For a bounded linear operator A on a Hilbert space  , let ( ) M A be the smallest possible constant in the inequality ( ) ( ) ( ) p p D A M A R A ≤ . Here, p is a point on the smooth portion of the boundary ( ) W A ∂ of the numerical range of A. ( ) p R A is the radius of curvature of ( ) W A ∂ at this point and ( ) p D A is the distance from p to the spectrum of A. In this paper, we compute t...

Numerical techniques for discretization of velocity space in continuum kinetic calculations are described. An efficient spectral collocation method is developed for the speed coordinate – the radius in velocity space – employing a novel set of non-classical orthogonal polynomials. For problems in which Fokker-Planck collisions are included, a common situation in plasma physics, a procedure is d...

This article is devoted to studying some new numerical radius inequalities for Hilbert space operators. Our analysis enables us improve an earlier bound due Kittaneh. It shown, among other, that if $A\in \mathcal{B}(\mathcal{H})$, then \[ \frac{1}{8}\left( {{\left\| A+{{A}^{*}} \right\|}^{2}}+{{\left\| A-{{A}^{*}} \right\|}^{2}} \right)\le \omega ^{2}\left( A \right) \le \left\| \frac{{{\left| ...

,ABSTRACT. There is a formula (Gelfand’s formula) to find the spectral radius of a linear operator defined on a Banach space. That formula does not apply even in normed spaces which are not complete. In this paper we show a formula to find the spectral radius of any linear and compact operator T defined on a complete topological vector space, locally convex. We also show an easy way to find a n...

If A, B are bounded linear operators on a complex Hilbert space, then we prove that $$\begin{aligned} w(A)\le & {} \frac{1}{2}\left( \Vert A\Vert +\sqrt{r\left( |A||A^*|\right) }\right) ,\\ w(AB \pm BA)\le 2\sqrt{2}\Vert B\Vert \sqrt{ w^2(A)-\frac{c^2(\mathfrak {R}(A))+c^2(\mathfrak {I}(A))}{2} }, \end{aligned}$$ where $$w(\cdot ),\left\| \cdot \right\| $$ , and $$r(\cdot )$$ the numerical radi...

Some power inequalities for the numerical radius based on recent Dragomir extension of Furuta's inequality are established. particular cases also provided. Moreover, we get an improvement H\"older-McCarthy operator in case when $r\geq 1$ and refine generalized involving powers sums products Hilbert space operators.

This paper deals with the study of Birkhoff--James orthogonality a linear operator to subspace operators defined between arbitrary Banach spaces. In case domain space is reflexive and finite dimensional we obtain complete characterization. For spaces, same under some additional conditions. an Hilbert H, also L(H), both respect norm as well numerical radius norm.

we give further results for perron-frobenius theory on the numericalrange of real matrices and some other results generalized from nonnegative matricesto real matrices. we indicate two techniques for establishing the main theorem ofperron and frobenius on the numerical range. in the rst method, we use acorresponding version of wielandt's lemma. the second technique involves graphtheory.