Driven inelastic Maxwell gas in one dimension
  A lattice version of the driven inelastic Maxwell gas is studied in one dimension with periodic boundary conditions. Each site $i$ of the lattice is assigned with a scalar `velocity', $v_i$. Nearest neighbors on the lattice interact, with a rate $\tau_c^{-1}$, according to an inelastic collision rule. External driving, occurring with a rate $\tau_w^{-1}$, sustains a steady state in the system. A set of closed coupled equations for the evolution of the variance and the two-point correlation is found. Steady state values of the variance, as well as spatial correlation functions, are calculated. It is shown exactly that the correlation function decays exponentially with distance, and the correlation length for a large system is determined. Furthermore, the spatio-temporal correlation $C(x,t)=\langle v_i(0) v_{i+x} (t)\rangle$ can also be obtained. We find that there is an interior region $-x^* < x < x^*$, where $C(x,t)$ has a time-dependent form, whereas in the exterior region $|x| > x^*$, the correlation function remains the same as the initial form. $C(x,t)$ exhibits second order discontinuity at the transition points $x=\pm x^*$ and these transition points move away from the $x=0$ with a constant speed. 
V. V. Prasad, Sanjib Sabhapandit, Abhishek Dhar, and Onuttom Narayan
cond-mat.stat-mech