These are things named after Jacques Hadamard (1865–1963), a French mathematician. (For references, see the respective articles.)
Theorems, lemmas, and conjectures
Many of these results are sometimes called "Hadamard's theorem".
Cartan–Hadamard theorem, a statement in Riemannian geometry concerning the structure of complete Riemannian manifolds of non-positive sectional curvature
Cartan–Hadamard conjecture, an open problem in Riemannian geometry and geometric measure theory concerning the generalization of the classical isoperimetric inequality to spaces of nonpositive sectional curvature
Cauchy–Hadamard theorem, a statement in complex analysis describing the radius of convergence of a power series
Hadamard's inequality, a bound on the determinant of a matrix whose entries are complex numbers in terms of the lengths of its column vectors
Hermite–Hadamard inequality, a bound on the mean value of a convex function in an interval in terms of the value it takes at the mid-point and ends of interval
Hadamard's lemma, a result closely related to the first-order term in Taylor's theorem
Ostrowski–Hadamard gap theorem concerning the analytic continuation of complex power series
Hadamard three-circle theorem, concerning the maxima of holomorphic functions within concentric circles in the complex plane.
Hadamard three-lines theorem, concerning the maxima of holomorphic functions defined in regions bounded by parallel lines in the complex plane.
Hadamard's embedding theorem [ru]
Mathematical objects and definitions
Hadamard product:
entry-wise matrix multiplication
an infinite product expansion for the Riemann zeta function
Hadamard code
Hadamard's dynamical system
Hadamard manifold
Hadamard matrix
Hadamard space
Hadamard Transform and Hadamard gate
Hadamard variance
Hadamard's gamma function
Equations, problems, and methods
Hadamard–Rybczynski equation
Hadamard's maximal determinant problem
Hadamard's method of descent
Hadamard regularization
External links
Encyclopedia of Math: Hadamard theorem
Undergraduate Texts in Mathematics
Graduate Studies in Mathematics
Hellenica World - Scientific Library
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