Let us suppose we have a diagonalisable $5 \times 5$ matrix $A$. What is the meaning of $|A|$?
I am a student of fluid dynamics. I am referring to the Blazek's Computational Fluid Dynamics: Principles and applications (2nd edition). I am referring to Roe flux discretization, where $A$ is a Roe matrix, and in the flux equation, we have $|A|$.
Surely, it would be useful to know this concept in detail.