175 research outputs found
Topological speckles
The time evolution of a topological Su-Schrieffer-Heeger chain is analyzed
through the statistics of speckle patterns. The emergence of topological edge
states dramatically affects the dynamical fluctuations of the wavefunction. The
intensity statistics is found to be described by a family of noncentral
chi-squared distributions, with the noncentrality parameter reflecting on the
degree of edge-state localization. The response of the speckle contrast with
respect to the dimerization of the chain is explored in detail as well as the
role of chiral symmetry-breaking disorder, number of edge states, their energy
gap, and the locations between which the transport occurs. In addition to
providing a venue for speckle customization, our results appeal to the use of
speckle patterns for characterization of nontrivial topological properties.Comment: 6 pages, 4 figure
Random-mass Dirac fermions in an imaginary vector potential: Delocalization transition and localization length
One dimensional system of Dirac fermions with a random-varying mass is
studied by the transfer-matrix methods which we developed recently. We
investigate the effects of nonlocal correlation of the spatial-varying Dirac
mass on the delocalization transition. Especially we numerically calculate both
the "typical" and "mean" localization lengths as a function of energy and the
correlation length of the random mass. To this end we introduce an imaginary
vector potential as suggested by Hatano and Nelson and solve the eigenvalue
problem. Numerical calculations are in good agreement with the results of the
analytical calculations.Comment: 4 page
Synthesis and preliminary ex vivo evaluation of the spasmolytic activity of 1,3-thiazolium- and 1,3,4-thiadiazolium-5-methylthio- and 5-tioacetate derivatives
Seven new compounds have been synthetized in satisfactory yields (51-78 %), through the treatment of mesoionic 1,3-thiazolium-5-thiolate (4a-d) and 1,3,4-thiadiazolium-5-thiolate (10a,b) with chloroacetic acid or methyl iodide: 1,3-thiazolium-5-methylthio- (5a-c), 5-thioacetate (6a,b) and 1,3,4-thiadiazolium-5-methylthio- (11) and 5-thioacetate (12). The structure of the title compounds was elucidated by elemental analysis, IR, 1H and 13C NMR spectroscopy. The newly synthesized compounds 5a, 6a, 11 and 12 were evaluated for their ex vivo spasmolytic potential on four isolated smooth muscles (rat aorta and uterus, guinea pig ileum and trachea) and compared with scopolamine. Some of the compounds exhibited potent spasmolytic activity equal to or stronger than scopolamine
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