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K-theory — 4 results found.

      
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Uniqueness of the Index Map in Banach Algebra K-theory, II
C. R. Math. Rep. Acad. Sci. Canada Vol. 40 (3) 2018, pp. 91-100
George A. Elliott (Received: 2018/09/01, Revised: 2018/09/01)

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It is shown that the index map in the theory of real Banach algebras is unique as a natural transformation, up to an integral multiple, and modulo a (unique) two-torsion “ghost” map arising from the order-two K\(_1\)-group of the Banach algebra \({\mathbb R}\) (of real numbers). (In the earlier paper this was shown for complex Banach algebras, of course without the “ghost” map, but in way—using Bott periodicity to pass to the opposite parity—that is not available for real Banach algebras. The present approach yields a new proof in the complex case.)

On démontre que l’application index dans la K-théorie des algèbres de Banach réelles (ou complexes) est essentiellment unique.

Uniqueness of the Index Map in Banach Algebra K-Theory
C. R. Math. Rep. Acad. Sci. Canada Vol. 36 (2-3) 2014, pp. 93–96
George A. Elliott (Received: 2014/06/18)

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It is shown that the index map in Banach algebra K-theory, as a natural map from the K\(_1\)-group of a quotient of a Banach algebra to the K\(_0\)-group of the corresponding ideal, is unique (up to an integral multiple).

Il est démontré que l’application index dans la K-théorie des algèbres de Banach est unique, dans un sens très naturel.

Torsion in the ${K_0}$-Group of a Recursive Subhomogeneous Algebra
C. R. Math. Rep. Acad. Sci. Canada Vol. 31 (4) 2009, pp. 107–114
Sandro Molina-Cabrera (Received: 2009/07/20)

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We show that the \(K_0\)-group of an inductive limit of recursive subhomogeneous algebras with compact metrizable spaces of dimension at most one as local spectra is torsion free. This result implies that the \(K_0\)-group of a unital simple AH algebra which is the inductive limit of recursive subhomogeneous algebras, with compact metrizable spaces of dimension at most one as local spectra, is torsion free. This proves that Li’s reduction theorem for the dimension of the local spectra of unital simple AH algebras cannot be improved, in other words, that the dimension of the local spectra of unital simple AH algebras cannot be further reduced from two to one, even when we use subhomogeneous algebras. This also shows that if a reduction theorem for the dimension of the local spectra of simple inductive limits of recursive subhomogeneous algebras exists, then, after the reduction, the local spectra of the building blocks cannot always be one dimensional.

Nous démontrons que le \(K_0\)-groupe d’une limite inductive des algèbres sous-homogènes récursives, dont les spectres locaux consistent en des espaces compacts métrisables de dimension au plus un, n’a pas de torsion. Ce résultat implique que les \(K_0\)-groupes d’une algèbre AH simple et avec l’unité qui est la limite des algèbres sous-homogènes rećursives, dont les spectres locaux consistent en des espaces compacts métrisables de dimension au plus un, n’a pas de torsion. Cela prouve que le théorème de Li de la réduction pour la dimension des spectres locaux des algèbres AH simples et avec l’unité ne peut pas être améliorée, en d’autres termes, que la dimension des spectres locaux des algèbres AH simples et avec l’unité ne peut pas encore être réduit de deux à un, même quand on utilise des algèbres sous-homogènes. Cela montre aussi que si un théorème de réduction pour la dimension des spectres locaux d’une limite inductive simple des algèbres sous-homogènes récursives existe, alors, après la réduction, les spectres locaux des blocs de construction ne peuvent pas être toujours de dimension un.

On the irrational quartic algebra
C. R. Math. Rep. Acad. Sci. Canada Vol. 21 (3) 1999, pp. 91–96
S.G. Walters (Received: 1998/10/22)

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algebraic number theory approximation property automorphisms Bessel functions Boson-fermion correspondence C*-algebra Carmichael number center problem Chebyshev transform Classification of simple C*-algebras composition operators continued fractions Cuntz Semigroup cycles of ideals elliptic curves fixed point Fourier transform function fields. general relativity generic property ideals indefinite inner product inductive limits of sub-homogeneous C*- algebras Irrational rotation algebra J-Hermitian matrix K-theory Kahler manifolds L-functions maximal ideal space nonexpansive mapping noninterlacing numerical range orthogonal polynomials Predual space prime number property SP quadratic forms Renormalization rotation algebras Salem number semi-reciprocal polynomials tracially approximate splitting interval algebras unbounded traces Weak Markov set Whitney problems

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