We analyze the numerical range of high-dimensional random matrices, obtaining limit results and corresponding quantitative estimates in the non-limit case. For a large class of random matrices their numerical range is shown to converge to a disc. In particular, numerical range of complex Ginibre matrix almost surely converges to the disk of radius √ 2. Since the spectrum of non-hermitian random...

We show that a bounded linear operator A ∈ B(H) is a multiple of a unitary operator if and only if AZ and ZA always have the same numerical radius or the same numerical range for all (rank one) Z ∈ B(H). More generally, for any bounded linear operators A,B ∈ B(H), we show that AZ and ZB always have the same numerical radius (resp., the same numerical range) for all (rank one) Z ∈ B(H) if and on...

the forced convection heat transfer of turbulent al2o3-water nanofluid flow inside the grooved tubeswith the different aspect ratio of the rectangular grooves is numerically investigated. the governingequations have been solved using finite volume method (fvm) coupled with simple algorithm. it isassumed the heat flux is constant on the grooved walls. the single-phase approach is applied for the...

Suppose that K is a convex polyhedron in the n-dimensional Euclidean space R. Suppose that the extreme points of K are P1, P2, . . . , Pm ( m ≥ n + 1). If P is an arbitrary interior point of K, then there exist vertices Pi1 , Pi2 , . . . , Pin+1 of K and a point Q of R n and a positive number r > 0 for which ||Pik − Q|| = r for 1 ≤ k ≤ n + 1 , ||Pj − Q|| ≤ r for 1 ≤ j ≤ m and P is an interior p...

Abstract. Let T1, . . . , Tn be bounded linear operators on a complex Hilbert space H. Then there are compact operators K1, . . . , Kn ∈ B(H) such that the closure of the joint numerical range of the n-tuple (T1−K1, . . . , Tn−Kn) equals to the joint essential numerical range of (T1, . . . , Tn). This generalizes the corresponding result for n = 1. We also show that if S ∈ B(H) and n ∈ N then t...