Abstract:
The article provides a concise overview of key concepts related to right quaternionic linear operators,
quaternionic Hilbert spaces, and quaternionic Krein spaces. It then delves into the study of the quaternionic
Krein space numerical range of a bounded right linear operator and the relationship between this numerical range
and the $S$-spectrum of the operator. The article concludes by establishing spectral inclusion results based on
the quaternionic Krein space numerical range and presenting the corresponding spectral inclusion theorems. In
addition, we generalize some results to infinite dimensional quaternionic Krein spaces and give
some examples.
