Condensed Matter Theory

Abstract:

In an attempt to understand the origin of relaxor ferroelectricity, it is shown that interesting behavior of the onset of nonergodicity and of precursor nanodomains, found in first-principles simulations of the relaxor alloy Ba(Zr(1-x)Ti(x))O(3), can easily be understood within a simple mapping to a soft pseudospin glass.

Abstract:

We consider the tracer diffusion Drr that arises from the run-and-tumble motion of low Reynolds number swimmers, such as bacteria. Assuming a dilute suspension, where the bacteria move in uncorrelated runs of length λ, we obtain an exact expression for Drr for dipolar swimmers in three dimensions, hence explaining the surprising result that this is independent of λ. We compare Drr to the contribution to tracer diffusion from entrainment. © 2013 American Physical Society.

Abstract:

We present a number of arguments to demonstrate that a quantum analog of the Cherenkov effect occurs when two nondispersive half spaces are in relative motion. We show that they experience friction beyond a threshold velocity which, in their center-of-mass frame, is the phase speed of light within their medium, and the loss in mechanical energy is radiated through the medium before getting fully absorbed in the form of heat. By deriving various correlation functions inside and outside the two half spaces, we explicitly compute this radiation and discuss its dependence on the reference frame. © 2013 American Physical Society.