Average distance and independence number
2nd Twente workshop on Graphs and combinatorial optimization
On acyclic conjugated molecules with minimal energies
Discrete Applied Mathematics
Introduction to Algorithms
On acyclic systems with minimal Hosoya index
Discrete Applied Mathematics
Trees with m-matchings and the fourth and fifth minimal Hosoya index
Computers & Mathematics with Applications
On the minimal energy ordering of trees with perfect matchings
Discrete Applied Mathematics
The largest Hosoya index of (n,n+1)-graphs
Computers & Mathematics with Applications
On some forests determined by their Laplacian or signless Laplacian spectrum
Computers & Mathematics with Applications
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Let G be a simple undirected graph with the characteristic polynomial of its Laplacian matrix L(G), P(G,@m)=@?"k"="0^n(-1)^kc"k@m^n^-^k. It is well known that for trees the Laplacian coefficient c"n"-"2 is equal to the Wiener index of G, while c"n"-"3 is equal to the modified hyper-Wiener index of the graph. In this paper, we characterize n-vertex trees with given matching number m which simultaneously minimize all Laplacian coefficients. The extremal tree A(n,m) is a spur, obtained from the star graph S"n"-"m"+"1 with n-m+1 vertices by attaching a pendant edge to each of certain m-1 non-central vertices of S"n"-"m"+"1. In particular, A(n,m) minimizes the Wiener index, the modified hyper-Wiener index and the recently introduced Incidence energy of trees, defined as IE(G)=@?"k"="0^n@m"k, where @m"k are the eigenvalues of signless Laplacian matrix Q(G)=D(G)+A(G). We introduced a general @r transformation which decreases all Laplacian coefficients simultaneously. In conclusion, we illustrate on examples of Wiener index and Incidence energy that the opposite problem of simultaneously maximizing all Laplacian coefficients has no solution.