Standard map

The standard map (also known as the Chirikov–Taylor map or as the Chirikov standard map) is an area-preserving chaotic map from a square with side ${\displaystyle 2\pi }$ onto itself. It is constructed by a Poincaré's surface of section of the kicked rotator, and is defined by:

where ${\displaystyle p_{n}}$ and ${\displaystyle \theta _{n}}$ are taken modulo ${\displaystyle 2\pi }$.

...
Wikipedia