Decay of correlations and control of chaotic billiards (Q1376736)

Billiards are dynamical systems with elastic reflections within a region which has a piecewise smooth boundary. In the paper, which is of experimental nature, the billiard is a square with a disc of radius \(R\) placed at its center. Moreover, there is a small hole at one segment of the boundary. By the activity \(A(t)\) is meant the number of particles leaving the system at time \(t:A(t)= -dN(t)/dt\), where \(N(t)\) is the number of particles in the system at time \(t\). As chaos control is used the sinusoidal perturbation to the disc to change the activity \(A(t)\).