On Abstract Convexity with Respect to a Certain Quadratic Coupling Function: Subsets
<jats:p> We investigate abstract convexity generated by the coupling function <jats:inline-formula> <jats:alternatives> <jats:tex-math notation="LaTeX">\varphi(x,A)=|A[x]^2|,\quad x\in \mathbb{R}^n,\ A\in \mathcal{L}^2_{sym}(\mathbb{R...