Expand all Collapse all  Results 26  50 of 56 
26. CMB 2008 (vol 51 pp. 487)
Laplace Transform Type Multipliers for Hankel Transforms In this paper we establish that Hankel multipliers
of Laplace transform type are bounded from $L^p(w)$ into itself
when $1

27. CMB 2008 (vol 51 pp. 348)
The Reconstruction Property in Banach Spaces and a Perturbation Theorem Perturbation theory is a fundamental tool in Banach space theory.
However, the applications of the classical results
are limited by the fact that they force the
perturbed sequence to be equivalent to the given sequence.
We will develop
a more general perturbation theory that does not force equivalence of the
sequences.
Category:42C15 
28. CMB 2007 (vol 50 pp. 85)
Classification of Finite GroupFrames and SuperFrames Given a finite group $G$, we examine the classification of all
frame representations of $G$ and the classification of all
$G$frames, \emph{i.e.,} frames induced by group representations of $G$.
We show that the exact number of equivalence classes of $G$frames
and the exact number of frame representations can be explicitly
calculated. We also discuss how to calculate the largest number
$L$ such that there exists an $L$tuple of strongly disjoint
$G$frames.
Keywords:frames, groupframes, frame representations, disjoint frames Categories:42C15, 46C05, 47B10 
29. CMB 2006 (vol 49 pp. 414)
Commutators Estimates on TriebelLizorkin Spaces In this paper, we consider the behavior of the commutators of convolution
operators on the TriebelLizorkin spaces $\dot{F}^{s, q} _p$.
Keywords:commutators, TriebelLizorkin spaces, paraproduct Categories:42B, 46F 
30. CMB 2006 (vol 49 pp. 438)
Unimodular Roots of\\ Special Littlewood Polynomials We call $\alpha(z) = a_0 + a_1 z + \dots + a_{n1} z^{n1}$ a Littlewood
polynomial if $a_j = \pm 1$ for all $j$. We call $\alpha(z)$ selfreciprocal
if $\alpha(z) = z^{n1}\alpha(1/z)$, and call $\alpha(z)$ skewsymmetric if
$n = 2m+1$ and $a_{m+j} = (1)^j a_{mj}$ for all $j$. It has been observed
that Littlewood polynomials with particularly high minimum modulus on
the unit
circle in $\bC$ tend to be skewsymmetric. In this paper, we prove that a
skewsymmetric Littlewood polynomial cannot have any zeros on the unit circle,
as well as providing a new proof of the known result that a selfreciprocal
Littlewood polynomial must have a zero on the unit circle.
Categories:26C10, 30C15, 42A05 
31. CMB 2006 (vol 49 pp. 3)
On a Class of Singular Integral Operators With Rough Kernels In this paper, we study the $L^p$ mapping properties of a class of singular
integral operators with rough kernels belonging to certain block spaces. We
prove that our operators are bounded on $L^p$ provided that their kernels
satisfy a size condition much weaker than that for the classical
Calder\'{o}nZygmund singular integral operators. Moreover, we present an
example showing that our size condition is optimal. As a consequence of our
results, we substantially improve a previously known result on certain maximal
functions.
Keywords:Singular integrals, Rough kernels, Square functions,, Maximal functions, Block spaces Categories:42B20, 42B15, 42B25 
32. CMB 2005 (vol 48 pp. 382)
Uniform Estimates of Ultraspherical Polynomials of Large Order In this paper we prove the sharp inequality
$$ P_n^{(s)}(x)\leq
P_n^{(s)}(1)\bigl(x^n +\frac{n1}{2 s+1}(1x^n)\bigr),$$
where
$P_n^{(s)}(x)$ is the classical ultraspherical polynomial of
degree $n$ and order $s\ge n\frac{1+\sqrt 5}{4}$. This inequality
can be refined in $[0,z_n^s]$ and $[z_n^s,1]$, where $z_n^s$
denotes the largest zero of $P_n^{(s)}(x)$.
Categories:42C05, 33C47 
33. CMB 2005 (vol 48 pp. 370)
Trigonometric Multipliers on $H_{2\pi}$ In this paper we consider multipliers on the real Hardy space
$H_{2\pi}$. It is known that the Marcinkiewicz and the
H\"ormanderMihlin conditions are sufficient for the corresponding
trigonometric multiplier to be bounded on $L_{2\pi}^p$, $1

34. CMB 2005 (vol 48 pp. 260)
A Restriction Theorem for a \\$k$Surface in $\mathbb R ^n$ We establish a sharp Fourier restriction estimate
for a measure on a $k$surface in $\mathbb R ^n$, where $n=k(k+3)/2$.
