Stefanie Gerke, Andrew McDowell
We prove part of a conjecture by Johansson, Kahn and Vu \cite{JKV} regarding threshold functions for the existence of an $H$-factor in a random graph \gnp. We prove that the conjectured threshold function is correct for any graph $H$ which is not covered by its densest subgraphs. We also demonstrate that the main result of \cite{JKV} generalises to multigraphs, digraphs, and a multipartite model.
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In a rooted tree, we call a vertex {\em balanced} if it is at equal distance from all its descendant leaves. We count balanced vertices in three different tree varieties. For decreasing binary trees, we can prove that the probability that a vertex chosen uniformly at random from the set of all trees of a given size is balanced is monotone decreasing.
Neighborhood Balanced 3-Coloring
该研究围绕邻域3平衡图展开，给出其阶数约束，明确广义Petersen图与Pappus图中的3平衡类型，分析3平衡性质在图构造中的保持情况，提出三次3平衡图的两种刻画并完成小阶数分类。
Given a 3-connected biased graph $Ω$ with a balancing vertex, and with frame matroid $F(Ω)$ nongraphic and 3-connected, we determine all biased graphs $Ω'$ with $F(Ω') = F(Ω)$. As a consequence, we show that if $M$ is a 4-connected nongraphic frame matroid represented by a biased graph $Ω$ having a balancing vertex, then $Ω$ essentially uniquely represents $M$. More precisely, all biased graphs representing $M$ are obtained from $Ω$ by replacing a subset of the edges incident to its unique balancing vertex with unbalanced loops.
A $d$-dimensional simplicial complex is balanced if the underlying graph is $(d+1)$-colorable. We present an implementation of cross-flips, a set of local moves introduced by Izmestiev, Klee and Novik which connect any two PL-homeomorphic balanced combinatorial manifolds. As a result we exhibit a vertex minimal balanced triangulation of the real projective plane, of the dunce hat and of the real projective space, as well as several balanced triangulations of surfaces and 3-manifolds on few vertices. In particular we construct small balanced triangulations of the 3-sphere that are non-shellable…
Quasi Neighborhood Balanced Coloring of Graphs
研究图的准邻域平衡着色，定义了该着色的条件及变体，并证明判定此类着色的存在性是NP难问题。
The vertex-pancyclicity of the simplified shuffle-cube and the vertex-bipancyclicity of the balanced shuffle-cube
本文定义了顶点泛圈与双泛圈图，并证明了$n$维简化洗牌立方体在$n\geqslant 6$时顶点泛圈，$n$维平衡洗牌立方体在$n\geqslant 2$时顶点双泛圈。
Lovász has completely characterised the structure of graphs with no two vertex-disjoint cycles, while Slilaty has given a structural characterisation of graphs with no two vertex-disjoint odd cycles; his result is in fact more general, describing signed graphs with no two vertex-disjoint negative cycles. A biased graph is a graph with a distinguished set of cycles (called balanced) with the property that any theta subgraph does not contain exactly two balanced cycles. In this paper we characterise the structure of biased graphs with no two vertex-disjoint unbalanced cycles, answering a questio…
In this paper we find recurrence relations for the asymptotic probability a vertex is $k$ protected in all Motzkin trees. We use a similar technique to calculate the probabilities for balanced vertices of rank $k$. From this we calculate upper and lower bounds for the probability a vertex is balanced and upper and lower bounds for the expected rank of balanced vertices.
