# Wiener equation

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A simple mathematical representation of Brownian motion, the **Wiener equation**, named after Norbert Wiener,^{[1]} assumes the current velocity of a fluid particle fluctuates randomly:

where **v** is velocity, **x** is position, *d/dt* is the time derivative, and *g(t)* may for instance be white noise.

Since velocity changes instantly in this formalism, the *Wiener equation* is not suitable for short time scales. In those cases, the Langevin equation, which looks at particle acceleration, must be used.

## References[edit]

**^**Pesi R. Masani (6 December 2012).*Norbert Wiener 1894–1964*. Birkhäuser. pp. 134–. ISBN 978-3-0348-9252-0.