Root subsystems of rank 2 hyperbolic root systems

Lisa Carbone, Matt Kownacki, Scott H. Murray +1

Let $\Delta$ be a rank 2 hyperbolic root system. Then $\Delta$ has generalized Cartan matrix $H(a,b)=\left(\begin{array}{cc}2& -b\\ -a& 2\end{array}\right)$ indexed by $a,b\in…