Universal graphs with a forbidden subtree

  title={Universal graphs with a forbidden subtree},
  author={Gregory L. Cherlin and Saharon Shelah},
  journal={J. Comb. Theory, Ser. B},
We show that the problem of the existence of universal graphs with specified forbidden subgraphs can be systematically reduced to certain critical cases by a simple pruning technique which simplifies the underlying structure of the forbidden graphs, viewed as trees of blocks. As an application, we characterize the trees T for which a universal countable T-free graph exists. 
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Keywords: infinite graphs ; universal graph ; forbidden subgraphs Note: Professor Pach's number: [034] Reference DCG-ARTICLE-1984-005 Record created on 2008-11-14, modified on 2017-05-12
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