1. Suppose G is 26-regular on 105 vertices. Assume that for any two adjacent vertices, they share 13 neighbors, and for
Posted: Fri Apr 29, 2022 12:08 pm
1. Suppose G is 26-regular on 105 vertices. Assume that for any two adjacent vertices, they share 13 neighbors, and for any two non-adjacent vertices, they share 4 common neighbors. (a) If A is the adjacency matrix for the graph, determine the entries of AP in 3 cases for (i, j): When i = j, when i is adjacent to j, and when i is NOT adjacent to j. (b) Express A’ in terms of A, I, and all ones matrix J. (C) We know k = 26 is an eigenvalue with multiplicity 1. If v is any other eigenvector (not associated with k = 26), determine all other distinct eigenvalues by applying v to the equation in the previous step. (d) Set up two equations and solve them to determine the multiplicities of the re- maining eigenvalues.