Abstract
A long-standing conjecture asserts that there exists a constant \(c>0\) such that every graph of order n without isolated vertices contains an induced subgraph of order at least cn with all degrees odd. Scott (Comb Probab Comput 1:335–349, 1992) proved that every graph G has an induced subgraph of order at least \(|V(G)|/(2\chi (G))\) with all degrees odd, where \(\chi (G)\) is the chromatic number of G, this implies the conjecture for graphs with bounded chromatic number. But the factor \(1/(2\chi (G))\) seems to be not best possible, for example, Radcliffe and Scott (Discrete Math 275–279, 1995) proved \(c=\frac{2}{3}\) for trees, Berman et al. (Aust J Comb 81–85, 1997) showed that \(c=\frac{2}{5}\) for graphs with maximum degree 3, so it is interesting to determine the exact value of c for special family of graphs. In this paper, we further confirm the conjecture for graphs with treewidth at most 2 with \(c=\frac{2}{5}\), and the bound is best possible.
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References
Berman, D.M., Wang, H., Wargo, L.: Odd induced subgraphs in graphs of maximum degree three. Aust. J. Comb. 15, 81–85 (1997)
Caro, Y.: On induced subgraphs with odd degrees. Discrete Math. 132, 23–28 (1994)
Diestel, R.: Graph Theory. Springer, New York (2000)
Lih, K.W., Wang, W.F., Zhu, X.D.: Coloring the square of a \(K_4\)-minor free graph. Discrete Math. 269, 303–309 (2003)
Lovász, L.: Combinatorial Problems and Exercises. North-Holland, Amsterdam (1979)
Radcliffe, A.J., Scott, A.D.: Every tree contains a large induced subgraph with all degrees odd. Discrete Math. 140, 275–279 (1995)
Scott, A.D.: Large induced subgraphs with all degrees odd. Comb. Probab. Comput. 1, 335–349 (1992)
Acknowledgements
The work was supported by NNSF of China (no. 11671376) and NSF of Anhui Province (no. 1708085MA18) and the Fundamental Research Funds for the Central Universities.
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Hou, X., Yu, L., Li, J. et al. Odd Induced Subgraphs in Graphs with Treewidth at Most Two. Graphs and Combinatorics 34, 535–544 (2018). https://doi.org/10.1007/s00373-018-1892-x
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DOI: https://doi.org/10.1007/s00373-018-1892-x