An \emph{equitable $(q, r)$-tree-coloring} of a graph $G$ is a $q$-coloring of $G$ such that the subgraph induced by each color class is a forest of maximum degree at most $r$ and the sizes of any two color classes differ by at most $1.$ Let the \emph{strong equitable vertex $r$-arboricity} of a graph $G,$ denoted by $va^\equiv_r (G)$, be the minimum $p$ such that $G$ has an equitable $(q, r)$-tree-coloring for every $q\geq p.$ The values of $va^\equiv_1 (K_{n,n})$ were investigated by Tao and Lin and Wu, Zhang, and Li where exact values of $va^\equiv_1 (K_{n,n})$ were found in some special ca…
The balanced hypercube $BH_{n}$, a variant of the hypercube, is a novel interconnection network for massive parallel systems. It is known that the balanced hypercube remains Hamiltonian after deleting at most $4n-5$ faulty edges if each vertex is incident with at least two edges in the resulting graph for all $n\geq2$. In this paper, we show that there exists a fault-free Hamiltonian cycle in $BH_{n}$ for $n\ge 2$ with $\left | F \right |\le 5n-7$ if the degree of every vertex in $BH_{n}-F$ is at least two and there exists no $f_{4}$-cycles in $BH_{n}-F$, which improves some known results.
A $p$-caterpillar is a caterpillar such that every non-leaf vertex is adjacent to exactly $p$ leaves. We give a tight minimum degree condition for a graph to have a spanning $p$-caterpillar.
A bihole in a bipartite graph $G$ with partite sets $A$ and $B$ is an independent set $I$ in $G$ with $|I\cap A|=|I\cap B|$. We prove lower bounds on the largest order of biholes in balanced bipartite graphs subject to conditions involving the vertex degrees and the average degree.
Color $2$-switches and neighborhood $λ$-balanced graphs with $k$ colors
本文研究了颜色2切换和k种颜色的λ-平衡图，提出新的图类定义并证明了相关平衡数结果。
The balanced hypercube, $BH_n$, is a variant of hypercube $Q_n$. Zhou et al. [Inform. Sci. 300 (2015) 20-27] proposed an interesting problem that whether there is a fault-free Hamiltonian cycle in $BH_n$ with each vertex incident to at least two fault-free edges. In this paper, we consider this problem and show that each fault-free edge lies on a fault-free Hamiltonian cycle in $BH_n$ after no more than $4n-5$ faulty edges occur if each vertex is incident with at least two fault-free edges for all $n\ge 2$. Our result is optimal with respect to the maximum number of tolerated edge faults.
Given any finite simplicial complex Δ, we show how to construct a new simplicial complex Δ_χ that is balanced and vertex decomposable. Moreover, we show that the h-vector of the simplicial complex Δ_χ is precisely the f-vector, denoted f(Δ), of the original complex Δ. We deduce this result by relating f(Δ) with the graded Betti numbers of the Alexander dual of Δ_χ. Our construction generalizes the "whiskering" construction of Villarreal, and Cook and Nagel. As a corollary of our work, we add a new equivalent statement to a theorem of Björner, Frankl, and Stanley that classifies the f-vectors o…
An equality for balanced digraphs
本文证明平衡有向图中，不含环且每个顶点到指定顶点s有路径的k边子集（称为s-收敛）的数量与s无关，推广了关于生成树形图、无环定向和最大无环子图的结果。
The least balanced graphs and trees
本文研究了图和树的最不平衡性，证明了完全图K4附加路径P_{n-4}和星树S5附加路径P_{n-5}是最不平衡的结构。
$(2k+1)$-Neighborhood Balanced Coloring
本文针对素数 $(2k+1)$ 定义并研究 $(2k+1)$-邻域平衡着色，为常见图族建立结果并给出具有该性质的图族示例。
A graph $X$ is said to be {\it distance--balanced} if for any edge $uv$ of $X$, the number of vertices closer to $u$ than to $v$ is equal to the number of vertices closer to $v$ than to $u$. A graph $X$ is said to be {\it strongly distance--balanced} if for any edge $uv$ of $X$ and any integer $k$, the number of vertices at distance $k$ from $u$ and at distance $k+1$ from $v$ is equal to the number of vertices at distance $k+1$ from $u$ and at distance $k$ from $v$. Obviously, being distance--balanced is metrically a weaker condition than being strongly distance--balanced. In this paper, a con…
A balanced edge-coloring of the complete graph is an edge-coloring such that every vertex is incident to each color the same number of times. In this short note, we present a construction of a balanced edge-coloring with six colors of the complete graph on $n=13^k$ vertices, for every positive integer $k$, with no rainbow $K_4$. This solves a problem by Erdős and Tuza.
