When people sit down for a meal, they don’t think about what to do with their hands when eating. It’s just second nature. Yet, their hands are constantly adapting posture and grip to the cutlery, food ...

Let P and Q be two idempotents on a Hilbert space. In this note, we prove that the invertibility of the linear combination $\lambda_{1}P + \lambda_{2}Q$ is independent of the choice of $\lambda_{i}$, ...

span(A₁, . . . ,An) denotes the linear space spanned by Hilbert space operators A₁, . . . ,An. It is known that if span (A, B) consists of normal operators, then A, B commute. Let MI denote the set of ...