Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Positive Herz-Schur multipliers and approximation properties of crossed
  products   For a $C^*$-algebra $A$ and a set $X$ we give a Stinespring-type
characterisation of the completely positive Schur $A$-multipliers on
$K(\ell^2(X))\otimes A$. We then relate them to completely positive Herz-Schur
multipliers on $C^*$-algebraic crossed products of the form
$A\rtimes_{\alpha,r} G$, with $G$ a discrete group, whose various versions were
considered earlier by Anantharaman-Delaroche, B\'edos and Conti, and Dong and
Ruan. The latter maps are shown to implement approximation properties, such as
nuclearity or the Haagerup property, for $A\rtimes_{\alpha,r} G$.

29
The categories of this paper are: funct-an
15
The categories of this paper are: nucl-ex
6
The categories of this paper are: astro-ph
28
The categories of this paper are: alg-geom
1
The categories of this paper are: cs
8
The categories of this paper are: hep-ex
26
The categories of this paper are: bayes-an
32
The categories of this paper are: atom-ph
4
The categories of this paper are: cond-mat
11
The categories of this paper are: hep-lat
30
The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th
35
The categories of this paper are: mtrl-th
20
The categories of this paper are: acc-phys
23
The categories of this paper are: solv-int
37
The categories of this paper are: supr-con