Keywords:Fourier restriction Category:42B10 
35. CMB 2004 (vol 47 pp. 475)
Uniqueness of Almost Everywhere Convergent Vilenkin Series D. J. Grubb [3] has shown that uniqueness holds, under a
mild growth condition, for Vilenkin series which converge almost
everywhere to zero. We show that, under even less restrictive
growth conditions, one can replace the limit function 0 by an
arbitrary $f\in L^q$, when $q>1$.
Categories:43A75, 42C10 
36. CMB 2004 (vol 47 pp. 3)
Singular Integrals With Rough Kernels In this paper we establish the $L^p$ boundedness of a class of
singular integrals with rough kernels associated to polynomial
mappings.
Category:42B20 
37. CMB 2003 (vol 46 pp. 191)
Weak Type Estimates of the Maximal Quasiradial BochnerRiesz Operator On Certain Hardy Spaces Let $\{A_t\}_{t>0}$ be the dilation group in $\mathbb{R}^n$ generated
by the infinitesimal generator $M$ where $A_t=\exp(M\log t)$, and let
$\varrho\in C^{\infty}(\mathbb{R}^n\setminus\{0\})$ be a
$A_t$homogeneous distance function defined on $\mathbb{R}^n$. For
$f\in \mathfrak{S}(\mathbb{R}^n)$, we define the maximal quasiradial
BochnerRiesz operator $\mathfrak{M}^{\delta}_{\varrho}$ of index
$\delta>0$ by
$$
\mathfrak{M}^{\delta}_{\varrho} f(x)=\sup_{t>0}\mathcal{F}^{1}
[(1\varrho/t)_+^{\delta}\hat f ](x).
$$
If $A_t=t I$ and $\{\xi\in \mathbb{R}^n\mid \varrho(\xi)=1\}$ is a
smooth convex hypersurface of finite type, then we prove in an
extremely easy way that $\mathfrak{M}^{\delta}_{\varrho}$ is well
defined on $H^p(\mathbb{R}^n)$ when $\delta=n(1/p1/2)1/2$ and
$0 n(1/p1/2)1/2$ and $0

38. CMB 2002 (vol 45 pp. 25)
Extrapolation of $L^p$ Data from a Modular Inequality If an operator $T$ satisfies a modular inequality on a rearrangement
invariant space $L^\rho (\Omega,\mu)$, and if $p$ is strictly between
the indices of the space, then the Lebesgue inequality $\int Tf^p
\leq C \int f^p$ holds. This extrapolation result is a partial
converse to the usual interpolation results. A modular inequality for
Orlicz spaces takes the form $\int \Phi (Tf) \leq \int \Phi (C
f)$, and here, one can extrapolate to the (finite) indices $i(\Phi)$
and $I(\Phi)$ as well.
Category:42B25 
39. CMB 2002 (vol 45 pp. 46)
Local $\VMO$ and Weak Convergence in $\hone$ A local version of $\VMO$ is defined, and the local Hardy space
$\hone$ is shown to be its dual. An application to weak$*$
convergence in $\hone$ is proved.
Categories:42B30, 46E99 
40. CMB 2001 (vol 44 pp. 121)
A Necessary Condition for Multipliers of Weak Type $(1,1)$ Simple necessary conditions for weak type $(1,1)$ of
invariant operators on $L(\rr^d)$ and their applications to
rational Fourier multiplier are given.
Categories:42B15, 42B20 
41. CMB 2000 (vol 43 pp. 355)
A DimensionFree WeakType Estimate for Operators on UMDValued Functions Let $\T$ denote the unit circle in the complex plane, and let $X$ be a
Banach space that satisfies\break Burkholder's UMD condition. Fix a natural
number, $N \in \N$. Let $\od$ denote the reverse lexicographical order
on $\Z^N$. For each $f \in L^1 (\T^N,X)$, there exists a strongly
measurable function $\wt{f}$ such that formally, for all $\bfn \in
\Z^N$, $\Dual{{\wt{f}}} (\bfn) = i \sgn_\od (\bfn)
\Dual{f} (\bfn)$. In this paper, we present a summation method for
this conjugate function directly analogous to the martingale methods
developed by Asmar and MontgomerySmith for scalarvalued functions.
Using a stochastic integral representation and an application of
Garling's characterization of UMD spaces, we prove that the associated
maximal operator satisfies a weaktype $(1,1)$ inequality with a
constant independent of the dimension~$N$.
Category:42A61 
42. CMB 2000 (vol 43 pp. 330)
Maximal Operators and Cantor Sets We consider maximal operators in the plane, defined by Cantor sets of
directions, and show such operators are not bounded on $L^2$ if the
Cantor set has positive Hausdorff dimension.
Keywords:maximal functions, Cantor set, lacunary set Categories:42B25, 43A46 
43. CMB 2000 (vol 43 pp. 63)
Sharpness Results and Knapp's Homogeneity Argument We prove that the $L^2$ restriction theorem, and $L^p \to L^{p'}$,
$\frac{1}{p}+\frac{1}{p'}=1$, boundedness of the surface averages
imply certain geometric restrictions on the underlying
hypersurface. We deduce that these bounds imply that a certain
number of principal curvatures do not vanish.
