arXiv subjects

Henri Orland

Publications and source records attributed to Henri Orland.

60 records · Page 4Linked to original sources

arXiv2002

The Random Fuse Network as a Dipolar Magnet

We introduce an approximate mapping between the random fuse network (RFN) and a random field dipolar Ising model (RFDIM). The state of the network damage is associated with a metastable spin configuration. A mean-field treatment, numerical solutions, and heuristic arguments support the broad validity of the approximation and yield a generic phase diagram. At low disorder, the growth of a single unstable `crack' leads to an abrupt global failure. Beyond a critical disorder, the conducting network sustains significant damage before the coalescence of cracks results in global failure.

cond-mat.stat-mech↗

arXiv2000

Bridge Hopping on Conducting Polymers in Solution

Configurational fluctuations of conducting polymers in solution can bring into proximity monomers which are distant from each other along the backbone. Electrons can hop between these monomers across the "bridges" so formed. We show how this can lead to (i) a collapse transition for metallic polymers, and (ii) to the observed dramatic efficiency of acceptor molecules for quenching fluorescence in semiconducting polymers.

cond-mat.soft↗

arXiv1999

Beyond Poisson-Boltzmann: Fluctuations and Correlations

We formulate the non-linear field theory for a fluctuating counter-ion distribution in the presence of a fixed, arbitrary charge distribution. The Poisson-Boltzmann equation is obtained as the saddle-point, and the effects of fluctuations and correlations are included by a loop-wise expansion around this saddle point. We show that the Poisson equation is obeyed at each order in the loop expansion and explicitly give the expansion of the Gibbs potential up to two loops. We then apply our formalism to the case of an impenetrable, charged wall, and obtain the fluctuation corrections to the electrostatic potential and counter-ion density to one-loop order without further approximations. The relative importance of fluctuation corrections is controlled by a single parameter, which is proportional to the cube of the counter-ion valency and to the surface charge density. We also calculate effective interactions between charged particles, which reflect counter-ion correlation effects.

cond-mat.soft↗

arXiv1998

The role of the energy gap in protein folding dynamics

The dynamics of folding of proteins is studied by means of a phenomenological master equation. The energy distribution is taken as a truncated exponential for the misfolded states plus a native state sitting below the continuum. The influence of the gap on the folding dynamics is studied, for various models of the transition probabilities between the different states of the protein. We show that for certain models, the relaxation to the native state is accelerated by increasing the gap, whereas for others it is slowed down .

cond-mat.soft↗

arXiv1998

Field theory fo charged fluids and colloids

A systematic field theory is presented for charged systems. The one-loop level corresponds to the classical Debye-Hückel (DH) theory, and exhibits the full hierarchy of multi-body correlations determined by pair-distribution functions given by the screened DH potential. Higher-loop corrections can lead to attractive pair interactions between colloids in asymmetric ionic environments. The free energy follows as a loop-wise expansion in half-integer powers of the density; the resulting two-phase demixing region shows pronounced deviations from DH theory for strongly charged colloids.

cond-mat.stat-mech↗

arXiv1998

A Path Integral Approach to Effective Non-Linear Medium

In this article, we propose a new method to compute the effective properties of non-linear disordered media. We use the fact that the effective constants can be defined through the minimum of an energy functional. We express this minimum in terms of a path integral allowing us to use many-body techniques. We obtain the perturbation expansion of the effective constants to second order in disorder, for any kind of non-linearity. We apply our method to both cases of strong and weak non-linearities. Our results are in agreement with previous ones, and could be easily extended to other types of non-linear problems in disordered systems.

cond-mat.dis-nn↗