Hypergraph Turan Numbers of Vertex Disjoint Cycles

The Turan number of a k-uniform hypergraph H,denoted by exk(n;H),is the maximum number of edges in any k-uniform hypergraph F on n vertices which does not contain H as a subgraph.Let Cl(k)denote the family of all k-uniform minimal cycles of length l;S(l1,…,lr)denote the family of hypergraphs consisting of unions of r vertex disjoint minimal cycles of lengthl1,…lr,respectively,and Cl(k)denote a k-uniform linear cycle of length l.We determine precisely exk(n;S(l1,…,lr)and exk(n;Cl1(k),…,Cl1(k)for sufficiently large n.Our results extend recent results of Füredi and Jiang who determined the Turan numbers for single k-uniform minimal cycles and linear cycles.     

Uniform Hypergraphs under Certain Intersection Constraints between Hyperedges

A hypergraph H is an(n,m)-hypergraph if it contains n vertices and m hyperedges,where n≥1 and m≥ 0 are two integers.Let k be a positive integer and let L be a set of nonnegative integers.A hyper graph H is k-uniform if all its hyperedges have the same size k,and H is L-intersecting if the number of common vertices of every two hyperedges belongs to L.In this paper,we propose and investigate the problem of estimating the maximum k among all k-uniform L-intersecting(n,m)-hypergraphs for fixed n,m ...     

Turán Number of the Family Consisting of a Blow-up of a Cycle and a Blow-up of a Star

Let F={H₁,...,H_k}(k> 1) be a family of graphs.The Turán number of the family F is the maximum number of edges in an n-vertex {H₁,...,H_k)-free graph,denoted by ex(n,F) or ex(n,{H₁,H₂,...,H_k}).The blow-up of a graph H is the graph obtained from H by replacing each edge in H by a clique of the same size where the new vertices of the cliques are all different.In this paper we determine the Turán number of the family cons...     

Tur´an Problems for Berge-(k, p)-Fan Hypergraph*

Let F be a graph. A hypergraph H is Berge-F if there is a bijection f : E(F) → E(H) such that e ? f(e) for every e ∈ E(F). A hypergraph is Berge-F-free if it does not contain a subhypergraph isomorphic to a Berge-F hypergraph. The authors denote the maximum number of hyperedges in an n-vertex r-uniform Berge-F-free hypergraph by ex_r(n, Berge-F).A (k, p)-fan, denoted by F_k,p, is a graph on k(p ? 1) + 1 vertices consisting of k cliques with p vertices that intersect in exactly one common vertex. In this paper they determine the bounds of ex_r(n, Berge-F) when F is a (k, p)-fan for k ≥ 2, p ≥ 3 and r ≥ 3.     

Singly Covered Minimal Elements of Linked Partitions and Cycles of Permutations

Linked partitions were introduced by Dykema(Dykema K J. Multilinear function series and transforms in free probability theory. Adv. Math., 2005, 208(1):351–407) in the study of the unsymmetrized T-transform in free probability theory.Permutation is one of the most classical combinatorial structures. According to the linear representation of linked partitions, Chen et al.(Chen W Y C, Wu S Y J, Yan C H. Linked partitions and linked cycles. European J. Combin., 2008, 29(6): 1408–1426) de?ned the concept of singly covered minimal elements. Let L(n, k) denote the set of linked partitions of [n] with k singly covered minimal elements and let P(n, k) denote the set of permutations of [n] with k cycles. In this paper, we mainly establish two bijections between L(n, k) and P(n, k). The two bijections from a different perspective show the one-to-one correspondence between the singly covered minimal elements in L(n, k) and the cycles in P(n, k).     

THE EXACT MEROMORPHIC SOLUTIONS OF SOME NONLINEAR DIFFERENTIAL EQUATIONS

We find the exact forms of meromorphic solutions of the nonlinear differential equations ■,n≥ 3,k≥1,where q,Q are nonzero polynomials,Q■ Const.,and p₁,p₂,α₁,α₂ are nonzero constants with α₁≠α₂.Compared with previous results on the equation p(z)f³+q(z)f"=-sinα(z) with polynomial coefficients,our results show that the coefficient of the term f~((k)) perturbed by multiplying an exponential function will affect the structur...     

