Condensed Matter Theory

Abstract:

The simple model of a low Reynolds number swimmer made from three spheres that are connected by two arms is considered in its general form and analyzed. The swimming velocity, force-velocity response, power consumption, and efficiency of the swimmer are calculated both for general deformations and also for specific model prescriptions. The role of noise and coherence in the stroke cycle is also discussed.

Abstract:

The coupling between corrugated surfaces due to the lateral Casimir force is employed to propose a nanoscale mechanical device composed of two racks and a pinion. The noncontact nature of the interaction allows for the system to be made frustrated by choosing the two racks to move in the same direction and forcing the pinion to choose between two opposite directions. This leads to a rich and sensitive phase behavior, which makes the device potentially useful as a mechanical {\em sensor} or {\em amplifier}. The device could also be used to make a mechanical {\em clock} signal of tunable frequency.

Abstract:

We construct a family of BCS paired composite-fermion wave functions that generalize but remain in the same topological phase as the Moore-Read Pfaffian state for the half-filled Landau level. It is shown that for a wide range of experimentally relevant interelectron interactions, the ground state can be very accurately represented in this form. © 2008 The American Physical Society.