versión impresa ISSN 0716-0917
ROJO, OSCAR. THE SPECTRUM OF THE LAPLACIAN MATRIX OF A BALANCED 2p-ARY TREE. Proyecciones (Antofagasta) [online]. 2004, vol.23, n.2, pp. 131-149. ISSN 0716-0917. doi: 10.4067/S0716-09172004000200006.
Let p > 1 be an integer. We consider an unweighted balanced tree Bpk of k levels with a root vertex of degree 2p, vertices from the level 2 until the level (k - 1) of degree 2p +1 and vertices in the level k of degree 1. The case p = 1 it was studied in [8, 9, 10]. We prove that the spectrum of the Laplacian matrix L (Bpk) is σ (L (Bpk)) = Ukj =1σ (T(p) j where, for 1< j < k < 1, T(p)j is the j ×j principal submatrix of the tridiagonal k×k singular matrix T(p)k , scanear fórmula We derive that the multiplicity of each eigenvalue of Tj , as an eigenvalue of L (Bpk) , is at least 2(2p-1)2(k-j-1)p . Moreover, we show that the multiplicity of the eigenvalue λ = 1 of L (Bpk) is exactly 2(2p-1)2(k-2)p. Finally, we prove that 3, 7 σ (L (B2k)) if and only if k is a multiple of 3, that 5 σ (L (B2k) if and only if k is an even number, and that no others integer eigenvalues exist for L (B2k).
Palabras clave : Tree; balanced tree; binary tree; n-ary tree; Laplacian matrix.