A class of Toeplitz type operators acting on the weighted Bergman spaces of the unit ball in the $n$-dimensional complex space is considered and two pluriharmonic symbols of commuting Toeplitz type operators are completely characterized.

In this note we further our investigation of Baer invariants of groups by obtaining, as consequences of an exact sequence of A. S.-T. Lue, some numerical inequalities for their orders, exponents, and generating sets. An interesting group theoretic corollary is an explicit bound for $|{{\gamma }_{c+1}}\,(G)|$ given that $G\,/\,{{Z}_{c}}\,(G)$ is a finite $p$-group with prescribed order and number of generators.

If $A$ is a subring of a commutative ring $B$ and if $n$ is a positive integer, a number of sufficient conditions are given for “$A[[X]]$ is $n$-root closed in $B[[X]]$” to be equivalent to “$A$ is $n$-root closed in $B$.” In addition, it is shown that if $S$ is a multiplicative submonoid of the positive integers $\mathbb{P}$ which is generated by primes, then there exists a one-dimensional quasilocal integral domain $A$ (resp., a von Neumann regular ring $A$) such that $S=\{n\in \mathbb{P}|A\,\,\text{is}\,n-\text{root}\,\text{closed}\}$ (resp., $S=\{n\in \mathbb{P}\,|\,\,A[[X]]\,\,\text{is}\,n-\text{root}\,\text{closed}\}$).

We prove a topological restriction on the support of Sobolev functions.

Kitada and then Onneweer and Quek have investigated multiplier operators on Hardy spaces over locally compact Vilenkin groups. In this note, we provide an improvement to their results for the Hardy space ${{H}^{1}}$ and provide examples showing that our result applies to a significantly larger group of multipliers.

In a paper [1], published in 1990, in a (somewhat inaccessible) conference proceedings, the authors had shown that for the unitary operators on a separable Hilbert space, endowed with the strong operator topology, those with singular, continuous, simple spectrum, with full support, forma dense ${{G}_{\delta }}$. A similar theorem for bounded self-adjoint operators with a given normbound (omitting simplicity) was recently given by Barry Simon [2], [3], with a totally different proof. In this note we show that a slight modification of our argument, combined with the Cayley transform, gives a proof of Simon’s result, with simplicity of the spectrum added.

It is shown that simple rings over which proper cyclic right modules are continuous coincide with simple right PCI-rings, introduced by Faith.

The two theorems proved yield simple yet reasonably general conditions for triangular matrices to be bounded operators on ${{l}_{p}}$. The theorems are applied to Nörlund and weighted mean matrices.

A new class of homology groups associated to a 3-manifold is defined. The theories measure the syzygies between skein relations in a skein module. We investigate some of the properties of the homology theory associated to the Kauffman bracket.

Garrison [3], Forman [2], and Abel and Siebert [1] showed that for all positive integers $k$ and $N$, there exists a positive integer $\lambda $ such that ${{n}^{k}}\,+\,\lambda $ is prime for at least $N$ positive integers $n$. In other words, there exists $\lambda $ such that ${{n}^{k}}\,+\,\lambda $, represents at least $N$ primes.

We give a quantitative version of this result.We show that there exists $\lambda \le {{x}^{k}}$ such that ${{n}^{k}}\,+\,\lambda $, 1 ≤ n ≤ x, represents at least $\left( \frac{1}{k}\,+\,o\left( 1 \right) \right)\,\pi \left( x \right)$ primes, as $x\to \infty $. We also give some related results.

Let $(X,L)$ be a polarized manifold over the complex number field with dim$X=n$. In this paper, we consider a conjecture of M. C. Beltrametti and A. J. Sommese and we obtain that this conjecture is true if $n=3$ and ${{h}^{0}}\,(L)\,\ge \,2$, or $\dim\,\text{Bs}|L|\le 0$ for any $n\ge 3$. Moreover we can generalize the result of Sommese.

