Right half-plane

In

is strictly positive, that is, the set ${\textstyle \{z\in \mathbb {C} \,:\,{\mbox{Re}}(z)>0\}}$.

References

• Rudin, W., Real and Complex Analysis, 3 ed. (McGraw-Hill, 1986).
• Ahlfors, L., Complex Analysis, 3 ed. (McGraw-Hill, 1979).
• Kato, T., Perturbation theory for linear operators, 2 ed. (Springer-Verlag, 1995)