
standard result in Minkowski space-time is pointed out.Comment: 13 pages, no figure
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