Wavenumber Wavenumber In the physical sciences, the wavenumber (also wave number or repetency) is the spatial frequency of a wave, measured in cycles per unit distance or radians per unit distance. Whereas temporal frequency can be thought of as the number of waves per unit time, wavenumber is the number of waves per unit distance. In multidimensional systems, the wavenumber is the magnitude of the wave vector. The space of wave vectors is called reciprocal space. Wave numbers and wave vectors play an essential role in optics and the physics of wave scattering, such as X-ray diffraction, neutron diffraction, and elementary
Parity of a permutation of formula_1 into disjoint cycles, which can be composed in any order because they commute. A cycle formula_49 involving formula_50 points can always be obtained by composing formula_51 transpositions (2-cycles): so call formula_51 the "size" of the cycle, and observe that, under this definition, transpositions are cycles of size 1. From a decomposition into formula_54 disjoint cycles we can obtain a decomposition of formula_1 into formula_56 transpositions, where formula_57 is the size of the th cycle. The number formula_58 is called the discriminant of formula_1, and can also be computed as if we take care to include the fixed points