Category:42B99 
44. CMB 2000 (vol 43 pp. 17)
Multilinear Proofs for Convolution Estimates for Degenerate Plane Curves Suppose that $\g \in C^2\bigl([0,\infty)\bigr)$ is a realvalued function
such that $\g(0)=\g'(0)=0$, and $\g''(t)\approx t^{m2}$, for some integer
$m\geq 2$. Let $\Gamma (t)=\bigl(t,\g(t)\bigr)$, $t>0$, be a curve in the
plane, and let $d \lambda =dt$ be a measure on this curve. For a
function $f$
on $\bR^2$, let
$$
Tf(x)=(\lambda *f)(x)=\int_0^{\infty} f\bigl(x\Gamma(t)\bigr)\,dt,
\quad x\in\bR^2 .
$$
An elementary proof is given for the optimal $L^p$$L^q$ mapping
properties of $T$.
Categories:42A85, 42B15 
45. CMB 1999 (vol 42 pp. 463)
A Generalized Characterization of Commutators of Parabolic Singular Integrals Let $x=(x_1, \dots, x_n)\in\rz$ and $\dz_\lz x=(\lz^{\az_1}x_1,
\dots,\lz^{\az_n}x_n)$, where $\lz>0$ and $1\le \az_1\le\cdots
\le\az_n$. Denote $\az=\az_1+\cdots+\az_n$. We characterize those
functions $A(x)$ for which the parabolic Calder\'on commutator
$$
T_{A}f(x)\equiv \pv \int_{\mathbb{R}^n}
K(xy)[A(x)A(y)]f(y)\,dy
$$
is bounded on $L^2(\mathbb{R}^n)$, where $K(\dz_\lz x)=\lz^{\az1}K(x)$,
$K$ is smooth away from the origin and satisfies a certain cancellation
property.
Keywords:parabolic singular integral, commutator, parabolic $\BMO$ sobolev space, homogeneous space, T1theorem, symbol Category:42B20 
46. CMB 1999 (vol 42 pp. 344)
Positive Definite Distributions and Subspaces of $L_p$ With Applications to Stable Processes We define embedding of an $n$dimensional normed space into
$L_{p}$, $0

47. CMB 1999 (vol 42 pp. 198)
Commutators and Analytic Dependence of FourierBessel Series on $(0,\infty)$ In this paper we study the boundedness of the commutators $[b,
S_n]$ where $b$ is a $\BMO$ function and $S_n$ denotes the $n$th
partial sum of the FourierBessel series on $(0,\infty)$.
Perturbing the measure by $\exp(2b)$ we obtain that certain
operators related to $S_n$ depend analytically on the functional
parameter $b$.
Keywords:FourierBessel series, commutators, BMO, $A_p$ weights Category:42C10 
48. CMB 1999 (vol 42 pp. 37)
Operators with Closed Range, PseudoInverses, and Perturbation of Frames for a Subspace Recent work of Ding and Huang shows that if we perturb a bounded
operator (between Hilbert spaces) which has closed range, then the
perturbed operator again has closed range. We extend this result by
introducing a weaker perturbation condition, and our result is then
used to prove a theorem about the stability of frames for a subspace.
Category:42C15 
49. CMB 1998 (vol 41 pp. 398)
Bandlimited wavelets with subexponential decay It is well known that the compactly supported wavelets cannot belong to
the class $C^\infty({\bf R})\cap L^2({\bf R})$. This is also true for
wavelets with exponential decay. We show that one can construct
wavelets in the class $C^\infty({\bf R})\cap L^2({\bf R})$ that are
``almost'' of exponential decay and, moreover, they are
bandlimited. We do this by showing that we can adapt the
construction of the Lemari\'eMeyer wavelets \cite{LM} that
is found in \cite{BSW} so that we obtain bandlimited,
$C^\infty$wavelets on $\bf R$ that have subexponential decay,
that is, for every $0<\varepsilon<1$, there exits $C_\varepsilon>0$
such that $\psi(x)\leq C_\varepsilon e^{x^{1\varepsilon}}$,
$x\in\bf R$. Moreover, all of its derivatives have also
subexponential decay. The proof is constructive and uses the
Gevrey classes of functions.
Keywords:Wavelet, Gevrey classes, subexponential decay Category:42C15 
50. CMB 1998 (vol 41 pp. 478)
Convolution with measures on curves in $\bbd R^3$ We study convolution properties of measures on the curves
$(t^{a_1}, t^{a_2}, t^{a_3})$ in $\hbox{\Bbbvii R}^3$.
Categories:42B15, 42B20 