26,785 research outputs found
A class of cubic Rauzy Fractals
In this paper, we study arithmetical and topological properties for a class
of Rauzy fractals given by the polynomial
where is an integer. In particular, we prove the number of neighbors
of in the periodic tiling is equal to . We also give
explicitly an automaton that generates the boundary of . As a
consequence, we prove that is homeomorphic to a topological
disk
Bifurcations from families of periodic solutions in piecewise differential systems
Consider a differential system of the form where
and are piecewise
functions and -periodic in the variable . Assuming that the unperturbed
system has a -dimensional submanifold of periodic solutions
with , we use the Lyapunov-Schmidt reduction and the averaging theory to
study the existence of isolated -periodic solutions of the above
differential system
Noise properties of two single electron transistors coupled by a nanomechanical resonator
We analyze the noise properties of two single electron transistors (SETs)
coupled via a shared voltage gate consisting of a nanomechanical resonator.
Working in the regime where the resonator can be treated as a classical system,
we find that the SETs act on the resonator like two independent heat baths. The
coupling to the resonator generates positive correlations in the currents
flowing through each of the SETs as well as between the two currents. In the
regime where the dynamics of the resonator is dominated by the back-action of
the SETs, these positive correlations can lead to parametrically large
enhancements of the low frequency current noise. These noise properties can be
understood in terms of the effects on the SET currents of fluctuations in the
state of a resonator in thermal equilibrium which persist for times of order
the resonator damping time.Comment: Accepted for publication in Phys. Rev.
Evidence of spontaneous spin polarized transport in magnetic nanowires
The exploitation of the spin in charge-based systems is opening revolutionary
opportunities for device architecture. Surprisingly, room temperature
electrical transport through magnetic nanowires is still an unresolved issue.
Here, we show that ferromagnetic (Co) suspended atom chains spontaneously
display an electron transport of half a conductance quantum, as expected for a
fully polarized conduction channel. Similar behavior has been observed for Pd
(a quasi-magnetic 4d metal) and Pt (a non-magnetic 5d metal). These results
suggest that the nanowire low dimensionality reinforces or induces magnetic
behavior, lifting off spin degeneracy even at room temperature and zero
external magnetic field.Comment: 4 pages, 3 eps fig
The Einstein-Hilbert Lagrangian Density in a 2-dimensional Spacetime is an Exact Differential
Recently Kiriushcheva and Kuzmin claimed to have shown that the
Einstein-Hilbert Lagrangian cannot be written in any coordinate gauge as an
exact differential in a 2-dimensional spacetime. Since this is contrary to
other statements on the subject found in the literature, as e.g., by Deser and
Jackiw, Jackiw, Grumiller, Kummer and Vassilevich it is necessary to do decide
who has reason. This is done in this paper in a very simply way using the
Clifford bundle formalism. In this version we added Section 18 which discusses
a recent comment on our paper just posted by Kiriushcheva and Kuzmin.Comment: 11 pages, Misprints in some equations have been corrected; four new
references have been added, Section 18 adde
Generalization of Dirac Non-Linear Electrodynamics, and Spinning Charged Particles
In this note we generalized the Dirac non-linear electrodynamics, by
introducing two potentials (namely, the vector potential A and the
pseudo-vector potential gamma^5 B of the electromagnetic theory with charges
and magnetic monopoles) and by imposing the pseudoscalar part of the product
omega.omega* to be zero, with omega = A + gamma^5 B. We show that the field
equations of such a theory possess a soliton-like solution which can represent
a priori a "charged particle", since it is endowed with a Coulomb field plus
the field of a magnetic dipole. The rest energy of the soliton is finite, and
the angular momentum stored in its electromagnetic field can be identified
--for suitable choices of the parameters-- with the spin of the charged
particle. Thus this approach seems to yield a classical model for the charged
(spinning) particle, which does not meet the problems met by earlier attempts
in the same direction.Comment: standard LaTeX file; 16 pages; it is a corrected version of a paper
appeared in Found. Phys. (issue in honour of A.O.Barut) 23 (1993) 46
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