On maximizing the second smallest eigenvalue of a state-dependent graph Laplacian

We consider the set /spl Gscr/ consisting of graphs of fixed order and weighted edges. The vertex set of graphs in /spl Gscr/ will correspond to point masses and the weight for an edge between two vertices is a functional of the distance between them. We pose the problem of finding the best vertex positional configuration in the presence of an additional proximity constraint, in the sense that, the second smallest eigenvalue of the corresponding graph Laplacian is maximized. In many recent applications of algebraic graph theory in systems and control, the second smallest eigenvalue of Laplacian has emerged as a critical parameter that influences the stability and robustness properties of dynamic systems that operate over an information network. Our motivation in the present work is to "assign" this Laplacian eigenvalue when relative positions of various elements dictate the interconnection of the underlying weighted graph. In this venue one would then be able to "synthesize" information graphs that have desirable system theoretic properties.