Kronecker delta
In mathematics, the Kronecker delta is a function of two variables, which is 1 if they are equal, and 0 otherwise. It is written as the symbol δij, and treated as a notational shorthand rather than a function.
- <math>\delta_{ij} = \left\{\begin{matrix}
1 & \mbox{if } i=j \\
0 & \mbox{if } i \ne j \end{matrix}\right.<math>
It is named after mathematician Leopold Kronecker (1823-1891).
It is used in many areas of mathematics. For example, in linear algebra, the identity matrix can be written as:
- ( δi j )
See also Levi-Civita symbol, Dirac delta function.
