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We prove that for a connected simple graph $G$ with $nle 10$ vertices, and two longest paths $C$ and $D$ in $G$, the intersection of vertex sets $V(C)cap V(D)$ is a separator. This shows that the graph found previously with $n=11$, in which the complement of the intersection of vertex sets $V(C)cap V(D)$ of two longest paths is connected, is minimal.
In 1966, Gallai asked whether all longest paths in a connected graph share a common vertex. Counterexamples indicate that this is not true in general. However, Gallais question is positive for certain well-known classes of connected graphs, such as s
Let $P,Q$ be longest paths in a simple graph. We analyze the possible connections between the components of $Pcup Qsetminus (V(P)cap V(Q))$ and introduce the notion of a bi-traceable graph. We use the results for all the possible configurations of th
Given integers $k,j$ with $1le j le k-1$, we consider the length of the longest $j$-tight path in the binomial random $k$-uniform hypergraph $H^k(n,p)$. We show that this length undergoes a phase transition from logarithmic length to linear and deter
We exhibit a pseudogroup of smooth local transformations of the real line which is compactly generated, but not realizable as the holonomy pseudogroup of a foliation of codimension 1 on a compact manifold. The proof relies on a description of all fol
Let $f(n,H)$ denote the maximum number of copies of $H$ possible in an $n$-vertex planar graph. The function $f(n,H)$ has been determined when $H$ is a cycle of length $3$ or $4$ by Hakimi and Schmeichel and when $H$ is a complete bipartite graph wit