The Nordhaus-Gaddum-type inequalities for the Nirmala indices

Abstract

Nowadays, deducing the bounds and relations between known topological indices is an interesting tool in Chemical Graph Theory (CGT). This article investigates the mathematical properties of the recently defined Nirmala indices in terms of some graph invariants. At the outset, we establish some mathematical relations between the Nirmala indices (Nirmala index, first and second inverse Nirmala indices) and other well-established degree-based topological indices. Then, some Nordhaus-Gaddum-type inequalities for the combination of the Nirmala indices of a graph and its complement are obtained.