Asymptotics for the Taylor coefficients of certain infinite products

The Ramanujan Journal - Let $$(m_1,\ldots ,m_J)$$ and $$(r_1,\ldots ,r_J)$$ be two sequences of J positive integers satisfying $$1\le r_j< m_j$$ for all $$j=1,\ldots ,J$$ . Let $$(\delta...     

Counter-examples to the Dunford–Schwartz pointwise ergodic theorem on $$\varvec{L^1+L^\infty }$$ L 1 + L ∞

Extending a result by Chilin and Litvinov, we show by construction that given any $$\sigma $$ -finite infinite measure space $$(\Omega ,\mathcal {A}, \mu )$$ and a function $$f\in L^1(\Omega )+L^\infty (\Omega )$$ with $$\mu (\{|f|>\varepsilon \})=\infty $$ for some $$\varepsilon >0$$ , there exists a Dunford–Schwartz operator T over $$(\Omega ,\mathcal {A}, \mu )$$ such that $$\frac{1}{N}\sum _{n=1}^N (T^nf)(x)$$ fails to converge for almost every $$x\in \Omega $$ . In addition, for each operator we construct, the set of functions for which pointwise convergence fails almost everywhere is residual in $$L^1(\Omega )+L^\infty (\Omega )$$ .     

单圈图的最大特征值的上界的改进

Let G（V, E） be a unicyclic graph, Cm be a cycle of length m and Cm G, and ui ∈ V（Cm）. The G - E（Cm） are m trees, denoted by Ti, i = 1, 2,..., m. For i = 1, 2,..., m, let eui be the excentricity of ui in Ti and ec = max{eui ： i = 1, 2 , m}. Let κ = ec＋1. Forj = 1,2,...,k- 1, let δij = max{dv ： dist（v, ui） = j,v ∈ Ti}, δj = max{δij ： i = 1, 2,..., m}, δ0 = max{dui ： ui ∈ V（Cm）}. Then λ1（G）≤max{max 2≤j≤k-2 （√δj-1-1＋√δj-1）,2＋√δ0-2,√δ0-2＋√δ1-1}. If G ≌ Cn, then the equality holds, where λ1 （G） is the largest eigenvalue of the adjacency matrix of G.     

Diophantine inequality by unlike powers of primes

The Ramanujan Journal - Suppose that $$\lambda _1,\ldots ,\lambda _5$$ are nonzero real numbers, not all of the same sign, satisfying that $$\frac{\lambda _1}{\lambda _2}$$ is irrational. Then for...     

Continuity of $$L_{p}$$ Balls and an Application to Input-Output Systems

Mathematical Notes - In this paper, the continuity of the set-valued map $$p\rightarrow B_{\Omega,\mathcal{X},p}(r)$$ , $$p\in (1,+\infty)$$ , is proved where $$B_{\Omega,\mathcal{X},p}(r)$$ is the...     

On k-partitions of multisets with equal sums

The Ramanujan Journal - We study the number of ordered k-partitions of a multiset with equal sums, having elements $$\alpha _1,\ldots ,\alpha _n$$ and multiplicities $$m_1,\ldots ,m_n$$ . Denoting...     

Optimal Extensions for pth Power Factorable Operators

Mediterranean Journal of Mathematics - Let $${X(\mu)}$$ be a function space related to a measure space $${(\Omega,\Sigma,\mu)}$$ with $${\chi_\Omega\in X(\mu)}$$ and let $${T\colon X(\mu)\to E}$$...     

A Snevily-type inequality for multisets

Acta Mathematica Hungarica - Alon [1] proved that if $$p$$ is an odd prime, $$1\le n < p$$ and $$a_1,\ldots,a_n$$ are distinct elements in $$Z_p$$ and $$b_1,\ldots,b_n$$ are arbitrary...     

Menon-type identities with respect to sets of units

The Ramanujan Journal - Let $$n\ge 1$$ and let $$\mathbb {Z}_n^\star $$ be the group of units in the ring of residual classes modulo n, let $$m\ge 0$$ , $$k\ge 0$$ , $$m+k\ge 1$$ , $$u_1,\ldots...     

Linear combination of composition operators on $$H^\infty $$ H ∞ and the Bloch space

Archiv der Mathematik - Let $$\lambda _i (i=1,\ldots ,k)$$ be nonzero complex scalars and $$\varphi _i (i=1,..,k)$$ be analytic self-maps of the unit disk $$\mathbb {D}$$ . We show that the...     