Diophantine Inequality by Unlike Powers of Primes*

Suppose that λ₁, · · ·, λ₅ are nonzero real numbers, not all of the same sign,satisfying that λ₁/λ₂is irrational. Then for any given real number η and ε > 0, the inequality |λ₁p₁+ λ₂p₂~2+ λ₃p₃~3+ λ₄p₄~4+ λ₅p₅~5+ η| <(■)^-19/756+ε has infinitely many solutions in prime variables p₁, · · ·, p₅. This result co...     

RAMSEY NUMBER OF HYPERGRAPH PATHS

Let H =(V, E) be a k-uniform hypergraph. For 1 ≤ s ≤ k-1, an s-path P~(k,s)_n of length n in H is a sequence of distinct vertices v_1, v_2, ···, v_(s+n(k-s)) such that {v_(1+i(k-s)), ···, v_(s+(i+1)(k-s))} is an edge of H for each 0 ≤ i ≤ n-1.In this paper, we prove that R(P~(3 s,s)_n, P~(3 s,s)_3) =(2 n + 1)s + 1 for n ≥ 3.     

On the α-spectra of Uniform Hypergraphs and Its Associated Graphs

For 0 ≤α 1 and a k-uniform hypergraph H, the tensor A_α(H) associated with H is defined as A_α(H) = αD(H) +(1-α)A(H), where D(H) and A(H) are the diagonal tensor of degrees and the adjacency tensor of H, respectively. The α-spectra of H is the set of all eigenvalues of A_α(H) and the α-spectral radius ρ_α(H) is the largest modulus of the elements in the spectrum of A_α(H). In this paper we define the line graph L(H) of a uniform hypergraph H and prove that ρ_α(H) ≤■ρ_α(L(H)) + 1 + α(Δ-1-δ~*/k), where Δ and δ~* are the maximum degree of H and the minimum degree of L(H), respectively. We also generalize some results on α-spectra of G~(k,s), which is obtained from G by blowing up each vertex into an s-set and each edge into a k-set where 1 ≤ s ≤ k/2.     

BIFURCATIONS OF LIMIT CYCLES FORMING COMPOUND EYES IN THE CUBIC SYSTEM

Let H(n)be the maximal number of limit cycle of planar real polynomial differentialsystem with the degree n and C_m~k denote the nest of k limit cycles enclosing m singular points.By computing detection functions,tne authors study bifurcation and phase diagrams in theclass of a planar cubic disturbed Hamiltonian system.In particular,the following conclusionis reached:The planar cubic system(E_ε)has 11 limit cycles,which form the pattern ofcompound eyes of C_9~1(?)2[C'~ε(?)(2C_1~2)and have the symmetrical structure;so the Hilbertnumber H(3)≥11.     

The Twin Domination Numb er of Strong Pro duct of Digraphs

Let γ*(D) denote the twin domination number of digraph D and let D_1  D_2 denote the strong product of D_1 and D_2. In this paper, we obtain that the twin domination number of strong product of two directed cycles of length at least 2.Furthermore, we give a lower bound of the twin domination number of strong product of two digraphs, and prove that the twin domination number of strong product of the complete digraph and any digraph D equals the twin domination number of D.     

Spectrum and Spectral Singularities of a Quadratic Pencil of a Schr?dinger Operator with Boundary Conditions Dependent on the Eigenparameter

In this paper, we consider the following quadratic pencil of Schr?dinger operators L(λ)generated in L²(R⁺) by the equation ■ with the boundary condition ■ where p(x) and q(x) are complex valued functions and α₀, α₁, β₀, β₁ are complex numbers with α₀β₁-α₁β₀≠0. It is proved that L(λ) has a finite number of eigenvalues and spectral singularities,and each of them is of a finite multiplicity...     

Minimal Representations of Cuntz Algebras

Suppose that O_n(2 ≤ n ≤∞) is a Cuntz algebra. There exists a number 1 ≤ k(π, Ω) ≤∞such that if the cyclic representations(H, π, Ω) and(H, π, Ω) of the Cuntz algebra O_n are unitary equivalent, k(π, Ω) = k(π, Ω). Applying the number, one can define a minimal representation of O_n and give a sufficient condition of the minimality for a representation of O_n. Moreover, the relations between minimal states and minimal representations of Cuntz algebras and the relations between the minimality and the irreducibility of the representation of O_n are investigated, respectively.     

