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What is the definition of projection used here? I would guess it refers to idempotent elements, but I'm not entirely sure. 69.234.16.148 (talk) 23:12, 12 August 2008 (UTC)[reply]
For C*-algebras, projections are self-adjoint idempotents. For concrete C*-algebras, they correspond to orthogonal projections, which is probably where the name comes from. Minimalrho (talk) 02:54, 1 March 2013 (UTC)[reply]
Yes, the article should be renamed "Projectionless C*-algebra" and include some non-trivial examples, like the first one by Blackadar or the reduced group C*-algebra of a free group. Mct mht (talk) 09:28, 1 March 2013 (UTC)[reply]