It is well known that the compactly supported wavelets cannot belong to the class ${{C}^{\infty }}\,(\text{R})\,\cap \,{{L}^{2}}\,(R)$. This is also true for wavelets with exponential decay. We show that one can construct wavelets in the class ${{C}^{\infty }}\,(\text{R})\,\cap \,{{L}^{2}}\,(R)$ that are “almost” of exponential decay and, moreover, they are band-limited. We do this by showing that we can adapt the construction of the Lemarié-Meyer wavelets $[\text{LM }\!\!]\!\!\text{ }$ that is found in $[\text{BSW}]$ so that we obtain band-limited, ${{C}^{\infty }}$-wavelets on $R$ that have subexponential decay, that is, for every $0<\varepsilon <1$, there exits ${{C}_{\in }}\,>\,0$ such that $|\psi (x)|\le {{C}_{\varepsilon }}{{e}^{-|x{{|}^{1-\varepsilon }}}}$, $x\in \text{R}$. Moreover, all of its derivatives have also subexponential decay. The proof is constructive and uses the Gevrey classes of functions.

It is shown that if a Banach space $X$ admits a ${{C}^{k}}$-smooth bump function, and ${{X}^{*}}$ is Asplund, then $X$ admits ${{C}^{k}}$-smooth partitions of unity.

Let $b(t)$ be an ${{L}^{\infty }}$ function on $\mathbf{R}$, $\Omega ({y}')$ be an ${{H}^{1}}$ function on the unit sphere satisfying the mean zero property (1) and ${{Q}_{m}}(t)$ be a real polynomial on $\mathbf{R}$ of degree $m$ satisfying ${{Q}_{m}}(0)\,=\,0$. We prove that the singular integral operator

$${{T}_{Qm,}}b\left( f \right)\left( x \right)=p.v.\int\limits_{\mathbf{R}}^{n}{b\left( \left| y \right| \right)}\Omega \left( y \right){{\left| y \right|}^{-n}}f\left( x-{{Q}_{m}}\left( \left| y \right| \right){y}' \right)\,\,dy$$

is bounded in ${{L}^{p}}({{\mathbf{R}}^{n}})$ for $1<p<\infty $, and the bound is independent of the coefficients of ${{Q}_{m}}(t)$.

Let $G$ be a finite group, $H$ a copy of its $p$-Sylow subgroup, and $K{{\left( n \right)}^{*}}\left( - \right)$ the $n$-th Morava $K$-theory at $p$. In this paper we prove that the existence of an isomorphism between $K{{(n)}^{*}}(BG)$ and $K{{(n)}^{*}}(BH)$ is a sufficient condition for $G$ to be $p$-nilpotent.

As a consequence of results due to Bourgain and Stegall, on a separable Banach space whose unit ball is not dentable, the set of norm attaining functionals has empty interior (in the norm topology). First we show that any Banach space can be renormed to fail this property. Then, our main positive result can be stated as follows: if a separable Banach space $X$ is very smooth or its bidual satisfies the ${{\mathcal{w}}^{*}}$-Mazur intersection property, then either $X$ is reflexive or the set of norm attaining functionals has empty interior, hence the same result holds if $X$ has the Mazur intersection property and so, if the norm of $X$ is Fréchet differentiable. However, we prove that smoothness is not a sufficient condition for the same conclusion.

The Gilbert-Pearson characterization of the spectrum is established for a generalized Sturm-Liouville equation with two singular endpoints. It is also shown that strong absolute continuity for the one singular endpoint problem guarantees absolute continuity for the two singular endpoint problem. As a consequence, we obtain the result that strong nonsubordinacy, at one singular endpoint, of a particular solution guarantees the nonexistence of subordinate solutions at both singular endpoints.

We prove that every finite distributive lattice can be represented as the congruence lattice of a finite (planar) semimodular lattice.

A closed convex subset of ${{c}_{0}}$ has the fixed point property (fpp) if every nonexpansive self mapping of it has a fixed point. All nonempty weak compact convex subsets of ${{c}_{0}}$ are known to have the fpp. We show that closed convex subsets with a nonempty interior and nonempty convex subsets which are compact in a topology slightly coarser than the weak topology may fail to have the fpp.

If $F$ and ${F}'$ are free $R$-modules, then $M\cong F/H$ and $M\,\cong \,{F}'\,/\,{H}'$ are viewed as equivalent presentations of the $R$-module $M$ if there is an isomorphism $F\,\to \,{F}'$ which carries the submodule $H$ onto ${H}'$. We study when presentations of modules of projective dimension 1 over Prüfer domains of finite character are necessarily equivalent.