Norm attainment of a class of block operator matrices

Kangjian Wu, Jiayu Ling, Qingxiang Xu

Given complex numbers $a,b,c$ and a non-negative continuous function $\phi$ defined on $[0,+\infty )$, consider the $2\times 2$ matrix $$ M_t = \begin{pmatrix} a & t \\ ct & bφ(t)…