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Thestandard map (also known as theChirikov–Taylor map or as theChirikov standard map) is an area-preservingchaotic map from a square with side onto itself.[1] It is constructed by aPoincaré's surface of section of thekicked rotator, and is defined by:
where and are taken modulo.
The properties of chaos of the standard map were established byBoris Chirikov in 1969.
This map describes thePoincaré's surface of section of the motion of a simple mechanical system known as thekicked rotator. The kicked rotator consists of a stick that is free of the gravitational force, which can rotate frictionlessly in a plane around an axis located in one of its tips, and which is periodically kicked on the other tip.
The standard map is a surface of section applied by astroboscopic projection on the variables of the kicked rotator.[1] The variables and respectively determine the angular position of the stick and its angular momentum after then-th kick. The constantK measures the intensity of the kicks on the kicked rotator.
Thekicked rotator approximates systems studied in the fields ofmechanics of particles,accelerator physics,plasma physics, andsolid state physics. For example, circularparticle accelerators accelerate particles by applying periodic kicks, as they circulate in the beam tube. Thus, the structure of the beam can be approximated by the kicked rotor. However, this map is interesting from a fundamental point of view in physics and mathematics because it is a very simple model of a conservative system that displaysHamiltonian chaos. It is therefore useful to study the development of chaos in this kind of system.
For the map is linear and only periodic and quasiperiodicorbits are possible. When plotted inphase space (the θ–p plane), periodic orbits appear as closed curves, and quasiperiodic orbits as necklaces of closed curves whose centers lie in another larger closed curve. Which type of orbit is observed depends on the map's initial conditions.
Nonlinearity of the map increases withK, and with it the possibility to observechaotic dynamics for appropriate initial conditions. This is illustrated in the figure, which displays a collection of different orbits allowed to the standard map for various values of. All the orbits shown are periodic or quasiperiodic, with the exception of the green one that is chaotic and develops in a large region of phase space as an apparently random set of points. Particularly remarkable is the extreme uniformity of the distribution in the chaotic region, although this can be deceptive: even within the chaotic regions, there are an infinite number of diminishingly small islands that are never visited during iteration, as shown in the close-up.
The standard map is related to thecircle map, which has a single, similar iterated equation:
as compared to
for the standard map, the equations reordered to emphasize similarity. In essence, the circle map forces the momentum to a constant.