8,238 research outputs found
Smearing of Coulomb Blockade by Resonant Tunneling
We study the Coulomb blockade in a grain coupled to a lead via a resonant
impurity level. We show that the strong energy dependence of the transmission
coefficient through the impurity level can have a dramatic effect on the
quantization of the grain charge. In particular, if the resonance is
sufficiently narrow, the Coulomb staircase shows very sharp steps even if the
transmission through the impurity at the Fermi energy is perfect. This is in
contrast to the naive expectation that perfect transmission should completely
smear charging effects.Comment: 4 pages, 3 figure
Dynamical conductance in the two-channel Kondo regime of a double dot system
We study finite-frequency transport properties of the double-dot system
recently constructed to observe the two-channel Kondo effect [R. M. Potok et
al., Nature 446, 167 (2007)]. We derive an analytical expression for the
frequency-dependent linear conductance of this device in the Kondo regime. We
show how the features characteristic of the 2-channel Kondo quantum critical
point emerge in this quantity, which we compute using the results of conformal
field theory as well as numerical renormalization group methods. We determine
the universal cross-over functions describing non-Fermi liquid vs. Fermi liquid
cross-overs and also investigate the effects of a finite magnetic field.Comment: 11 pages in PRB forma
Vanishing Point Detection with Direct and Transposed Fast Hough Transform inside the neural network
In this paper, we suggest a new neural network architecture for vanishing
point detection in images. The key element is the use of the direct and
transposed Fast Hough Transforms separated by convolutional layer blocks with
standard activation functions. It allows us to get the answer in the
coordinates of the input image at the output of the network and thus to
calculate the coordinates of the vanishing point by simply selecting the
maximum. Besides, it was proved that calculation of the transposed Fast Hough
Transform can be performed using the direct one. The use of integral operators
enables the neural network to rely on global rectilinear features in the image,
and so it is ideal for detecting vanishing points. To demonstrate the
effectiveness of the proposed architecture, we use a set of images from a DVR
and show its superiority over existing methods. Note, in addition, that the
proposed neural network architecture essentially repeats the process of direct
and back projection used, for example, in computed tomography.Comment: 9 pages, 9 figures, submitted to "Computer Optics"; extra experiment
added, new theorem proof added, references added; typos correcte
Quantum Charge Fluctuations in a Superconducting Grain
We consider charge quantization in a small superconducting grain that is
contacted by a normal-metal electrode and is controlled by a capacitively
coupled gate. At zero temperature and zero conductance between the grain
and the electrode, the charge as a function of the gate voltage
changes in steps. The step height is if , where and
are, respectively, the superconducting gap and the charging energy of the
grain. Quantum charge fluctuations at finite conductance remove the
discontinuity in the dependence of on and lead to a finite step width
. The resulting shape of the Coulomb blockade staircase is
of a novel type. The grain charge is a continuous function of while the
differential capacitance, , has discontinuities at certain values of
the gate voltage. We determine analytically the shape of the Coulomb blockade
staircase also at non-zero temperatures.Comment: 12 pages, 3 figure
A solution of a problem of Sophus Lie: Normal forms of 2-dim metrics admitting two projective vector fields
We give a complete list of normal forms for the 2-dimensional metrics that
admit a transitive Lie pseudogroup of geodesic-preserving transformations and
we show that these normal forms are mutually non-isometric. This solves a
problem posed by Sophus Lie.Comment: This is an extended version of the paper that will appear in Math.
Annalen. Some typos were corrected, references were updated, title was
changed (as in the journal version). 31 page
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