Subdifferential of the $\mathcal{B}(\mathcal{H},\mathcal{K})$ norm, and approximate orthogonality

Priyanka Grover, Krishna Kumar Gupta, Susmita Seal

We present an expression for the right hand derivative of the $\mathcal{B}(\mathcal{H},\mathcal{K})$ norm generalizing the result for $\mathcal{K}=\mathcal{H}$ in [D. J. Ke$\check{\mathrm{c}}$ki$\grav…