Prof Ramin Golestanian

Abstract:

We study the statistical mechanics of double-stranded semi-flexible polymers using both analytical techniques and simulation. We find a transition at some finite temperature, from a type of short range order to a fundamentally different sort of short range order. In the high temperature regime, the 2-point correlation functions of the object are identical to worm-like chains, while in the low temperature regime they are different due to a twist structure. In the low temperature phase, the polymers develop a kink-rod structure which could clarify some recent puzzling experiments on actin.

Abstract:

A path integral formulation is developed for the dynamic Casimir effect. It allows us to study arbitrary deformations in space and time of the perfectly reflecting (conducting) boundaries of a cavity. The mechanical response of the intervening vacuum is calculated to linear order in the frequency-wavevector plane. For a single corrugated plate we find a correction to mass at low frequencies, and an effective shear viscosity at high frequencies; both anisotropic. For two plates there is resonant dissipation for all frequencies greater than the lowest optical mode of the cavity.

Abstract:

We consider directed semiflexible polymers embedded in a fluctuating surface which is governed by either surface tension or bending rigidity. The attractive interactions induced by the fluctuations of the surface reduce the rigidity of the polymers. In particular, it is shown that for arbitrarily stiff parallel polymers, there is a characteristic separation below which they prefer to bend rather than stay linear. The out-of plane fluctuations of the polymer, screen out the long-range fluctuation-induced forces, resulting in only a short-ranged effective attraction.

Abstract:

For rival theories within the framework of the test theory of Mansouri - Sexl a geometrical setting in terms of Finsler geometry has been found. It is shown that the time dilation and length contraction parameters measure the deviation from a Riemannian geometry.