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Title:Roots of cube polynomials of median graphs
Authors:ID Brešar, Boštjan (Author)
ID Klavžar, Sandi (Author)
ID Škrekovski, Riste (Author)
Files:URL http://www.imfm.si/preprinti/PDF/00887.pdf
 
Language:English
Work type:Not categorized
Organization:FERI - Faculty of Electrical Engineering and Computer Science
Abstract:Polinom kock ▫$c(G,X)$▫ grafa ▫$G$▫ je definiran z ▫$sum_{i ge 0}alpha_i(G)x^i$▫, kjer ▫$alpha_i(G)$▫ označuje število induciranih ▫$i$▫-kock v ▫$G$▫. Naj bo ▫$G$▫ medianski graf. Dokazano je, da je vsaka racionalna ničla polinoma ▫$c(G,x)$▫ oblike ▫$-frac{t+1}{t}$▫ za neko celo število ▫$t>0$▫ in da ima ▫$c(G,x)$▫ vedno realno ničlo na intervalu ▫$[-2,-1)$▫. Nadalje ima ▫$c(G,x)$▫ ▫$p$▫-kratno ničlo natanko tedaj, ko je ▫$G$▫ kartezični produkt ▫$p$▫ dreves istega reda. Grafi acikličnih kubičnih kompleksov so karakterizirani kot grafi za katere velja ▫$c(H,-2)=0$▫ za vsak 2-povezan konveksen podgraf ▫$H$▫.
Keywords:matematika, teorija grafov, polinom kock, koren, medianski graf, kartezični produkt grafov, mathematics, graph theory, cube polynomial, root, median graph, Cartesian product
Year of publishing:2003
Number of pages:str. 1-14
Numbering:Vol. 41, št. 887
PID:20.500.12556/DKUM-49369 New window
ISSN:1318-4865
UDC:519.17
COBISS.SI-ID:12590937 New window
NUK URN:URN:SI:UM:DK:QD0MTRJO
Publication date in DKUM:10.07.2015
Views:1559
Downloads:126
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Categories:Misc.
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Secondary language

Language:Unknown
Title:Koreni polinoma kock medianskih grafov
Abstract:The cube polynomial ▫$c(G,X)$▫ of a graph ▫$G$▫ is defined as ▫$sum_{i ge 0}alpha_i(G)x^i$▫, where ▫$alpha_i(G)$▫ denotes the number of induced ▫$i$▫-cubes of ▫$G$▫, in particular, ▫$alpha_0(G) = |V(G)|$▫ and ▫$alpha_1(G) = |E(G)|$▫. Let ▫$G$▫ be a median graph. It is proved that every rational zero of ▫$c(G,x)$▫ is of the form ▫$-frac{t+1}{t}$▫ for some integer ▫$t>0$▫ and that ▫$c(G,x)$▫ always has a real zero in the interval ▫$[-2,-1)$▫. Moreover, ▫$c(G,x)$▫ has a ▫$p$▫-multiple zero if and only if ▫$G$▫ is the cartesian product of ▫$p$▫ trees all of the same order. Graphs of acyclic cubical complexes are characterized as the graphs ▫$G$▫ for which ▫$c(H,-2)=0$▫ holds for every 2-connected convex subgraph ▫$H$▫ of ▫$G$▫. Median graphs that are Cartesian products are also characterized.


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