Nonseparating Cycles Avoiding Specific Vertices

Thomassen proved that every k+3-connected graph G contains an induced cycle C such that G-VC is k-connected, establishing a conjecture of Lovasz. In general, one could ask the following question: For any positive integers k,l, does there exist a smallest positive integer gk,l such that for any gk,l-connected graph G, any Xi¾?VG with |X|=k, and any e∈EG-X, there is an induced cycle C in G-X such that e∈EC and G-VC is l-connected? The case when k=0 is a well-known conjecture of Lovasz that is still open for li¾?3. In this article, we prove gk,1i¾?10k+1 and gk,2i¾?10k+11. We also consider a weaker version: For any positive integers k,l, is there a smallest positive integer fk,l such that for every fk,l-connected graph G and any Xi¾?VG with |X|=k, there is an induced cycle C in G-X such that G-VC is l-connected? The case when k=0 was studied by Thomassen. We prove fk,li¾?2k+l+2 and fk,1=k+3.

[1]  Richard H. Schelp,et al.  Problems in Graph Theory from Memphis , 2013, The Mathematics of Paul Erdős II.

[2]  Béla Bollobás,et al.  Highly linked graphs , 1996, Comb..

[3]  William T. Tutte,et al.  A theory of 3-connected graphs , 1961 .

[4]  Bruce A. Reed,et al.  A weaker version of Lovász' path removal conjecture , 2008, J. Comb. Theory, Ser. B.

[5]  Wolfgang Mader Topological minors in graphs of minimum degree n , 1997, Contemporary Trends in Discrete Mathematics.

[6]  Ken-ichi Kawarabayashi,et al.  Non-Separating Paths in 4-Connected Graphs , 2005 .

[7]  Yoshimi Egawa Contractible Cycles in Graphs with Girth at Least 5 , 1998, J. Comb. Theory, Ser. B.

[8]  H. Jung Eine Verallgemeinerung desn-fachen Zusammenhangs für Graphen , 1970 .

[9]  Xingxing Yu,et al.  Graph Connectivity After Path Removal , 2003, Comb..

[10]  Carsten Thomassen,et al.  Graph decomposition with applications to subdivisions and path systems modulo k , 1983, J. Graph Theory.

[11]  Paul Wollan,et al.  An improved linear edge bound for graph linkages , 2005, Eur. J. Comb..

[12]  Yoshimi Egawa,et al.  Cycles in k-connected graphs whose deletion results in a (k-2)-connected graph , 1987, J. Comb. Theory, Ser. B.

[13]  Xingxing Yu Non-separating cycles and discrete Jordan curves , 1992, J. Comb. Theory, Ser. B.

[14]  Carsten Thomassen,et al.  Nonseparating cycles in K-Connected graphs , 1981, J. Graph Theory.

[15]  Nicola Martinov Uncontractable 4-connected graphs , 1982, J. Graph Theory.

[16]  Matthias Kriesell Induced paths in 5-connected graphs , 2001 .