Rational tetra-inner functions and the special variety of the tetrablock

Omar M. O. Alsalhi, Zinaida A. Lykova

The set \[ \overline{\mathbb{E}}= \{ x \in {\mathbb{C}}^3: \quad 1-x_1 z - x_2 w + x_3 zw \neq 0 \mbox{ whenever } |z| < 1, |w| < 1 \} \] is called the tetrablock and has intriguin…