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On a counterexample to a conjecture by blackadar

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posted on 2024-11-15, 08:03 authored by Adam Sorensen
Blackadar conjectured that if we have a split short-exact sequence 0-I-A-C-0 were I is semiprojective then A must be semiprojective. Eilers and Katsura have found a counterexample to this conjecture. Presumably Blackadar asked that the extension be split to make it more likely that semiprojectivity of I would imply semiprojectivity of A. But oddly enough, in all the counterexamples of Eilers and Katsura the quotient map from A to A/I=~C is split. We will show how to modify their examples to find a non-semiprojective C* -algebra B with a semiprojective idal J such that B/J is the complex numbers and the quotient map does not split.

History

Citation

Sorensen, A. P. W. (2013). On a counterexample to a conjecture by blackadar. Springer Proceedings in Mathematics & Statistics, 58 295-303.

Volume

58

Pagination

295-303

Language

English

RIS ID

88033

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