Probabilistic and average linear widths of weighted Sobolev spaces on the ball equipped with a Gaussian measure

Let $L_{q,\mu}$, $1\leq q\leq\infty$, denotes the weighted $L_q$ space of functions on the unit ball $\Bbb B^d$ with respect to weight $(1-\|x\|_2^2)^{\mu-\frac12},\,\mu\ge 0$, and let $W_{2,\mu}^r$ be the weighted Sobolev space on $\Bbb B^d$ with a Gaussian measure $\nu$. We investigate the probabilistic linear $(n,\delta)$-widths $\lambda_{n,\delta}(W_{2,\mu}^r,\nu,L_{q,\mu})$ and the $p$-average linear $n$-widths $\lambda_n^{(a)}(W_{2,\mu}^r,\mu,L_{q,\mu})_p$, and obtain their asymptotic orders for all $1\le q\le \infty$ and $0<p<\infty$

Prescribed matchings extend to Hamiltonian cycles in hypercubes with faulty edges

Ruskey and Savage asked the following question: Does every matching of $Q_{n}$ for $n\geq2$ extend to a Hamiltonian cycle of $Q_{n}$? J. Fink showed that the question is true for every perfect matching, and solved the Kreweras' conjecture. In this paper we consider the question in hypercubes with faulty edges. We show that every matching $M$ of at most $2n-1$ edges can be extended to a Hamiltonian cycle of $Q_{n}$ for $n\geq2$. Moreover, we can prove that when $n\geq4$ and $M$ is nonempty this result still holds even if $Q_{n}$ has at most $n-1-\lceil\frac{|M|}{2}\rceil$ faulty edges with one exception.Comment: 16 pages, 10 figure

Bilinear Riesz means on the Heisenberg group

In this article, we investigate the bilinear Riesz means $S^{\alpha }$ associated to the sublaplacian on the Heisenberg group. We prove that the operator $S^{\alpha }$ is bounded from $L^{p_{1}}\times L^{p_{2}}$ into $L^{p}$ for $1\leq p_{1}, p_{2}\leq \infty$ and $1/p=1/p_{1}+1/p_{2}$ when $\alpha$ is large than a suitable smoothness index $\alpha (p_{1},p_{2})$. There are some essential differences between the Euclidean space and the Heisenberg group for studying the bilinear Riesz means problem. We make use of some special techniques to obtain a lower index $\alpha (p_{1},p_{2})$

Wiener measure for Heisenberg group

In this paper, we build Wiener measure for the path space on the Heisenberg group by using of the heat kernel corresponding to the sub-Laplacian and give the definition of the Wiener integral. Then we give the Feynman-Kac formula.Comment: 14 page

Positive Cubature formulas and Marcinkiewicz-Zygmund inequalities on spherical caps

Let $\Pi_n^d$ denote the space of all spherical polynomials of degree at most $n$ on the unit sphere \sph of $\mathbb{R}^{d+1}$, and let $d(x, y)$ denote the usual geodesic distance $\arccos x\cdot y$ between x, y\in \sph. Given a spherical cap B(e,\al)=\{x\in\sph: d(x, e) \leq \al\}, (e\in\sph, \text{$\al\in (0,\pi)$ is bounded away from $\pi$}), we define the metric \rho(x,y):=\frac 1{\al} \sqrt{(d(x, y))^2+\al(\sqrt{\al-d(x, e)}-\sqrt{\al-d(y,e)})^2}, where x, y\in B(e,\al). It is shown that given any \be\ge 1, $1\leq p<\infty$ and any finite subset \Ld of B(e,\al) satisfying the condition \dmin_{\sub{\xi,\eta \in \Ld \xi\neq \eta}} \rho (\xi,\eta) \ge \f \da n with \da\in (0,1], there exists a positive constant $C$, independent of \al, $n$, \Ld and \da, such that, for any $f\in\Pi_{n}^d$, \begin{equation*} \sum_{\og\in \Ld} (\max_{x,y\in B_\rho (\og, \be\da/n)}|f(x)-f(y)|^p) |B_\rho(\og, \da/n)| \le (C \dz)^p \int_{B(e,\al)} |f(x)|^p d\sa(x),\end{equation*} where d\sa(x) denotes the usual Lebesgue measure on \sph, B_\rho(x, r)=\Bl\{y\in B(e,\al): \rho(y,x)\leq r\Br\}, (r>0), and \Bl|B_\rho(x, \f\da n)\Br|=\int_{B_{\rho}(x, \da/n)} d\sa(y) \sim \al ^{d}\Bl[ (\f{\da}n)^{d+1}+ (\f\da n)^{d} \sqrt{1-\f{d(x, e)}\al}\Br]. As a consequence, we establish positive cubature formulas and Marcinkiewicz-Zygmund inequalities on the spherical cap B(e,\al)

