26,147 research outputs found
Bifurcations in the theory of current transfer to cathodes of dc discharges and observations of transitions between different modes
General scenarios of transitions between different spot patterns on
electrodes of dc gas discharges and their relation to bifurcations of
steady-state solutions are analyzed. In the case of cathodes of arc discharges,
it is shown that any transition between different modes of current transfer is
related to a bifurcation of steady-state solutions. In particular, transitions
between diffuse and spot modes on axially symmetric cathodes, frequently
observed in the experiment, represent an indication of the presence of
pitchfork or fold bifurcations of steady-state solutions. Experimental
observations of transitions on cathodes of dc glow microdischarges are analyzed
and those potentially related to bifurcations of steady-state solutions are
identified. The relevant bifurcations are investigated numerically and the
computed patterns are found to conform to those observed in the course of the
corresponding transitions in the experiment
Critical Behavior of a Three-State Potts Model on a Voronoi Lattice
We use the single-histogram technique to study the critical behavior of the
three-state Potts model on a (random) Voronoi-Delaunay lattice with size
ranging from 250 to 8000 sites. We consider the effect of an exponential decay
of the interactions with the distance,, with , and
observe that this system seems to have critical exponents and
which are different from the respective exponents of the three-state Potts
model on a regular square lattice. However, the ratio remains
essentially the same. We find numerical evidences (although not conclusive, due
to the small range of system size) that the specific heat on this random system
behaves as a power-law for and as a logarithmic divergence for
and Comment: 3 pages, 5 figure
Re-entrant magnetic field induced charge and spin gaps in the coupled dual-chain quasi-one dimensional organic conductor Perylene[Pt(mnt)]
An inductive method is used to follow the magnetic field-dependent
susceptibility of the coupled charge density wave (CDW) and spin-Peierls (SP)
ordered state behavior in the dual chain organic conductor
Perylene[Pt(mnt)]. In addition to the coexisting SP-CDW state phase
below 8 K and 20 T, the measurements show that a second spin-gapped phase
appears above 20 T that coincides with a field-induced insulating phase. The
results support a strong coupling of the CDW and SP order parameters even in
high magnetic fields, and provide new insight into the nature of the magnetic
susceptibility of dual-chain spin and charge systems.Comment: 6 pages, 6 figure
Dirac quantization of a nonminimal gauged O(3) sigma model
The (2+1) dimensional gauged O(3) nonlinear sigma model with Chern-Simons
term is canonically quantized. Furthermore, we study a nonminimal coupling in
this model implemented by means of a Pauli-type term. It is shown that the set
of constraints of the model is modified by the introduction of the Pauli
coupling. Moreover, we found that the quantum commutator relations in the
nominimal case is independent of the Chern-Simons coefficient, in contrast to
the minimal one.Comment: 7 pages, to appear in Modern Physics Letters
Quantum key distribution with higher-order alphabets using spatially-encoded qudits
We propose and demonstrate a quantum key distribution scheme in higher-order
-dimensional alphabets using spatial degrees of freedom of photons. Our
implementation allows for the transmission of 4.56 bits per sifted photon,
while providing improved security: an intercept-resend attack on all photons
would induce an error rate of 0.47. Using our system, it should be possible to
send more than a byte of information per sifted photon.Comment: 4 pages, 5 figures. Replaced with published versio
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