Longest cycles in k-connected graphs with given independence number
نویسندگان
چکیده
The Chvátal–Erdős Theorem states that every graph whose connectivity is at least its independence number has a spanning cycle. In 1976, Fouquet and Jolivet conjectured an extension: If G is an n-vertex k-connected graph with independence number a, and a ≥ k, then G has a cycle with length at least k(n+a−k) a . We prove this conjecture.
منابع مشابه
Intersections of Longest Cycles in k-Connected Graphs
Let G be a connected graph, where k2. S. Smith conjectured that every two longest cycles of G have at least k vertices in common. In this note, we show that every two longest cycles meet in at least ck 3Â5 vertices, where cr0.2615. 1998 Academic Press In this note, we provide a lower bound on the number of vertices in the intersection of any two longest cycles in a k-connected graph (k2). This ...
متن کاملDominating cycles in triangle-free graphs
A cycle C in a graph G is said to be dominating if E(G−C) = ∅. Enomoto et al. showed that if G is a 2-connected triangle-free graph with α(G) ≤ 2κ(G) − 2, then every longest cycle is dominating. But it is unknown whether the condition on the independence number is sharp. In this paper, we show that if G is a 2-connected triangle-free graph with α(G) ≤ 2κ(G) − 1, then G has a longest cycle which...
متن کاملThe locating chromatic number of the join of graphs
Let $f$ be a proper $k$-coloring of a connected graph $G$ and $Pi=(V_1,V_2,ldots,V_k)$ be an ordered partition of $V(G)$ into the resulting color classes. For a vertex $v$ of $G$, the color code of $v$ with respect to $Pi$ is defined to be the ordered $k$-tuple $c_{{}_Pi}(v)=(d(v,V_1),d(v,V_2),ldots,d(v,V_k))$, where $d(v,V_i)=min{d(v,x):~xin V_i}, 1leq ileq k$. If distinct...
متن کاملIndependence Number and Disjoint Theta Graphs
The goal of this paper is to find vertex disjoint even cycles in graphs. For this purpose, define a θ-graph to be a pair of vertices u, v with three internally disjoint paths joining u to v. Given an independence number α and a fixed integer k, the results contained in this paper provide sharp bounds on the order f(k, α) of a graph with independence number α(G) ≤ α which contains no k disjoint ...
متن کاملRemovable Cycles in 2-connected Graphs of Minimum Degree at Least Four
The lower bound on the length of 'removable' cycles in Theorem 1 is essentially best possible since there exist 2-connected simple graphs of minimum degree k whose longest 'removable' cycle has length k + i. Moreover, for the special case k = 4, we can construct 2-connected, 4-regular simple graphs whose longest 'removable' cycle has length four. The following counterexample which was independe...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
- J. Comb. Theory, Ser. B
دوره 101 شماره
صفحات -
تاریخ انتشار 2009