A simple model of a rubber band is a one-dimensional horizontal chain consisting of N linked segments ??Each segment can be in one of two possible states: horizontal, with length a, or vertical, with length 0. The rubber band is in thermal equilibrium with a reservoir at temperature t.
Determine the exact multiplicity function g(N,n) giving the number of states with precisely n horizontal links?
What is the exact probability P(n) to find the system in a state with n horizontal links?