2D Ising model simulation using Metropolis algorithm.
There is one thing which I don't understand. The difference in energy $\Delta E$ between initial state and new state is:
$\Delta E = 2Js\sum_rs_r$ (btw can someone confirm that pls) where J is constant, s-initial spin and sum is equal to the sum of spins of the nearest neighbours.
The new state is always accepted when $\Delta E<0$ or if $\Delta E>0$ accepted with probability $p=\exp(-\Delta E/k_bT)$.
The question is what happens when $\Delta E = 0$?