Hadamard (disambiguation)

Hadamard may refer to:


 * Zélie Hadamard (1849–1901), French actress
 * Jacques Hadamard (1865–1963), a French mathematician, whose name is associated with the following topics in mathematics:

Differential geometry

 * Hadamard space, a geodesically complete metric space of non-positive curvature
 * Cartan-Hadamard theorem, a result on the topology of non-positively curved manifolds

Differential equations and dynamical systems

 * Hadamard's method of descent, a method of solving partial differential equations by reducing dimensions
 * Hadamard parametrix construction, a method of solving second order partial differential equations
 * Hadamard's dynamical system, a type of chaotic dynamical system

Complex analysis and convexity

 * Hadamard three-lines theorem: a bound on the maximum modulus complex analytic functions defined on a strip in the complex plane;
 * Hadamard three-circle theorem, a bound on the maximum modulus of complex analytic functions defined on an annulus in the complex plane; closely related to the three-lines theorem;
 * Hadamard factorization theorem, a specific factorization of an entire function of finite order, involving its zeros and the exponential of a polynomial
 * Ostrowski–Hadamard gap theorem, a result on the analytic continuation of lacunary power series
 * Hermite–Hadamard inequality, bounding the integral of convex functions.

Transform calculus

 * Hadamard transform, an example of a generalized class of Fourier transforms
 * Fast Walsh–Hadamard transform, an efficient algorithm to compute the Hadamard transform

Theory of matrices

 * Hadamard matrix, a square matrix whose entries are either +1 or −1 and whose rows are mutually orthogonal
 * Hadamard code, a system used for signal error detection and correction based on Hadamard matrices
 * Hadamard's inequality, a bound on the determinants of matrices.
 * Hadamard product, a name for element-wise multiplication of matrices/

Quantum computing

 * Hadamard gate, a standard quantum gate that generalizes a coin flip.