Let S be a subset of the units in Zn. Let be a circulant graph of order n (a Cayley graph of Zn) such that if ij E(), then i - j (mod n) S. Toida conjectured that if is another...
Several new undecidability results on isomorphism problems for automatic structures are shown: (i) The isomorphism problem for automatic equivalence relations is 0 1complete. (ii)...
We study the complexity of testing if two given matroids are isomorphic. The problem is easily seen to be in Σ p 2. In the case of linear matroids, which are represented over pol...