• Title/Summary/Keyword: C-algebras

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A NOTE ON STAR TOPOLOGICAL ALGEBRAS

  • ANSARI-PIRI, E.
    • Honam Mathematical Journal
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    • v.27 no.1
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    • pp.77-82
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    • 2005
  • $C^*$-algebras which are closed sub-algebras of Banach algebras have been studied many years ago. In this note we extend the main definition of $C^*$-algebras to metrizable topological algebras.

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EXTREMALLY RICH GRAPH $C^*$-ALGEBRAS

  • Jeong, J.A
    • Communications of the Korean Mathematical Society
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    • v.15 no.3
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    • pp.521-531
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    • 2000
  • Graph C*-algebras C*(E) are the universal C*-algebras generated by partial isometries satisfying the Cuntz-Krieger relations determined by directed graphs E, and it is known that a simple graph C*-algebra is extremally rich in sense that it contains enough extreme consider a sufficient condition on a graph for which the associated graph algebra(possibly nonsimple) is extremally rich. We also present examples of nonextremally rich prime graph C*-algebras with finitely many ideals and with real rank zero.

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K-THEORY OF CROSSED PRODUCTS OF C*-ALGEBRAS

  • SUDO TAKAHIRO
    • The Pure and Applied Mathematics
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    • v.12 no.1
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    • pp.1-15
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    • 2005
  • We study continuous fields and K-groups of crossed products of C*-algebras. It is shown under a reasonable assumption that there exist continuous fields of C* -algebras between crossed products of C* -algebras by amenable locally compact groups and tensor products of C* -algebras with their group C* -algebras, and their K-groups are the same under the additional assumptions.

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STABLE RANKS OF MULTIPLIER ALGEBRAS OF C*-ALGEBRAS

  • Sudo, Takahiro
    • Communications of the Korean Mathematical Society
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    • v.17 no.3
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    • pp.475-485
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    • 2002
  • We estimate the stable rank, connected stable rank and general stable rank of the multiplier algebras of $C^{*}$-algebras under some conditions and prove that the ranks of them are infinite. Moreover, we show that for any $\sigma$-unital subhomogeneous $C^{*}$-algebra, its stable rank is equal to that of its multiplier algebra.

The Real Rank of CCR C*-Algebra

  • Sudo, Takahiro
    • Kyungpook Mathematical Journal
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    • v.48 no.2
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    • pp.223-232
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    • 2008
  • We estimate the real rank of CCR C*-algebras under some assumptions. A applications we determine the real rank of the reduced group C*-algebras of non-compac connected, semi-simple and reductive Lie groups and that of the group C*-algebras of connected nilpotent Lie groups.

Spectral subspaces for compact group actions on $C^*$-algebras

  • Jang, Sun-Young
    • Bulletin of the Korean Mathematical Society
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    • v.34 no.4
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    • pp.525-533
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    • 1997
  • We analysis spectral subspaces of $C^*$-algebras for a compacr group action. And we prove the condition that the fixed point algebra of the product action is the tensor product of the fixed point algebras.

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SOME REDUCED FREE PRODUCTS OF ABELIAN C*

  • Heo, Jae-Seong;Kim, Jeong-Hee
    • Bulletin of the Korean Mathematical Society
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    • v.47 no.5
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    • pp.997-1000
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    • 2010
  • We prove that the reduced free product of $k\;{\times}\;k$ matrix algebras over abelian $C^*$-algebras is not the minimal tensor product of reduced free products of $k\;{\times}\;k$ matrix algebras over abelian $C^*$-algebras. It is shown that the reduced group $C^*$-algebra associated with a group having the property T of Kazhdan is not isomorphic to a reduced free product of abelian $C^*$-algebras or the minimal tensor product of such reduced free products. The infinite tensor product of reduced free products of abelian $C^*$-algebras is not isomorphic to the tensor product of a nuclear $C^*$-algebra and a reduced free product of abelian $C^*$-algebra. We discuss the freeness of free product $II_1$-factors and solidity of free product $II_1$-factors weaker than that of Ozawa. We show that the freeness in a free product is related to the existence of Cartan subalgebras in free product $II_1$-factors. Finally, we give a free product factor which is not solid in the weak sense.

