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4 votes
2 answers
671 views

When does this linear matrix equation have a unique symmetric, positive definite solution?

I encountered the following matrix equation for $A, N, Q \in \mathbb{R}^{n \times n}$ and $A^T=-A$ and $N^T=-N$ $$[X,A]+N^TXN+Q = 0$$ where $Q$ is symmetric, positive definite. My final goal is to ...
5 votes
0 answers
376 views

Non-linear positive map

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 ...
5 votes
0 answers
254 views

A weak Perron-Frobenius property for sets of positive matrices

A popular form of the Perron-Frobenius theorem states the following result: if $A$ is a $d \times d$ real matrix all of whose entries are positive, then the spectral radius of $A$ is a simple ...