We wrote kinetic equation for the average x as
![]() |
(6) |
We can speak only about average properties of f(t). We will
calculate and
. We will average over
equilibrium ensemble.
Averaging (6), we obtain:
![]() |
(7) |
![]() |
(8) |
But we know ! Result:
![]() |
(9) |
![]() |
(10) |
Sometimes the function f(t) is called random noise.
Equation (9) shows that random noise is
-correlated. In other words, all harmonics are present in its
Fourier transform with equal weights
(equation (10)). Such noise is called
white noise (remember rainbow?).
Colored noise: not all harmonics are equal:
How can it be so? What's wrong in our derivation?
![]() |
(11) |
Another interpretation: the -function in
equation (9) is the
-function only
approximately. In fact it is a sharp peak with the width about the
characteristic time of the molecular processes.
© 1997 Boris Veytsman and Michael Kotelyanskii