منابع مشابه
S - Numbers of Elementary Operators on C ∗ - Algebras
We study the s-numbers of elementary operators acting on C∗algebras. The main results are the following: If τ is any tensor norm andA,B ∈ B(H) are such that the sequences s(A), s(B) of their singular numbers belong to a stable Calkin space i then the sequence of approximation numbers ofA⊗τB belongs to i. If A is a C∗-algebra, i is a stable Calkin space, s is an s-number function, and ai, bi ∈ A...
متن کاملA note on positivity of elementary operators
We show that operators on n×n matrices which are representable in the form T (X) = ∑` i=1 aiXbi (for ai and bi n×n matrices) and are k-positive for k = [ √ `] must be completely positive. As a consequence, elementary operators on a C*-algebra with minimal length ` which are k-positive for k = [ √ `] must be completely positive. For A a C*-algebra, an operator T :A→ A is called an elementary ope...
متن کاملComputing the Norms of Elementary Operators
We provide a direct proof that the Haagerup estimate on the completely bounded norm of elementary operators is best possible in the case of B(H) via a generalisation of a theorem of Stampfli. We show that for an elementary operator T of length `, the completely bounded norm is equal to the k-norm for k = `. A C*-algebra A has the property that the completely bounded norm of every elementary ope...
متن کاملUniform Approximation by Elementary Operators
On a separable C-algebra A every (completely) bounded map which preserves closed two sided ideals can be approximated uniformly by elementary operators if and only if A is a finite direct sum of C-algebras of continuous sections vanishing at ∞ of locally trivial C-bundles of finite type.
متن کاملOn genuine Lupac{s}-Beta operators and modulus of continuity
In the present article we discuss approximation properties of genuine Lupac{s}-Beta operators of integral type. We establish quantitative asymptotic formulae and a direct estimate in terms of Ditzian-Totik modulus of continuity. Finally we mention results on the weighted modulus of continuity for the genuine operators.
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: Linear Algebra and its Applications
سال: 2016
ISSN: 0024-3795
DOI: 10.1016/j.laa.2016.06.009