1. CMB Online first
 Alaghmandan, Mahmood; Crann, Jason

Character density in central subalgebras of compact quantum groups
We investigate quantum group generalizations
of various density results from Fourier analysis on compact groups.
In particular, we establish the density of characters in the
space of fixed points of the conjugation action on $L^2(\mathbb{G})$, and
use this result to show the weak* density and norm density of
characters in $ZL^\infty(\mathbb{G})$ and $ZC(\mathbb{G})$, respectively. As a corollary,
we partially answer an open question of Woronowicz.
At the level of $L^1(\mathbb{G})$, we show that the center
$\mathcal{Z}(L^1(\mathbb{G}))$
is precisely the closed linear span of the quantum characters
for a large class of compact quantum groups, including arbitrary
compact Kac algebras. In the latter setting, we show, in addition,
that $\mathcal{Z}(L^1(\mathbb{G}))$ is a completely complemented
$\mathcal{Z}(L^1(\mathbb{G}))$submodule
of $L^1(\mathbb{G})$.
Keywords:compact quantum group, irreducible character Categories:43A20, 43A40, 46J40 

2. CMB 2014 (vol 58 pp. 3)
3. CMB 2013 (vol 57 pp. 449)
 Alaghmandan, Mahmood; Choi, Yemon; Samei, Ebrahim

ZLamenability Constants of Finite Groups with Two Character Degrees
We calculate the exact amenability constant of the centre of
$\ell^1(G)$ when $G$ is one of the following classes of finite group:
dihedral; extraspecial; or Frobenius with abelian complement and
kernel. This is done using a formula which applies to all finite
groups with two character degrees. In passing, we answer in the
negative a question raised in work of the third author with Azimifard
and Spronk (J. Funct. Anal. 2009).
Keywords:center of group algebras, characters, character degrees, amenability constant, Frobenius group, extraspecial groups Categories:43A20, 20C15 

4. CMB 2010 (vol 53 pp. 447)
 Choi, Yemon

Injective Convolution Operators on l^{∞}(Γ) are Surjective
Let $\Gamma$ be a discrete group and let $f \in \ell^{1}(\Gamma)$. We observe that if the natural convolution operator $\rho_f: \ell^{\infty}(\Gamma)\to \ell^{\infty}(\Gamma)$ is injective, then $f$ is invertible in $\ell^{1}(\Gamma)$. Our proof simplifies and generalizes calculations in a preprint of Deninger and Schmidt by appealing to the direct finiteness of the algebra $\ell^{1}(\Gamma)$. We give simple examples to show that in general one cannot replace $\ell^{\infty}$ with $\ell^{p}$, $1\leq p< \infty$, nor with $L^{\infty}(G)$ for nondiscrete $G$. Finally, we consider the problem of extending the main result to the case of weighted convolution operators on $\Gamma$, and give some partial results.
Categories:43A20, 46L05, 43A22 

5. CMB 2008 (vol 51 pp. 60)
 Janzen, David

F{\o}lner Nets for Semidirect Products of Amenable Groups
For unimodular semidirect products of locally compact amenable
groups $N$ and $H$, we show that one can always construct a
F{\o}lner net of the form $(A_\alpha \times B_\beta)$ for $G$, where
$(A_\alpha)$ is a strong form of F{\o}lner net for $N$ and
$(B_\beta)$ is any F{\o}lner net for $H$. Applications to the
Heisenberg and Euclidean motion groups are provided.
Categories:22D05, 43A07, 22D15, 43A20 

6. CMB 2007 (vol 50 pp. 56)
 Gourdeau, F.; Pourabbas, A.; White, M. C.

Simplicial Cohomology of Some Semigroup Algebras
In this paper, we investigate the higher simplicial cohomology
groups of the convolution algebra $\ell^1(S)$ for various semigroups
$S$. The classes of semigroups considered are semilattices, Clifford
semigroups, regular Rees semigroups and the additive semigroups of
integers greater than $a$ for some integer $a$. Our results are of
two types: in some cases, we show that some cohomology groups are $0$,
while in some other cases, we show that some cohomology groups are
Banach spaces.
Keywords:simplicial cohomology, semigroup algebra Category:43A20 

7. CMB 2004 (vol 47 pp. 445)
 Pirkovskii, A. Yu.

Biprojectivity and Biflatness for Convolution Algebras of Nuclear Operators
For a locally compact group $G$, the convolution product on
the space $\nN(L^p(G))$ of nuclear operators was defined by Neufang
\cite{Neuf_PhD}. We study homological properties of the convolution algebra
$\nN(L^p(G))$ and relate them to some properties of the group $G$,
such as compactness, finiteness, discreteness, and amenability.
Categories:46M10, 46H25, 43A20, 16E65 

8. CMB 1997 (vol 40 pp. 133)
 Blackmore, T. D.

Derivations from totally ordered semigroup algebras into their duals
For a wellbehaved measure $\mu$, on a locally compact
totally ordered set $X$, with continuous part $\mu_c$, we make
$L^p(X,\mu_c)$
into a commutative Banach bimodule over the totally ordered
semigroup algebra
$L^p(X,\mu)$, in such a way that the natural surjection from the algebra
to the module is a bounded derivation. This gives rise to bounded
derivations from $L^p(X,\mu)$
into its dual module and in particular shows that if $\mu_c$ is not
identically zero then $L^p(X,\mu)$ is not weakly
amenable. We show that all bounded derivations from $L^1(X,\mu)$
into its dual module arise in this way and also describe all bounded
derivations from
$L^p(X,\mu)$ into its dual for $1
Categories:43A20, 46M20 
