1 citations · 1 across the 6 of their papers we have counts for
8 papers
On the relation between S-spectrum and right spectrum
LuÍs Carvalho, Cristina Diogo, Sérgio Mendes +1
We use the -linearity of to define , the right spectrum of a right -linear operator in a right quaternionic Hilbert space. We show that $σ(…
A note on the essential numerical range of block diagonal operators
Luís Carvalho, Cristina Diogo, Sérgio Mendes +1
In this note we characterize the essential numerical range of a block diagonal o\-pe\-ra\-tor in terms of the numerical ranges of its components.…
S-spectrum and numerical range of a quaternionic operator
Luís Carvalho, Cristina Diogo, Sérgio Mendes
We study the numerical range of bounded linear operators on quaternionic Hilbert spaces and its relation with the S-spectrum. The class of complex operators on quaternionic Hilbert…
On the convexity of the quaternionic essential numerical range
Luís Carvalho, Cristina Diogo, Sérgio Mendes +1
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 on…
The star-center of the quaternionic numerical range
Luís Carvalho, Cristina Diogo, Sérgio Mendes
In this paper we prove that the quaternionic numerical range is always star-shaped and its star-center is given by the equivalence classes of the star-center of the bild. We determ…
On the convexity and circularity of the numerical range of nilpotent quaternionic matrices
Luís Carvalho, Cristina Diogo, Sérgio Mendes
We provide a sufficient condition for the numerical range of a nilpotent matrix N to be circular in terms of the existence of cycles in an undirected graph associated with N. We pr…