Explore: Kreĭn Spaces

Tannaka–Krein duality Krein–Milman theorem and Krein–Rutman theorem in functional analysis Krein space Krein's condition for the indeterminacy of the problem

{\displaystyle J} -space) if ( x , y ) {\displaystyle (x,\,y)} is positive definite and K {\displaystyle K} possesses a majorant topology. Krein spaces are named

Moreover, in operator theory there are specific instances of Krein spaces called Pontryagin spaces. Starting in 1952, he worked in optimal control theory.

analysis, the Krein–Rutman theorem is a generalisation of the Perron–Frobenius theorem to infinite-dimensional Banach spaces. It was proved by Krein and Rutman

Fock space of all states prior to the cohomological reduction has an indefinite norm, and so is not a Hilbert space. This requires that a Krein space for

topological vector spaces (LCTVS) or locally convex spaces are examples of topological vector spaces (TVS) that generalize normed spaces. They can be defined

analysis, the Krein–Milman theorem is a proposition about compact convex sets in locally convex topological vector spaces (TVSs). Krein–Milman theorem—A

polynomials and Kravchuk matrix Mark Krein, developed the Tannaka–Krein duality, Krein–Milman theorem and Krein space, Wolf Prize winner Alexander Kronrod

representations on one-dimensional spaces. As explained below, the spectrum  is also naturally a topological space; this is similar to the notion of the

in the plane or other low-dimensional Euclidean spaces, and its dual problem of intersecting half-spaces, are fundamental problems of computational geometry