Spread of a matrix

In mathematics, and more specifically matrix theory, the spread of a matrix is the largest distance in the complex plane between any two eigenvalues of the matrix.
Definition.
Let formula_1 be a square matrix with eigenvalues formula_2. That is, these values formula_3 are the complex numbers such that there exists a vector formula_4 on which formula_1 acts by scalar multiplication:
Then the spread of formula_1 is the non-negative number