STABILITY OF HOMOMORPHISMS IN BANACH MODULES OVER A C*-ALGEBRA ASSOCIATED WITH A GENERALIZED JENSEN TYPE MAPPING AND APPLICATIONS

  • Lee, Jung Rye
    • Korean Journal of Mathematics
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    • v.22 no.1
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    • pp.91-121
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    • 2014
  • Let X and Y be vector spaces. It is shown that a mapping $f:X{\rightarrow}Y$ satisfies the functional equation ${\ddag}$ $$2df(\frac{x_1+{\sum}_{j=2}^{2d}(-1)^jx_j}{2d})-2df(\frac{x_1+{\sum}_{j=2}^{2d}(-1)^{j+1}x_j}{2d})=2\sum_{j=2}^{2d}(-1)^jf(x_j)$$ if and only if the mapping $f:X{\rightarrow}Y$ is additive, and prove the Cauchy-Rassias stability of the functional equation (${\ddag}$) in Banach modules over a unital $C^*$-algebra, and in Poisson Banach modules over a unital Poisson $C^*$-algebra. Let $\mathcal{A}$ and $\mathcal{B}$ be unital $C^*$-algebras, Poisson $C^*$-algebras, Poisson $JC^*$-algebras or Lie $JC^*$-algebras. As an application, we show that every almost homomorphism $h:\mathcal{A}{\rightarrow}\mathcal{B}$ of $\mathcal{A}$ into $\mathcal{B}$ is a homomorphism when $h(d^nuy)=h(d^nu)h(y)$ or $h(d^nu{\circ}y)=h(d^nu){\circ}h(y)$ for all unitaries $u{\in}\mathcal{A}$, all $y{\in}\mathcal{A}$, and n = 0, 1, 2, ${\cdots}$. Moreover, we prove the Cauchy-Rassias stability of homomorphisms in $C^*$-algebras, Poisson $C^*$-algebras, Poisson $JC^*$-algebras or Lie $JC^*$-algebras, and of Lie $JC^*$-algebra derivations in Lie $JC^*$-algebras.

HOMOMORPHISMS BETWEEN C*-ALGEBRAS ASSOCIATED WITH THE TRIF FUNCTIONAL EQUATION AND LINEAR DERIVATIONS ON C*-ALGEBRAS

  • Park, Chun-Gil;Hou, Jin-Chuan
    • Journal of the Korean Mathematical Society
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    • v.41 no.3
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    • pp.461-477
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    • 2004
  • It is shown that every almost linear mapping h : A\longrightarrowB of a unital $C^{*}$ -algebra A to a unital $C^{*}$ -algebra B is a homomorphism under some condition on multiplication, and that every almost linear continuous mapping h : A\longrightarrowB of a unital $C^{*}$ -algebra A of real rank zero to a unital $C^{*}$ -algebra B is a homomorphism under some condition on multiplication. Furthermore, we are going to prove the generalized Hyers-Ulam-Rassias stability of *-homomorphisms between unital $C^{*}$ -algebras, and of C-linear *-derivations on unital $C^{*}$ -algebras./ -algebras.

APPROXIMATE BI-HOMOMORPHISMS AND BI-DERIVATIONS IN C*-TERNARY ALGEBRAS

  • Bae, Jae-Hyeong;Park, Won-Gil
    • Bulletin of the Korean Mathematical Society
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    • v.47 no.1
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    • pp.195-209
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    • 2010
  • In this paper, we prove the generalized Hyers-Ulam stability of bi-homomorphisms in $C^*$-ternary algebras and of bi-derivations on $C^*$-ternary algebras for the following bi-additive functional equation f(x + y, z - w) + f(x - y, z + w) = 2f(x, z) - 2f(y, w). This is applied to investigate bi-isomorphisms between $C^*$-ternary algebras.