arXiv subjects

Chaviva Sirote

Publications and source records attributed to Chaviva Sirote.

2 recordsLinked to original sources

arXiv2023

Bloch Oscillations, Landau-Zener Transition, and Topological Phase Evolution in a Pendula Array

We experimentally and theoretically study the dynamics of a one-dimensional array of pendula with a mild spatial gradient in their self-frequency and where neighboring pendula are connected with weak and alternating coupling. We map their dynamics to the topological Su-Schrieffer-Heeger (SSH) model of charged quantum particles on a lattice with alternating hopping rates in an external electric field. By directly tracking the dynamics of a wavepacket in the bulk of the lattice, we observe Bloch oscillations, Landau-Zener transitions, and coupling between the isospin (i.e. the inner wave function distribution within the unit cell) and the spatial degrees of freedom (the distribution between unit cells). We then use Bloch oscillations in the bulk to directly measure the non-trivial global topological phase winding and local geometric phase of the band. We measure an overall evolution of 3.1 $\pm$ 0.2 radians for the geometrical phase during the Bloch period, consistent with the expected Zak phase of $π$. Our results demonstrate the power of classical analogs of quantum models to directly observe the topological properties of the band structure, and sheds light on the similarities and the differences between quantum and classical topological effects.

cond-mat.mes-hall↗

arXiv2021

Mean-field interactions between living cells in linear and nonlinear elastic matrices

Living cells respond to mechanical changes in the matrix surrounding them by applying contractile forces that are in turn transmitted to distant cells. We calculate the mechanical work that each cell performs in order to deform the matrix, and study how that energy changes when a contracting cell is surrounded by other cells with similar properties and behavior. We consider simple effective geometries for the spatial arrangement of cells, with spherical and with cylindrical symmetries, and model the presence of neighboring cells by imposing zero-displacement at some distance from the cell, which represents the surface of symmetry between neighboring cells. In linear elastic matrices, we analytically study the dependence of the resulting interaction energy on the geometry and on the stiffness and regulatory behavior of the cells. For cells that regulate the active stress that they apply, in spherical geometry, the deformation inside the cell is pure compression thus the interaction depends only on their bulk modulus, while in cylindrical geometries the deformation includes also shear and the interaction depends also on their shear modulus. In nonlinear, strain stiffening matrices, our numerical solutions and analytical approximations show how in the presence of other cells, cell contraction is limited due to the divergence of the shear stress.

cond-mat.soft↗