Mean Field Game of Optimal Relative Investment with Contagious Risk

This paper studies a mean field game (MFG) problem in a market with a large population of heterogeneous agents. Each agent aims to maximize the terminal wealth under a CRRA type relative performance, in which the interaction occurs by the competition with peers. We start from the model with n agents, in which the underlying risky assets subject to a common noise and contagious jump risk modelled by a multi-dimensional Hawkes process. With a continuum of agents, we formulate the MFG problem and characterize a deterministic mean field equilibrium in an analytical form, allowing us to investigate some impacts of model parameters in the limiting model and discuss the financial implications. More importantly, it is shown that this mean field equilibrium can serve as an approximate Nash equilibrium for the n-player game problem when n is sufficiently large. The explicit order of the approximation error is also derived.