Symmetric positive semidefinite closedness
12868
Is the product of symmetric positive semidefinite matrices positive definite?
11911
How to prove the positive definite property of the semidefinite matrix with regularization?
92774
Prove that a linear subspace of $C([0,1])$ is closed
115272
Showing that projections $\mathbb{R}^2 \to \mathbb{R}$ are not closed
41611
Open and closed set in n by n matrices space.
1475
In an incomplete inner product space, is a closed linear subspace equal to the orthogonal complement of its orthogonal complement?
38840
Tightness and Inner Regularity
111911
Dimensions of symmetric and skew-symmetric matrices
7457
Prove that $J^+AJ$ has positive eigenvalues
118417
Is $AA^T$ positive semidefinite?
43584
Separability and normal closure
17159
Proof of Closest Point Theorem in Hilbert Space
128835
Compactness of the set of $n \times n$ orthogonal matrices
73471
Positive semidefinite cone is generated by all rank-$1$ matrices.
47975
Closed cone in the euclidean space $\mathbb{R}^n$
153372
Characterization of positive definite matrix with principal minors
69893
An inner product space and its proper closed subspace with trivial orthogonal complement