An 
complex matrix 
is called indefinite if nonzero vectors 
and 
exist such that
 |
where 
denotes the conjugate transpose.
A matrix 
may be tested to see if it is indefinite in the Wolfram
Language using IndefiniteMatrixQ[m].
Indefinite Matrix
See also
Determinant, Eigenvalue, Hermitian Matrix, Matrix, Negative Definite Matrix, Negative Semidefinite Matrix, Positive Definite Matrix, Positive Eigenvalued Matrix, Positive Semidefinite MatrixExplore with Wolfram|Alpha
References
Horn, R. A. and Johnson, C. R. Matrix Analysis, repr. with corr. Cambridge, England: Cambridge University Press, p. 397, 1987.Referenced on Wolfram|Alpha
Indefinite MatrixCite this as:
Weisstein, Eric W. "Indefinite Matrix." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/IndefiniteMatrix.html