Which patterns must a two-colouring of $K_n$ contain if each vertex has at least $\varepsilon n$ red and $\varepsilon n$ blue neighbours? In this paper, we investigate this question and its multicolour variant. For instance, we show that any such graph contains a $t$-blow-up of an \textit{alternating 4-cycle} with $t = Ω(\log n)$.
Let $D = (V, E)$ be a strongly connected and balanced digraph with vertex set $V$ and arc set $E.$ The classical distance $d_{ij}^D$ from $i$ to $j$ in $D$ is the length of a shortest directed path from $i$ to $j$ in $D.$ Let $L$ be the Laplacian matrix of $D$ and $ L^{\dagger} = ( l_{ij}^{\dagger} )$ be the Moore-Penrose inverse of $L.$ The resistance distance from $i$ to $j$ is then defined by $r_{ij}^D := l_{ii}^{\dagger } + l_{jj}^{\dagger } - 2 l_{ij}^{\dagger }.$ Let $\{ D_1, D_2, ...., D_k \}$ be a sequence of strongly connected balanced digraphs with $D_i \cap D_j$ having at most one v…
Given a $k$-vertex graph $H$ and an integer $n$, what are the $n$-vertex graphs with the maximum number of induced copies of $H$? This question is closely related to the inducibility problem introduced by Pippenger and Golumbic in 1975, which asks for the maximum possible fraction of $k$-vertex subsets of an $n$-vertex graph that induce a copy of $H$. Huang, Lee and the first author proved that for a random $k$-vertex graph $H$, almost surely the $n$-vertex graphs maximizing the number of induced copies of $H$ are the balanced iterated blow-ups of $H$. In this paper, we consider the case where…
A rooted tree is balanced if the degree of a vertex depends only on its distance to the root. In this paper we determine the sharp threshold for the appearance of a large family of balanced spanning trees in the random geometric graph $\mathcal{G}(n,r,d)$. In particular, we find the sharp threshold for balanced binary trees. More generally, we show that all sequences of balanced trees with uniformly bounded degrees and height tending to infinity appear above a sharp threshold, and none of these appears below the same value. Our results hold more generally for geometric graphs satisfying a mild…
Perfect matching in 4-partite 4-uniform hypergraphs
研究平衡 4 部 4 图中完美匹配的最小顶点度阈值，通过\(k\)部\(k\)图的归约框架，将完美分数匹配存在性转化为有限维优化问题来求解，确定了相应阈值。
Rankwidth of Graphs with Balanced Separations: Expansion for Dense Graphs
本文证明秩宽不小于$72r$的图存在诱导子图满足最小平衡割秩不小于$r$，建立了秩宽与平衡顶点割定义的良链接度测度的新关联，支撑秩扩张可作为稠密图扩张性衡量指标的结论。
Complete tripartite subgraphs of balanced tripartite graphs with large minimum degree
该研究改进了三部图中保证八面体子图的最小度下界，并在额外度条件下证实了Bollobás等人的猜想。
Vertex-colored Turán theorems with applications in extremal hypergraph problems
本文通过顶点着色图的 Turán 型定理和稳定性方法，证明了 Balogh-Clemen-Lidický 关于 $K_5^3$ 的 $\ell_2$ 范数 Turán 问题的猜想，并确定了所有足够大 $n$ 下无 $K_5^3$ 的 $3$-一致超图的最大团数。
The blow-up of a graph is obtained by replacing every vertex with a finite collection of copies so that the copies of two vertices are adjacent if and only if the originals are. If every vertex is replaced with the same number of copies, then the resulting graph is called a balanced blow-up. We show that any graph which contains the maximum number of induced copies of a sufficiently large balanced blow-up of H is itself essentially a blow-up of H. This gives an asymptotic answer to a question in [BEHJ95].
