On distance Laplacian energy in terms of graph invariants

Ganie, Hilal A. ; Ul Shaban, Rezwan ; Rather, Bilal A. ; Pirzada, Shariefuddin

Czechoslovak Mathematical Journal, Tome 73 (2023) no. 2, pp. 335-353.

Résumé

For a simple connected graph $G$ of order $n$ having distance Laplacian eigenvalues $ \rho ^{L}_{1}\geq \rho ^{L}_{2}\geq \cdots \geq \rho ^{L}_{n}$, the distance Laplacian energy ${\rm DLE} (G)$ is defined as ${\rm DLE} (G)=\sum _{i=1}^{n}|\rho ^{L}_i-{2W(G)}/{n}|$, where $W(G)$ is the Wiener index of $G$. We obtain a relationship between the Laplacian energy and the distance Laplacian energy for graphs with diameter 2. We obtain lower bounds for the distance Laplacian energy ${\rm DLE} (G)$ in terms of the order $n$, the Wiener index $W(G)$, the independence number, the vertex connectivity number and other given parameters. We characterize the extremal graphs attaining these bounds. We show that the complete bipartite graph has the minimum distance Laplacian energy among all connected bipartite graphs and the complete split graph has the minimum distance Laplacian energy among all connected graphs with a given independence number. Further, we obtain the distance Laplacian spectrum of the join of a graph with the union of two other graphs. We show that the graph $K_{k}\bigtriangledown (K_{t}\cup K_{n-k-t})$, $1\leq t \leq \lfloor \frac {n-k}{2}\rfloor $, has the minimum distance Laplacian energy among all connected graphs with vertex connectivity $k$. We conclude this paper with a discussion on the trace norm of a matrix and the importance of our results in the theory of the trace norm of the matrix $D^L(G)-(2W(G)/n)I_n$.

Détail

DOI : 10.21136/CMJ.2023.0421-20

Classification : 05C12, 05C50, 15A18
Keywords: distance matrix; energy; distance Laplacian matrix; distance Laplacian energy