On Parameterized Complexity of Binary Networked Public Goods Game

In the Binary Networked Public Goods (BNPG for short) game, every player needs to decide if she participates in a public project whose utility is shared equally by the community. We study the problem of deciding if there exists a pure strategy Nash equilibrium (PSNE) in such games. The problem is already known to be NP-complete. This casts doubt on predictive power of PSNE in BNPG games. We provide fine-grained analysis of this problem under the lens of parameterized complexity theory. We consider various natural graph parameters and show W[1]-hardness, XP, and FPT results. Hence, our work significantly improves our understanding of BNPG games where PSNE serves as a reliable solution concept. We finally prove that some graph classes, for example path, cycle, bi-clique, and complete graph, always have a PSNE if the utility function of the players are same.