Scientific journal paper Q2
On the convexity of the quaternionic essential numerical range
Luís Carvalho (Carvalho, L.); Cristina Diogo (Diogo, C.); Sérgio Mendes (Mendes, S.); Helena Soares (Soares, H.);
Journal Title
Proceedings of the Edinburgh Mathematical Society
Year (definitive publication)
2024
Language
English
Country
United Kingdom
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Abstract
The numerical range in the quaternionic setting is, in general, a non-convex subset of the quaternions. The essential numerical range is a refinement of the numerical range that only keeps the elements that have, in a certain sense, infinite multiplicity. We prove that the essential numerical range of a bounded linear operator on a quaternionic Hilbert space is convex. A quaternionic analogue of Lancaster theorem, relating the closure of the numerical range and its essential numerical range, is also provided.
Acknowledgements
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Keywords
Quaternions,Numerical range,Essential numerical range
  • Mathematics - Natural Sciences
Funding Records
Funding Reference Funding Entity
UIDB/04459/2020 Fundação para a Ciência e a Tecnologia
UIDB/04674/2020 Fundação para a Ciência e a Tecnologia
UIDB/00212/2020 Fundação para a Ciência e a Tecnologia
UIDP/04459/2020 Fundação para a Ciência e a Tecnologia