A remark on condensation of singularities (Q2870977)

Let \(X\) be a quasi-Banach space and let \(\{T_{n,m}\}\) be a double sequence of bounded homogenous operators with values in quasi-normed linear spaces. The author gives a proof of the principle of condensation of singularities, under additional hypothesis of subadditivity of the norm on the vectors \(T_{n,m}(x+y)\), \(T_{n,m}(x)\), \(T_{n,m}(y)\) for all \(x,y \in X\).