Some Results About a Conjecture on Identifying Codes in Complete Suns
Résumé
Consider a graph G = (V, E) and, for every vertex v ∈ V , denote by B(v) the set {v} ∪ {u : uv ∈ E}. A subset C ⊆ V is an identifying code if the sets B(v) ∩ C, v ∈ V , are all nonempty and distinct. It is a locating-dominating code if the sets B(v) ∩ C, v ∈ V \ C, are all nonempty and distinct. Let S n be the graph whose vertex set can be partitioned into two sets U n and V n , where U n = {u 1 , u 2 ,. .. , u n } induces a clique, and V n = {v 1,2 , v 2,3 ,. .. , v n−1,n , v n,1 } induces an independent set, with edges v i,i+1 u i and v i,i+1 u i+1 , 1 ≤ i ≤ n; computations are carried modulo n. This graph is called a complete sun. We prove the conjecture, stated by Argiroffo, Bianchi and Wagler in 2014, that the smallest identifying code in S n has size equal to n. We also characterize and count all the identifying codes with size n in S n. Finally, we determine the sizes of the smallest locating-dominating codes in S n .
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