Maximizing algebraic connectivity for certain families of graphs

Abstract: We investigate the bounds on algebraic connectivity of graphs subject to constraints on the number of edges, vertices, and topology. We show that the algebraic connectivity for any tree on $n$ vertices and with maximum degree $d$ is bounded above by $2(d-2) \frac{1}{n}+O(\frac{\ln n}{n^{2}}).$ We then investigate upper bounds on algebraic connectivity for cubic graphs. We show that algebraic connectivity of a cubic graph of girth $g$ is bounded above by $3-2^{3/2}\cos(\pi/\lfloor g/2\rfloor) ,$ which is an improvement over the bound found by Nilli [A. Nilli, Electron. J. Combin., 11(9), 2004]. Finally, we propose several conjectures and open questions.