Kinetics of active surface-mediated diffusion in spherically symmetric domains

We present an exact calculation of the mean first-passage time to a target on the surface of a 2D or 3D spherical domain, for a molecule alternating phases of surface diffusion on the domain boundary and phases of bulk diffusion. We generalize the results of [J. Stat. Phys. {\bf 142}, 657 (2011)] and consider a biased diffusion in a general annulus with an arbitrary number of regularly spaced targets on a partially reflecting surface. The presented approach is based on an integral equation which can be solved analytically. Numerically validated approximation schemes, which provide more tractable expressions of the mean first-passage time are also proposed. In the framework of this minimal model of surface-mediated reactions, we show analytically that the mean reaction time can be minimized as a function of the desorption rate from the surface.Comment: Published online in J. Stat. Phy

The nonequilibrium potential today: A short review

A brief review is made of the birth and evolution of the “nonequilibrium potential” (NEP) concept. As if providing a landscape for qualitative reasoning were not helpful enough, the NEP adds a quantitative dimension to the qualitative theory of differential equations and provides a global Lyapunov function for the deterministic dynamics. Here we illustrate the usefulness of the NEP to draw results on stochastic thermodynamics: the Jarzynski equality in the Wilson–Cowan model (a population-competition model of the neocortex) and a “thermodynamic uncertainty relation” (TUR) in the KPZ equation (the stochastic field theory of kinetic interface roughening). Additionally, we discuss system-size stochastic resonance in the Wilson–Cowan model and relevant aspects of KPZ phenomenology like the EW–KPZ crossover and the memory of initial conditions

The business firm model of party organisation: cases from Spain and Italy

Discussion of new forms of party organisation have largely focused on the ways in which institutionalised parties have adapted to pressures towards ‘catch-all’ or ‘electoralprofessional’ behaviour. This article examines the ways in which new parties respond to these pressures. A model of the ‘party as business firm’ is generated from rational choice assumptions and it is suggested that such a model can emerge when new party systems are created in advanced societies. Two cases of political parties which resemble the business firm model in important ways are analysed in order to gauge the consequences of this type of party organisation: UCD in Spain and Forza Italia in Italy. On the basis of this analysis it is argued that business firm parties are likely to be electorally unstable and politically incoherent, and also prone to serving particularistic interests