... distance is not equal toafixedδ∈{1, ,n}, then a pair of disconnected sets becomes an equidistant code pair.For disconnected sets A and Bwe will give a bound for|A|·|B|in terms of the eigenvalues ... ,q}n,thesetofwordsoflengthnoveranalphabetofsizeq,anddefinetwowordstobeinrelationRδiftheirHammingdistance(thenumberofcoordinateplacesinwhichtheydiffer)equalsδ.ThisdefinesthewellknownHammingassociationschemeH(n,q).ForagraphGδinH(n,q)twodisconnectedsetsinGδarecalledequidistantcodepairs(atdistanceδ)andwewriteΦδ and δinsteadofΦ(Gδ )and (Gδ)respectively.Lemma3.1Φ2δ≥max0≤δ≤δn−δδ−δ(q−1)δ−δq2q2δ.Proof.TakeforAthesetofwords(x1, ... eigenvalues and graphs, Linear AlgebraAppl. 226-228 (1995), 593-616.[12] L. Lov´asz, On the Shannon capacity of a graph, IEEE Trans. Inform.Theory 25 (1979), 1-7. Disconnected vertex sets and equidistant...