Integrated Calendar

It has taken about 30 years for the notion of attractor dynamics to get the attention of the experimental neuroscience community. Now that some are beginning to investigate the more sophisticated idea of continuous attractors, where marginal stability can be used for cognitive operations such as path integration or the prediction of the consequences of one's own actions, it is time to tell the truth about continuous attractors. I will discuss a quantitative approach to the smoothness of the spatial maps that can be established in the CA3 hippocampal network, and suggest that in the space of memories, we may jump more often than slide.

We employed a solid state dewetting technique to produce an array of faceted single crystalline Au particles of sub-micrometer dimensions on the sapphire substrate. The faceted single crystal particles exhibited a profound size and shape stability, even after prolonged anneals in air at the temperatures close to the melting point of gold. The microparticles were tested in compression employing the depth-sensing indentation instruments equipped with the sharp “cube corner” and flat diamond tips. The nanoindentation tests performed with cube corner indenter revealed that plastic deformation compliance of the particles increases with decreasing particles size. Gold thin films of comparable thickness exhibited much higher resistance to plastic deformation than the particles. On the contrary, during the nanoindentation tests performed with the flat diamond punch, small particles exhibited higher yield strength than their large counterparts (smaller is stronger). To understand these differences in the indentation behavior of the microparticles and thin films, we performed atomistic molecular dynamic simulations of the indentation process. The simulations showed that in the case of cube corner indenter the dislocations are nucleated at the interface between the indenter and the particles/films, while in the case of flat punch the nucleation occurs at the corners of the upper particle facet. The dislocations in the particles were short-lived and did not form complex dislocation structures before annihilating at the free surfaces. In the thin film the dislocations accumulated around and beneath the indenter, resulting in complex, sessile dislocation structures contributing to film hardening. We proposed a stress-gradient dislocation nucleation model relating the indentation size effect to stress gradients in the particle along the slip plane.

The nu=5/2 fractional quantum Hall plateau remains the leading candidate for a system realizing non-Abelian anyons in nature. Recent numerical studies point to a picture in which the ground state is spin polarized and the elementary excitations are Charged Spin Textures (CSTs), quasi holes that come with a topologically nontrivial texture of electron spins.
We study the composite CST over the Moore-Read quantum Hall state that arises when a collection of elementary CSTs are moved to the same location. Following an algebraic approach based on the characteristic pair correlations of the Moore-Read state, we find that the resulting CST is set by the fusion sector of the underlying non-Abelian quasiparticles. This phenomenon provides a novel way to read out the quantum register of a non-Abelian topologically ordered phase.