Condensed Matter Theory

Abstract:

We investigate the effects of polymer chains and nanoparticles on the deformation of a droplet in shear and extensional flow using computational modeling that accounts for both the solid and fluid phases explicitly. We show that under shear flow, both the nanoparticles and the encapsulated polymers reduce the shear-induced deformation of the droplet at intermediate capillary numbers. At high capillary numbers, however, long polymer chains can induce the breakup of the droplet. We find that the latter behavior is dependent on the nature of the imposed flow. Specifically, under extensional flow, long polymers inhibit the droplet breakup and reduce deformation. Overall, the findings provide guidelines for tailoring the stability of filled droplets under an imposed flow, and thus, the results can provide useful design rules in a range of technological applications. © 2009 American Institute of Physics.

Abstract:

We study the low temperature dynamics of the classical Heisenberg antiferromagnet with nearest neighbor interaction on the frustrated pyrochlore lattice. We present extensive results for the wave vector and frequency dependence of the dynamical structure factor, obtained from simulations of the precessional dynamics. We also construct a solvable stochastic model for dynamics with conserved magnetization, which accurately reproduces most features of the precessional results. Spin correlations relax at a rate independent of the wave vector and proportional to the temperature.

Abstract:

We propose an experiment to explore the magnetic phase transitions in interacting fermionic Hubbard systems and describe how to obtain the ferromagnetic phase diagram of itinerant-electron systems from these observations. In addition, signatures of ferromagnetic correlations in the observed ground states are found: for large trap radii (trap radius RT >4, in units of coherence length ξ), ground states are topological in nature-a "skyrmion" in two dimension, and a "hedgehog" in three dimension. © 2009 The American Physical Society.