Reverse Brascamp–Lieb inequality and the dual Bollobás–Thomason inequality

Archiv der Mathematik - We prove that if $$f:{\mathbb {R}}^n\rightarrow [0,\infty )$$ is an integrable log-concave function with $$f(0)=1$$ and $$F_1,\ldots ,F_r$$ are linear subspaces of...     

An Endpoint Weak-Type Estimate for Multilinear Calderón–Zygmund Operators

Journal of Fourier Analysis and Applications - The purpose of this article is to provide an alternative proof of the weak-type $$\left( 1,\ldots ,1;\frac{1}{m}\right) $$ estimate for m-multilinear...     

两类广泛递归序列的动力特性

We investigate the dynamics of two extensive classes of recursive sequences:xn+1=c∑ k ∑xn-ioxn-i1…xn-i2j+f(xn-io,xn-i1,…,xn-i2k)j=0(i0,i1,…,i2j)∈A2j/c∑ k ∑xn-ioxn-i1…xn-i2j-1+c+f(xn-io,xn-i1,…,xn-i2k)j=1(i0,i1,…,i2j)∈A2j-1 and xn+1=c∑ k ∑xn-ioxn-i1…xn-i2j-1+c+f(xn-io,xn-i1,…,xn-i2k)j=1(i0,i1,…,i2j)∈A2j-1/c∑ k ∑xn-ioxn-i1…xn-i2j+f(xn-io,xn-i1,…,xn-i2k)j=0(i0,i1,…,i2j)∈A2j We prove that their unique positive equilibrium x = 1 is globally asymptotically stable.And a new access is presented to study the theory of recursive sequences.     

On weighted absolute convergence of multiple Fourier series of a function of $${(p_{1} ,\ldots,p_{N})}$$–$${(\Lambda^1 ,\ldots ,\Lambda^N)}$$(Λ1,…,ΛN)– BV

We obtain a sufficient condition for the weighted β-absolute convergence of the multiple Fourier series

$$\sum_{k_{1} \in\mathbb{Z}} \cdots \sum_{k_{N} \in\mathbb{Z}} \gamma_{k_{1} ,\ldots ,k_{N}} |\hat{f}(k_1 ,\ldots ,k_N)|^\beta,$$

where \({0 < \beta < 2}\) and \({\gamma_{k_{1} ,\ldots ,k_{N}}}\) is a weight sequence, of a function f of the class \({(\Lambda^1 ,\ldots ,\Lambda^N)BV^{(p_{1} ,\ldots ,p_{N})}([0, 2\pi]^N)}\).

     

A short proof for the sum formula and its generalization

For positive integers with a _r  = 2, the multiple zeta value or r-fold Euler sum is defined as [2]

On the average sum of the kth divisor function over values of quadratic polynomials

The Ramanujan Journal - Let $$F(x) \in \mathbb {Z}[x_1 , x_2 ,\ldots , x_n ]$$ , $$n\ge 3$$ , be an n-variable quadratic polynomial with a nonsingular quadratic part. Using the circle method we...     

Freiman Cover Ideals of Unmixed Bipartite Graphs

Mathematical Notes - An equigenerated monomial ideal $$I$$ in the polynomial ring $$R=k[z_1,\ldots, z_n]$$ is a Freiman ideal if $$\mu(I^2)=\ell(I)\mu(I)-{\ell(I)\choose 2}$$ , where $$\ell(I)$$ is...     

一类Kirchhoff型系统解的存在性

In this paper,we are interested in the existence of positive solutions for the Kirchhoff type problems{-(a_1 + b_1M_1(∫_?|▽u|~pdx))△_(_pu) = λf(u,v),in ?,-(a_2 + b_2M_2(∫?|▽v|~qdx))△_(_qv) = λg(u,v),in ?,u = v = 0,on ??,where 1 p,q N,M i:R_0~+→ R~+(i = 1,2) are continuous and increasing functions.λ is a parameter,f,g ∈ C~1((0,∞) ×(0,∞)) × C([0,∞) × [0,∞)) are monotone functions such that f_s,f_t,g_s,g_t ≥ 0,and f(0,0) 0,g(0,0) 0(semipositone).Our proof is based on the sub-and super-solutions techniques.