Abstract
Za dani graf ▫$G$▫ je Steinerjev interval množice vozlišč ▫$W \subset V(G)$▫ množica tistih vozlišč, ki ležijo na kakem Steinerjevem drevesu glede na ▫$W$▫. Množica ▫$U \subset V(G)$▫ je ▫$g_3$▫-konveksna v ▫$G$▫, če Steinerjev interval poljubne trojice vozlišč iz ▫$U$▫ v celoti leži v ▫$U$▫. Henning, Nielsen in Oellermann (2009) so dokazali, da graf ▫$G$▫, v katerem so ▫$j$▫-krogle ▫$g_3$▫-konveksne za vsak ▫$j \ge 1$▫, ne vsebuje hiše niti grafov dvojčkov ▫$C_4$▫ kot induciranih podgrafov in vsak cikel v ▫$G$▫ dolžine vsaj šest je dobro premostljiv. V tem članku dokažemo, da velja tudi obrat tega izreka, s čimer okarakteriziramo grafe z ▫$g_3$▫-konveksnimi kroglami.
Keywords
matematika;teorija grafov;Steinerjev interval;razdalja;dobra premostljivost;mathematics;graph theory;Steiner interval;distance;well-bridgeness;
Data
Language: |
English |
Year of publishing: |
2011 |
Typology: |
1.01 - Original Scientific Article |
Organization: |
UM FERI - Faculty of Electrical Engineering and Computer Science |
UDC: |
519.17 |
COBISS: |
16079193
|
ISSN: |
0195-6698 |
Views: |
248 |
Downloads: |
17 |
Average score: |
0 (0 votes) |
Metadata: |
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Other data
Secondary language: |
English |
Secondary title: |
O lokalni 3-Steinerjevi konveksnosti |
Secondary abstract: |
Given a graph ▫$G$▫ and a set of vertices ▫$W \subset V(G)$▫, the Steiner interval of ▫$W$▫ is the set of vertices that lie on some Steiner tree with respect to ▫$W$▫. A set ▫$W \subset V(G)$▫ is called ▫$g_3$▫-convex in ▫$G$▫, if the Steiner interval with respect to any three vertices from ▫$U$▫ lies entirely in ▫$U$▫. Henning et al. (2009) proved that if every ▫$j$▫-ball for all ▫$j \ge 1$▫ is ▫$g_3$▫-convex in a graph ▫$G$▫, then ▫$G$▫ has no induced house nor twin ▫$C_4$▫, and every cycle in ▫$G$▫ of length at least six is well-bridged. In this paper we show that the converse of this theorem is true, thus characterizing the graphs in which all balls are ▫$g_3$▫-convex. |
Secondary keywords: |
matematika;teorija grafov;Steinerjev interval;razdalja;dobra premostljivost; |
URN: |
URN:SI:UM: |
Type (COBISS): |
Not categorized |
Pages: |
str. 1222-1235 |
Volume: |
Vol. 32 |
Issue: |
no. 8 |
Chronology: |
2011 |
ID: |
1475890 |