A thoroughly studied problem in Extremal Graph Theory is to find the best possible density condition in a host graph $G$ for guaranteeing the presence of a particular subgraph $H$ in $G$. One such classical result, due to Bollobás and Thomason, and independently Komlós and Szemerédi, states that average degree $O(k^2)$ guarantees the existence of a $K_k$-subdivision. We study two directions extending this result. On the one hand, Verstraëte conjectured that the quadratic bound $O(k^2)$ would guarantee already two vertex-disjoint isomorphic copies of a $K_k$-subdivision. On the other hand, Thom…
The Full P-vertex Problem and Perfect Matchings for Bipartite Graphs
研究二分图中性质(P)与完美匹配的关系，证明性质(P)等价于完美匹配存在的条件，并应用于多类二分图族。
We prove that a random labeled (unlabeled) tree is balanced. We also prove that random labeled and unlabeled trees are strongly $k$-balanced for any $k\geq 3$.
Consider the balanced Ramsey game, in which a player has r colors and where in each step r random edges of an initially empty graph on n vertices are presented. The player has to immediately assign a different color to each edge and her goal is to avoid creating a monochromatic copy of some fixed graph F for as long as possible. The Achlioptas game is similar, but the player only loses when she creates a copy of F in one distinguished color. We show that there is an infinite family of non-forests F for which the balanced Ramsey game has a different threshold than the Achlioptas game, settling …
Let $D$ be a strongly connected balanced bipartite directed graph of order $2a\geq 10$. Let $x,y$ be distinct vertices in $D$. $\{x,y\}$ dominates a vertex $z$ if $x\rightarrow z$ and $y\rightarrow z$; in this case, we call the pair $\{x,y\}$ dominating. In this paper we prove: {\it If the underlying undirected graph of $D$ is not 2-connected and $max\{d(x), d(y)\}\geq 2a-2$ for every dominating pair of vertices $\{x,y\}$, then $D$ contains a cycle of length $2a-2$ unless $D$ is isomorphic to a certain digraph of order ten which we specify.
Note on near-spanning balanced antidirected trees missing from regular tournaments
本文构造了满足半度条件但无法嵌入高度对称锦标赛的近生成平衡反定向树，给出了Stein猜想在均匀次线性度解释下的反例，并确定了最优目标阶及最小宿主阶。
Closed Neighborhood Balanced k-Coloring of Graphs
本文定义图的闭邻域平衡 k-着色，给出其存在的若干充要条件，分析相关图运算，并证明该图类不能通过禁用子图刻画。
Turán problems for suspension of a balanced tree
本文基于Erdős-Sós猜想，确定了当$n\ge 4(4k)^6$时平衡树悬挂图的Turán数$\ex(n,\widehat{T})$的精确界，刻画了所有极图，并证明了一类分解族不含线性森林的图的Turán数。
Given a graph $G = (V,E)$ with vertex weights $w(v)$ and a desired number of parts $k$, the goal in graph partitioning problems is to partition the vertex set V into parts $V_1,\ldots,V_k$. Metrics for compactness, contiguity, and balance of the parts $V_i$ are frequent objectives, with much existing literature focusing on compactness and balance. Revisiting an old method known as striping, we give the first polynomial-time algorithms with guaranteed contiguity and provable bicriteria approximations for compactness and balance for planar grid graphs. We consider several types of graph partitio…
Balanced colorings of Erdős-Rényi hypergraphs
本文研究了稀疏 $r$-一致 $r$-部 Erdős-Rényi 超图的平衡着色问题，确定了其平衡色数的渐近行为，并将 Feige 和 Kogan 关于二部图的结果推广到了更一般的超图情形。
A decomposition theorem for balanced measures
本文研究连通图上平衡概率测度的结构，证明其可分解为若干“基本”极端平衡测度的凸组合，并给出基本平衡测度数量的本质紧上界。
Planar Turán number for balanced double stars
本文确定了平衡双星中最后一个未解图 $S_{3,3}$ 的平面 Turán 数精确值，从而完全解决了所有平衡双星的平面 Turán 数问题。
An oriented hypergraph is a hypergraph together with an incidence orientation such that each edge-vertex incidence is given a label of $+1$ or $-1$. An oriented hypergraph is called incidence balanced if there exists a bipartition of the vertex set such that every edge intersects one part of the bipartition in positively incident vertices with the edge and other part in negatively incident vertices with the edge. In this paper, we investigate the incidence balance of oriented hypergraphs and induced signed hypergraphs by means of the eigenvalues of associated matrices and tensors, and provide …
