Anharmonicity
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Anharmonicity is the deviation of a system from being a harmonic oscillator. An oscillator that is not oscillating in simple harmonic motion is known as an anharmonic oscillator where the system can be approximated to a harmonic oscillator and the anharmonicity can be calculated using perturbation theory. If the anharmonicity is large then other numerical techniques have to be used.
[edit] Anharmonic ratio (cross-ratio)
If A, B, C, D all lie on a straight line then the anharmonic ratio is
In the complex plane the anharmonic ratio is
- There are six distinct anharmonic ratios depending on the order of which the points are chosen.
- Anharmonicity plays a role in lattice and molecular vibrations, in quantum oscillations, and in Acoustics.
