Exact dynamics of a reaction-diffusion model with spatially alternating rates

We present the exact solution for the full dynamics of a nonequilibrium spin chain and its dual reaction-diffusion model, for arbitrary initial conditions. The spin chain is driven out of equilibrium by coupling alternating spins to two thermal baths at different temperatures. In the reaction-diffusion model, this translates into spatially alternating rates for particle creation and annihilation, and even negative ``temperatures'' have a perfectly natural interpretation. Observables of interest include the magnetization, the particle density, and all correlation functions for both models. Two generic types of time-dependence are found: if both temperatures are positive, the magnetization, density and correlation functions decay exponentially to their steady-state values. In contrast, if one of the temperatures is negative, damped oscillations are observed in all quantities. They can be traced to a subtle competition of pair creation and annihilation on the two sublattices. We comment on the limitations of mean-field theory and propose an experimental realization of our model in certain conjugated polymers and linear chain compounds.Comment: 13 pages, 1 table, revtex4 format (few minor typos fixed). Published in Physical Review

Social Constraints on the Direct Perception of Emotions and Intentions

In this paper, we first review recent arguments about the direct perception of the intentions and emotions of others, emphasizing the role of embodied interaction. We then consider a possible objection to the direct perception hypothesis from social psychology, related to phenomena like 'dehumanization' and 'implicit racial bias', which manifest themselves on a basic bodily level. On the background of such data, one might object that social perception cannot be direct since it depends on and can in fact be interrupted by a set of cultural beliefs. We argue, however, that far from threatening the idea of direct perception, these findings clearly contradict the idea of hardwired theory of mind modules. More generally, we suggest that in order to further the understanding of social cognition we must take seriously insights about in-group and out-group distinctions and related phenomena, all of which are currently neglected in the mainstream social cognition literature.Peer reviewe