A balanced partition is a clustering of a graph into a given number of equal-sized parts. For instance, the Bisection problem asks to remove at most k edges in order to partition the vertices into two equal-sized parts. We prove that Bisection is FPT for the distance to constant cliquewidth if we are given the deletion set. This implies FPT algorithms for some well-studied parameters such as cluster vertex deletion number and feedback vertex set. However, we show that Bisection does not admit polynomial-size kernels for these parameters. For the Vertex Bisection problem, vertices need to be re…
Let $G$ be a graph with vertex set $V(G)$ and edge set $E(G)$, and $f$ be a 0-1 labeling of $E(G)$ so that the absolute difference in the number of edges labeled 1 and 0 is no more than one. Call such a labeling $f$ \emph{edge-friendly}. The \emph{edge-balanced index set} of the graph $G$, $EBI(G)$, is defined as the absolute difference between the number of vertices incident to more edges labeled 1 and the number of vertices incident to more edges labeled 0 over all edge-friendly labelings $f$. In 2009, Lee, Kong, and Wang \cite{LeeKongWang} found the $EBI(K_{l,n})$ for $l=1,2,3,4,5$ as well …
Balanced supersaturation and Turan numbers in random graphs
本文证明了Morris和Saxton关于二分图平衡超饱和性质的猜想在含环二分图的弱假设下成立，并将其应用于得到随机图G(n,p)中二分H的Turan数的计数结果与首个一般上界。
Neighborhood Balanced k-Coloring of Graphs
本文研究图的邻域平衡k-着色，推导其存在的必要/充分条件，讨论可实现该着色的图类，证明该判定问题为NP-完全且该图类无禁子图刻画。
The problem of computing induced subgraphs that satisfy some specified restrictions arises in various applications of graph algorithms and has been well studied. In this paper, we consider the following Balanced Connected Subgraph (shortly, BCS) problem. The input is a graph $G=(V,E)$, with each vertex in the set $V$ having an assigned color, "red" or "blue". We seek a maximum-cardinality subset $V'\subseteq V$ of vertices that is color-balanced (having exactly $|V'|/2$ red nodes and $|V'|/2$ blue nodes), such that the subgraph induced by the vertex set $V'$ in $G$ is connected. We show that t…
In a balanced graph decomposition, every vertex of the host graph appears in the same number of blocks. We propose the use of colored loops as a framework for unifying various other types of local balance conditions in graph decompositions. In the basic case where a single graph with colored loops is used as a block, an existence theory for such decompositions follows as a straightforward generalization of previous work on balanced graph decompositions.
Given a directed graph, an equivalence relation on the graph vertex set is said to be balanced if, for every two vertices in the same equivalence class, the number of directed edges from vertices of each equivalence class directed to each of the two vertices is the same. In this paper we describe the quotient and lift graphs of symmetric directed graphs associated with balanced equivalence relations on the associated vertex sets. In particular, we characterize the quotients and lifts which are also symmetric. We end with an application of these results to gradient and Hamiltonian coupled cell …
Nash-Williams proved that every graph has a well-balanced orientation. A key ingredient in his proof is admissible odd-vertex pairings. We show that for two slightly different definitions of admissible odd-vertex pairings, deciding whether a given odd-vertex pairing is admissible is co-NP-complete. This resolves a question of Frank. We also show that deciding whether a given graph has an orientation that satisfies arbitrary local arc-connectivity requirements is NP-complete.
It is well-known that concentrators are sparse graphs of high connectivity, which play a key role in the construction of switching networks; and any semi-vertex transitive graph is isomorphic to a bi-coset graph. In this paper, we prove that random bi-coset graphs are almost always concentrators, and construct some examples of semi-vertex transitive concentrators.
