  We derive a differential-integral equation akin to the Hegselmann-Krause
model of opinion dynamics, and propose a particle method for solving the
equation. Numerical experiments demonstrate second-order convergence of the
method in a weak sense. We also show that our differential-integral equation
can equivalently be stated as a system of differential equations. An
integration-by-parts argument that would typically yield an energy dissipation
inequality in physical problems then yields a concentration inequality, showing
that a natural measure of concentration increases monotonically.
