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V. Rossetto

Publications and source records attributed to V. Rossetto.

6 recordsLinked to original sources
arXiv2004

Geometric depolarization in patterns formed by backscattered light

We formulate a framework for the depolarization of linearly polarized backscattered light based on the concept of geometric phase, {\it i.e} Berry's phase. The predictions of this theory are applied to the patterns formed by backscattered light between crossed or parallel polarizers. This theory should be particularly adapted to the situation in which polarized light is scattered many times but predominantly in the forward direction. We apply these ideas to the patterns which we obtained experimentally with backscattered polarized light from a colloidal suspension.

cond-mat.dis-nn↗
arXiv2003

Writhing Geometry of Open DNA

Motivated by recent experiments on DNA torsion-force-extension characteristics we consider the writhing geometry of open stiff molecules. We exhibit a cyclic motion which allows arbitrarily large twisting of the end of a molecule via an activated process. This process is suppressed for forces larger than femto-Newtons which allows us to show that experiments are sensitive to a generalization of the Calugareanu-White formula for the writhe. Using numerical methods we compare this formulation of the writhe with recent analytic calculations.

physics.bio-ph↗
arXiv2003

Local Simulation Algorithms for Coulomb Interaction

Long ranged electrostatic interactions are time consuming to calculate in molecular dynamics and Monte-Carlo simulations. We introduce an algorithmic framework for simulating charged particles which modifies the dynamics so as to allow equilibration using a local Hamiltonian. The method introduces an auxiliary field with constrained dynamics so that the equilibrium distribution is determined by the Coulomb interaction. We demonstrate the efficiency of the method by simulating a simple, charged lattice gas.

cond-mat.stat-mech↗
arXiv2001

Geometric phases and polarization patterns in multiple light scattering

Multiple light scattering is widely used to characterize dense colloidal systems as well as in deep tissue imaging; experiments are often interpreted via a theory of diffusion of the light intensity within a sample, neglecting the vector nature of the electromagnetic wave. Recent experiments on diffuse backscattering with linearly polarized light from colloidal suspensions of micron size particles were found to display strong intensity variations with fourfold rotational symmetry when observed through an arbitrarily oriented linear analyzer. We show that these polarization patterns are manifestations of a Berry phase of the multiple scattered beam.

cond-mat.soft↗
arXiv2001

Writhing Photons and Berry Phases in Diffusive Wave Scattering

We study theoretically the polarization state of light in multiple scattering media in the limit of weak gradients in refractive index. Linearly polarized photons are randomly rotated due to the Berry phase associated with the scattering path. For circularly polarized light independent speckle patterns are found for the two helical states. The statistics of the geometric phase is related to the writhe distribution of semiflexible polymers such as DNA.

cond-mat.soft↗