The intrinsic square function characterizations of weighted Hardy spaces

In this paper, we will study the boundedness of intrinsic square functions on the weighted Hardy spaces $H^p(w)$ for $0<p<1$, where $w$ is a Muckenhoupt's weight function. We will also give some intrinsic square function characterizations of weighted Hardy spaces $H^p(w)$ for $0<p<1$.Comment: 17 page

Tractability of non-homogeneous tensor product problems in the worst case setting

We study multivariate linear tensor product problems with some special properties in the worst case setting. We consider algorithms that use finitely many continuous linear functionals. We use a unified method to investigate tractability of the above multivariate problems, and obtain necessary and sufficient conditions for strong polynomial tractability, polynomial tractability, quasi-polynomial tractability, uniformly weak tractability, $(s,t)$-weak tractability, and weak tractability. Our results can apply to multivariate approximation problems with kernels corresponding to Euler kernels, Wiener kernels, Korobov kernels, Gaussian kernels, and analytic Korobov kernels.Comment: 23 page

Boundedness of the bilinear Bochner-Riesz Means in the non-Banach triangle case

In this article, we investigate the boundedness of the bilinear Bochner-Riesz means $S^{\alpha }$ in the non-Banach triangle case. We improve the corresponding results in [Bern] in two aspects: Our partition of the non-Banach triangle is simpler and we obtain lower smoothness indices $\alpha (p_{1},p_{2})$ for various cases apart from $1 \leq p_1=p_2 <2$

On filtered polynomial approximation on the sphere

This paper considers filtered polynomial approximations on the unit sphere $\mathbb{S}^d\subset \mathbb{R}^{d+1}$, obtained by truncating smoothly the Fourier series of an integrable function $f$ with the help of a "filter" $h$, which is a real-valued continuous function on $[0,\infty)$ such that $h(t)=1$ for $t\in[0,1]$ and $h(t)=0$ for $t\ge2$. The resulting "filtered polynomial approximation" (a spherical polynomial of degree $2L-1$) is then made fully discrete by approximating the inner product integrals by an $N$-point cubature rule of suitably high polynomial degree of precision, giving an approximation called "filtered hyperinterpolation". In this paper we require that the filter $h$ and all its derivatives up to $\lfloor\tfrac{d-1}{2}\rfloor$ are absolutely continuous, while its right and left derivatives of order $\lfloor \tfrac{d+1}{2}\rfloor$ exist everywhere and are of bounded variation. Under this assumption we show that for a function $f$ in the Sobolev space $W^s_p(\mathbb{S}^d),\ 1\le p\le \infty$, both approximations are of the optimal order $L^{-s}$, in the first case for $s>0$ and in the second fully discrete case for $s>d/p$

Cayley Configuration Spaces of 1-dof Tree-decomposable Linkages, Part II: Combinatorial Characterization of Complexity

We continue to study Cayley configuration spaces of 1-dof linkages in 2D begun in Part I of this paper, i.e. the set of attainable lengths for a non-edge. In Part II, we focus on the algebraic complexity of describing endpoints of the intervals in the set, i.e., the Cayley complexity. Specifically, We focus on Cayley configuration spaces of a natural class of 1-dof linkages, called 1-dof tree-decomposable linkages. The underlying graphs G satisfy the following: for some base non-edge f, G \cup f is quadratic-radically solvable (QRS), meaning that G \cup f is minimally rigid, and given lengths \bar{l} of all edges, the corresponding linkage (G \cup f, \bar{l}) can be simply realized by ruler and compass starting from f. It is clear that the Cayley complexity only depends on the graph G and possibly the non-edge f. Here we ask whether the Cayley complexity depends on the choice of a base non-edge f. We answer this question in the negative, thereby showing that low Cayley complexity is a property of the graph G (independent of the non-edge f). Then, we give a simple characterization of graphs with low Cayley complexity, leading to an efficient algorithmic characterization, i.e. an efficient algorithm for recognizing such graphs. Next, we show a surprising result that (graph) planarity is equivalent to low Cayley complexity for a natural subclass of 1-dof triangle-decomposable graphs. While this is a finite forbidden minor graph characterization of low Cayley complexity, we provide counterexamples showing impossibility of such finite forbidden minor characterizations when the above subclass is enlarged