Results 61 to 70 of about 14,100 (298)

On Odd Covers of Cliques and Disjoint Unions

Journal of Graph Theory, EarlyView.
ABSTRACT Babai and Frankl posed the “odd cover problem” of finding the minimum cardinality of a collection of complete bipartite graphs such that every edge of the complete graph of order n $n$ is covered an odd number of times. In a previous paper with O'Neill, some of the authors proved that this value is always ⌈ n / 2 ⌉ $\lceil n/2\rceil $ or ⌈ n /
Calum Buchanan, Alexander Clifton, Eric Culver, Péter Frankl, Jiaxi Nie, Kenta Ozeki, Puck Rombach, Mei Yin   +7 more
wiley   +1 more source

Flexible List Coloring of Graphs With Maximum Average Degree Less Than 3

Journal of Graph Theory, EarlyView.
ABSTRACT In the flexible list coloring problem, we consider a graph G $G$ and a color list assignment L $L$ on G $G$, as well as a subset U ⊆ V ( G ) $U\subseteq V(G)$ for which each u ∈ U $u\in U$ has a preferred color p ( u ) ∈ L ( u ) $p(u)\in L(u)$. Our goal is to find a proper L $L$‐coloring ϕ $\phi $ of G $G$ such that ϕ ( u ) = p ( u ) $\phi (u)=
Richard Bi, Peter Bradshaw
wiley   +1 more source

On Relative Stability for Strongly Mixing Sequences

Foundations
We consider a class of strongly mixing sequences with infinite second moment. This class contains important GARCH processes that are applied in econometrics. We show the relative stability for such processes and construct a counterexample. We apply these
Adam Jakubowski, Zbigniew Stanisław Szewczak   +1 more
doaj   +1 more source

Are There Good Mistakes? A Theoretical Analysis of CEGIS [PDF]

Electronic Proceedings in Theoretical Computer Science, 2014
Counterexample-guided inductive synthesis CEGIS is used to synthesize programs from a candidate space of programs. The technique is guaranteed to terminate and synthesize the correct program if the space of candidate programs is finite. But the technique
Susmit Jha, Sanjit A. Seshia
doaj   +1 more source

A counterexample to the “composition conjecture" [PDF]

Proceedings of the American Mathematical Society, 2002
In this note we construct a class of counterexamples to the “composition conjecture" concerning an infinitesimal version of the center problem for the polynomial Abel equation in the complex domain.
openaire   +3 more sources

Path Degeneracy and Applications

Journal of Graph Theory, EarlyView.
ABSTRACT In this work, we relate girth and path‐degeneracy in classes with sub‐exponential expansion, with explicit bounds for classes with polynomial expansion and proper minor‐closed classes that are tight up to a constant factor (and tight up to second order terms if a classical conjecture on existence of g $g$‐cages is verified). As an application,
Yuquan Lin, Patrice Ossona de Mendez
wiley   +1 more source

On the Stanley Depth of Powers of Monomial Ideals

Mathematics, 2019
In 1982, Stanley predicted a combinatorial upper bound for the depth of any finitely generated multigraded module over a polynomial ring. The predicted invariant is now called the Stanley depth. Duval et al.
S. A. Seyed Fakhari
doaj   +1 more source

A counterexample to a conjecture of abbott

Journal of Combinatorial Theory, Series A, 1989
Arguments using elementary number theory are used to construct counterexamples to a conjecture of Abbott.
openaire   +1 more source

On Sparsity Conditions Guaranteeing a Fractional Coloring

Journal of Graph Theory, EarlyView.
ABSTRACT A graph has an ( a : b ) $(a:b)$ ‐coloring if there exists an assignment from the vertices to subsets of { 1 , … , a } $\{1,\ldots ,a\}$ with size b $b$ such that adjacent vertices are assigned disjoint subsets. Odd girth at least 2 k + 1 $2k+1$ is a necessary condition for a graph to have a ( 2 k + 1 : k ) $(2k+1:k)$‐coloring.
Ilkyoo Choi
wiley   +1 more source

Obstructions for Homomorphisms to Odd Cycles in Series‐Parallel Graphs

Journal of Graph Theory, EarlyView.
ABSTRACT For a graph H $H$, an H $H$‐colouring of a graph G $G$ is a vertex mapping ϕ : V ( G ) → V ( H ) $\phi :V(G)\to V(H)$ such that adjacent vertices are mapped to adjacent vertices. A graph G $G$ is C 2 k + 1 ${C}_{2k+1}$‐critical if G $G$ has no C 2 k + 1 ${C}_{2k+1}$‐colouring but every proper subgraph of G $G$ has a C 2 k + 1 ${C}_{2k+1 ...
Eun‐Kyung Cho, Ilkyoo Choi, Boram Park, Mark Siggers   +3 more
wiley   +1 more source