New posts in Positive Semidefinite

What is the image of $x^{\rm T}Qx\le 1$ under a linear map $x \mapsto Cx$?

Prove that V is an identity operator

Positive-definiteness of matrix with $|a_{ij}| \leq \frac{1}{ij}$

Convexity of $\{x\in \mathbb R^n,\;x^TAx\leq t\}$ for all $t$ implies that $A$ is p.s.d.

Proving a symmetric Cauchy matrix is positive semidefinite

An elegant proof for a claim about orthogonal and positive-definite matrices

Is there any intuition why the following matrix is positive semidefinite?

Is this type of matrix always positive semidefinite?

$k\sum v_i v_i^T-\big(\sum v_i\big)\big(\sum v_i^T\big)\succeq 0$

Parametrization of unitary matrices