On the complexity of moving vertices in a graph
We consider the problem of deciding whether a given graph G has an automorphism which moves at least k vertices (where k is a function of |V(G)|), a question originally posed by Lubiw (1981). Here we show that this problem is equivalent to the one of deciding whether a graph has a nontrivial automor...
| Autores: | , |
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| Tipo de recurso: | informe técnico |
| Fecha de publicación: | 1998 |
| País: | España |
| Institución: | Universitat Politècnica de Catalunya (UPC) |
| Repositorio: | UPCommons. Portal del coneixement obert de la UPC |
| Idioma: | inglés |
| OAI Identifier: | oai:upcommons.upc.edu:2117/97145 |
| Acceso en línea: | https://hdl.handle.net/2117/97145 |
| Access Level: | acceso abierto |
| Palabra clave: | Automorphism Complexity Graph isomorphism Àrees temàtiques de la UPC::Informàtica::Programació |
| Sumario: | We consider the problem of deciding whether a given graph G has an automorphism which moves at least k vertices (where k is a function of |V(G)|), a question originally posed by Lubiw (1981). Here we show that this problem is equivalent to the one of deciding whether a graph has a nontrivial automorphism, when k is O((log n)/(log log n)). It is commonly believed that deciding isomorphism between two graphs is strictly harder than deciding whether a graph has a nontrivial automorphism. Indeed, we show that an isomorphism oracle would improve the above result slightly---using such an oracle, one can decide whether there is an automorphism which moves at least k' vertices, where k is O(log n). If P is different from NP and Graph Isomorphism is not NP-complete, the above results are fairly tight, since it is known that deciding if there is an automorphism which moves at least n^e vertices, for any fixed e in (0, 1), is NP-complete. In other words, a substantial improvement of our result would settle some fundamental open problems about Graph Isomorphism. |
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