13,550 research outputs found
Time-Reversal Symmetry Breaking and Decoherence in Chaotic Dirac Billiards
In this work, we perform a statistical study on Dirac Billiards in the
extreme quantum limit (a single open channel on the leads). Our numerical
analysis uses a large ensemble of random matrices and demonstrates the
preponderant role of dephasing mechanisms in such chaotic billiards. Physical
implementations of these billiards range from quantum dots of graphene to
topological insulators structures. We show, in particular, that the role of
finite crossover fields between the universal symmetries quickly leaves the
conductance to the asymptotic limit of unitary ensembles. Furthermore, we show
that the dephasing mechanisms strikingly lead Dirac billiards from the extreme
quantum regime to the semiclassical Gaussian regime
Characterizing neuromorphologic alterations with additive shape functionals
The complexity of a neuronal cell shape is known to be related to its
function. Specifically, among other indicators, a decreased complexity in the
dendritic trees of cortical pyramidal neurons has been associated with mental
retardation. In this paper we develop a procedure to address the
characterization of morphological changes induced in cultured neurons by
over-expressing a gene involved in mental retardation. Measures associated with
the multiscale connectivity, an additive image functional, are found to give a
reasonable separation criterion between two categories of cells. One category
consists of a control group and two transfected groups of neurons, and the
other, a class of cat ganglionary cells. The reported framework also identified
a trend towards lower complexity in one of the transfected groups. Such results
establish the suggested measures as an effective descriptors of cell shape
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