Opuscula Math. 31, no. 3 (2011), 303-315
http://dx.doi.org/10.7494/OpMath.2011.31.3.303

Opuscula Mathematica

# Investigating the numerical range and q-numerical range of non square matrices

Aikaterini Aretaki
John Maroulas

Abstract. A presentation of numerical ranges for rectangular matrices is undertaken in this paper, introducing two different definitions and elaborating basic properties. Further, we extend to the $$q$$-numerical range.

Keywords: numerical range, projectors, matrix norms, singular values.

Mathematics Subject Classification: 15A60, 15A18, 47A12, 47A30.

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• Aikaterini Aretaki
• National Technical University of Athens, Department of Mathematics, Zografou Campus, 15780 Athens, Greece
• John Maroulas
• National Technical University of Athens, Department of Mathematics, Zografou Campus, 15780 Athens, Greece
• Revised: 2010-10-18.
• Accepted: 2010-10-18.