Consider a simple graph in which a random walk begins at a given vertex. It moves at each step with equal probability to any neighbor of its current vertex, and ends when it has visited every vertex. We call such a random walk a random cover tour. It is well known that cycles and complete graphs have the property that a random cover tour starting at any vertex is equally likely to end at any other vertex. Ronald Graham asked whether there are any other graphs with this property. In 1993, Lászlo Lovász and Peter Winkler showed that cycles and complete graphs are the only undirected graphs with …
Local Distance Antimagic Labeling of Neighborhood Balanced Colored Graphs
本文针对无孤立顶点的图定义局部距离反幻标号及相应色数 χ_ld(G)，并研究邻域平衡着色图的标号问题。
Fractional balanced chromatic number of signed subcubic graphs
针对带符号次立方图的平衡着色问题，本文证明除$(K_4,-)$及其开关等价图外所有此类图存在平衡$(5,3)$着色，且给出该特殊图的最优着色形式。
In this paper, we investigate the randomness properties of sequences in $\mathbb{Z}_v$ derived from permutations in $\mathbb{Z}_{p}^*$ using the remainder function modulo $v$, where $p$ is a prime integer. Motivated by earlier studies with a cryptographic focus we compare sequences constructed from the ElGamal function $x \to g^x$ for $x\in\mathbb{Z}_{>0}$ and $g$ a primitive element of $\mathbb{Z}_{p}^*$, to sequences constructed from random permutations of $\mathbb{Z}_{p}^*$. We prove that sequences obtained from ElGamal have maximal period and behave similarly to random permutations with re…
A graph $G$ is called a complete $k$-partite ($k\geq 2$) graph if its vertices can be partitioned into $k$ independent sets $V_{1},...,V_{k}$ such that each vertex in $V_{i}$ is adjacent to all the other vertices in $V_{j}$ for $1\leq i<j\leq k$. A complete $k$-partite graph $G$ is a complete balanced $k$-partite graph if $|V_{1}| = |V_{2}| =... = |V_{k}|$. An edge-coloring of a graph $G$ with colors $1,...,t$ is an interval $t$-coloring if all colors are used, and the colors of edges incident to each vertex of $G$ are distinct and form an interval of integers. A graph $G$ is interval colorabl…
For a subgraph $G$ of the blow-up of a graph $F$, we let $δ^*(G)$ be the smallest minimum degree over all of the bipartite subgraphs of $G$ induced by pairs of parts that correspond to edges of $F$. In [Triangle-factors in a balanced blown-up triangle. Discrete Mathematics, 2000], Johansson proved that if $G$ is a spanning subgraph of the blow-up of $C_3$ with parts of size $n$ and $δ^*(G) \ge \frac{2}{3}n + \sqrt{n}$, then $G$ contains $n$ vertex-disjoint triangles, and presented the following conjecture of Häggkvist: If $G$ is a spanning subgraph of the blow-up of $C_k$ with parts of size $n…
Dominated balanced separators in wheel-induced-minor-free graphs
本文证明了排除固定轮图作为诱导极小的图具有主导平衡分离器的性质。
Extremal bipartite independence number and balanced coloring
本文研究二分图极值问题，得到两个算法性的最优（差2倍内）结果：大平均度二分图的平衡独立集大小下界，以及最大度有界平衡二分图的平衡着色划分数上界，分别改进了已有定理。
An edge-coloring of a complete graph with a set of colors $C$ is called completely balanced if any vertex is incident to the same number of edges of each color from $C$. Erdős and Tuza asked in $1993$ whether for any graph $F$ on $\ell$ edges and any completely balanced coloring of any sufficiently large complete graph using $\ell$ colors contains a rainbow copy of $F$. This question was restated by Erdős in his list of ``Some of my favourite problems on cycles and colourings''. We answer this question in the negative for most cliques $F=K_q$ by giving explicit constructions of respective comp…
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