An extremal problem for some classes of oriented graphs
K. Howalla, Abdallah N. Dabboucy, R. Tout (1983)
Časopis pro pěstování matematiky
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K. Howalla, Abdallah N. Dabboucy, R. Tout (1983)
Časopis pro pěstování matematiky
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Domingo Pestana, José Rodríguez, José Sigarreta, María Villeta (2012)
Open Mathematics
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If X is a geodesic metric space and x 1; x 2; x 3 ∈ X, a geodesic triangle T = {x 1; x 2; x 3} is the union of the three geodesics [x 1 x 2], [x 2 x 3] and [x 3 x 1] in X. The space X is δ-hyperbolic (in the Gromov sense) if any side of T is contained in a δ-neighborhood of the union of the two other sides, for every geodesic triangle T in X. We denote by δ(X) the sharp hyperbolicity constant of X, i.e., δ(X) = inf {δ ≥ 0: X is δ-hyperbolic}. We obtain information about the hyperbolicity...
Wu, Yaokun, Zhang, Chengpeng (2011)
The Electronic Journal of Combinatorics [electronic only]
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Felix Joos (2015)
Discussiones Mathematicae Graph Theory
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As observed by Rautenbach and Sereni [SIAM J. Discrete Math. 28 (2014) 335-341] there is a gap in the proof of the theorem of Balister et al. [Combin. Probab. Comput. 13 (2004) 311-317], which states that the intersection of all longest paths in a connected circular arc graph is nonempty. In this paper we close this gap.
José M. Rodríguez, José M. Sigarreta (2017)
Open Mathematics
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If X is a geodesic metric space and x1, x2, x3 ∈ X, a geodesic triangle T = {x1, x2, x3} is the union of the three geodesics [x1x2], [x2x3] and [x3x1] in X. The space X is δ-hyperbolic (in the Gromov sense) if any side of T is contained in a δ-neighborhood of the union of the two other sides, for every geodesic triangle T in X. Deciding whether or not a graph is hyperbolic is usually very difficult; therefore, it is interesting to find classes of graphs which are hyperbolic. A graph...
K. Howalla, Abdallah N. Dabboucy, R. Tout (1982)
Časopis pro pěstování matematiky
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Branković, Ljiljana, Miller, Mirka, Plesník, Ján, Ryan, Joe, Širáň, Jozef (1998)
The Electronic Journal of Combinatorics [electronic only]
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Hassler Whitney (1933)
Fundamenta Mathematicae
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