time, , and is the intensity. The angular brackets denote the expected value operator, which in some texts is denoted by a capital .

At short time delays, the correlation is high because the particles do not have a chance to move to a great extent from the initial state that they were in. The two signals are thus essentially unchanged when compared after only a very short time interval. As the time delays become longer, the correlation decays exponentially, meaning that, after a long period has