All Questions

This is a follow-up to this question on p-norms of tuples of operators. Consider $\left[\begin{matrix} A \\ B \end{matrix}\right] \in B(H)^2_+$, meaning $A,B\geq 0$, and define $$ \left\|\left[\begin{...

In the paper titled "Nonlinear completely positive maps" M. D. Choi and T. Ando extended natural definition of completely positive maps ignoring the linearity condition (Aspects of positivity in ...

Let E be a real symmetric matrix in $M_n(\mathbb{R})$ where $ n=2m$ and $$E=\left(\begin{array}{cc} G & X \\ X^t & H \end{array}\right)$$ where $G,H,X$ are $m\times m$ matrices. Suppose that $...

I am aware of maps that are positive but not completely positive (for example transpose map). BUT I can not think of an example of the following type. Does there exist an operator $T$ such that a map $...