Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Angles in C*-algebras   In this work we characterise the C*-algebras A generated by projections with
the property that every pair of projections in A has positive angle, as certain
extensions of abelian algebras by algebras of compact operators. We show that
this property is equivalent to a lattice theoretic property of projections and
also to the property that the set of finite-dimensional *-subalgebras of A is
directed.

9
The categories of this paper are: nlin
3
The categories of this paper are: physics
36
The categories of this paper are: cmp-lg
27
The categories of this paper are: comp-gas
14
The categories of this paper are: math-ph
34
The categories of this paper are: chem-ph
37
The categories of this paper are: supr-con
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
4
The categories of this paper are: cond-mat
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The categories of this paper are: chao-dyn
23
The categories of this paper are: solv-int
1
The categories of this paper are: cs
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The categories of this paper are: nucl-th
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The categories of this paper are: econ
26
The categories of this paper are: bayes-an