The estimate for mean values on prime numbers relative to \frac{4} {p} = \frac{1} {{n_1 }} + \frac{1} {{n_2 }} + \frac{1} {{n_3 }}

If n is a positive integer,let f （n） denote the number of positive integer solutions （n 1,n 2,n 3） of the Diophantine equation 4/n=1/n₁ + 1/n₂ + 1/n₃.For the prime number p,f （p） can be split into f 1 （p） + f 2 （p）,where f i （p） （i=1,2） counts those solutions with exactly i of denominators n 1,n 2,n 3 divisible by p.In this paper,we shall study the estimate for mean values ∑ p相似文献   

一类非齐次核的Hilbert型级数算子最佳搭配参数的充要条件

选择搭配参数a,b,利用权函数方法,可得核为K(m,n)的级数算子T的不等式:‖T(?)‖₍p,β(a,b))≤M(a,b)‖?‖₍p,α(a,b)),?={a_m}一般地,M(a,b)并不是T:l_p~(α(a,b))→l_p~(β(a,b))的算子范数,针对非齐次核K(m,n)=G(m^λ₁/n^λ₂(λ₁λ₂>0),利用权函数方法讨论算子T的最佳搭配参数a,b的充分必要条件,并在a,b为最佳搭配参数时,得到了T的算子范数表达式.     

有向圈的笛卡尔积有向图的双控制数

Let γ*(D) denote the twin domination number of digraph D and let Cm Cn denote the Cartesian product of C_m and C_n, the directed cycles of length m, n ≥ 2. In this paper, we determine the exact values: γ*(C_2?C_n) = n; γ*(C_3 ?C_n) = n if n ≡ 0(mod 3),otherwise, γ*(C_3?C_n) = n + 1; γ*(C_4?C_n) = n + n/2 if n ≡ 0, 3, 5(mod 8), otherwise,γ*(C_4?C_n) = n + n/2 + 1; γ*(C_5?C_n) = 2n; γ*(C_6?C_n) = 2n if n ≡ 0(mod 3), otherwise,γ*(C_6?C_n) = 2n + 2.     

Rainbow Pancyclicity in a Collection of Graphs Under the Dirac-type Condition

Let G={G_i:i∈ [n]} be a collection of not necessarily distinct n-vertex graphs with the same vertex set V,where G can be seen as an edge-colored(multi)graph and each G_i is the set of edges with color i.A graph F on V is called rainbow if any two edges of F come from different Gis’.We say that G is rainbow pancyclic if there is a rainbow cycle C_l of length l in G for each integer l∈ [3,n].In 2020,Joos and Kim proved a rainbow version of Dirac’s theorem:If δ(G_i...     

On Some Cycles in Wenger Graphs

Let p be a prime,q be a power of p,and let Fq be the field of q elements.For any positive integer n,the Wenger graph Wn(q)is defined as follows:it is a bipartite graph with the vertex partitions being two copies of the(n+1)-dimensional vector space Fq^n+1,and two vertices p=(p(1),…,p(n+1))and l=[l(1),…,l(n+1)]being adjacent if p(i)+l(i)=p(1)l(1)i-1,for all i=2,3,…,n+1.In 2008,Shao,He and Shan showed that for n≥2,Wn(q)contains a cycle of length 2 k where 4≤k≤2 p and k≠5.In this paper we extend their results by showing that(i)for n≥2 and p≥3,Wn(q)contains cycles of length 2k,where 4≤k≤4 p+1 and k≠5;(ii)for q≥5,0相似文献   

On the Monotonicity of (κ; g, h)-graphs

A (k;g)-graph is a k-regular graph with girth g. A (k;g)-cage is a (k;g)-graph with the least possible number of vertices. Let f(k;g) denote the number of vertices in a (k;g)-cage. The girth pair of a graph gives the length of a shortest odd and a shortest even cycle. A fc-regular graph with girth pair (g,h) is called a (k;g,h)-graph. A (k;g,h)-cage is a (k;g,h)-graph with the least possible number of vertices. Let f(k;g,h) denote the number of vertices in a (k;g,h)-cage. In this paper, we prove the following strict inequality f(k;h-1,h)相似文献   

Hamiltonicity of 4-connected graphs

Let σk（G） denote the minimum degree sum of k independent vertices in G and α（G） denote the number of the vertices of a maximum independent set of G. In this paper we prove that if G is a 4-connected graph of order n and σ5（G） 〉 n ＋ 3σ（G） ＋ 11, then G is Hamiltonian.