Equilibrium Strategies for the N-agent Mean-Variance Investment Problem over a Random Horizon

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Hauptverfasser: Liang, Xiaoqing, Xiong, Jie, Yang, Ying
Format: Preprint
Veröffentlicht: 2025
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author Liang, Xiaoqing
Xiong, Jie
Yang, Ying
author_facet Liang, Xiaoqing
Xiong, Jie
Yang, Ying
contents We study equilibrium feedback strategies for a family of dynamic mean-variance problems with competition among a large group of agents. We assume that the time horizon is random and each agent's risk aversion depends dynamically on the current wealth. We consider both the finite population game and the corresponding mean-field one. Each agent can invest in a risk-free asset and a specific individual stock, which is correlated with other stocks by a common noise. By applying stochastic control theory, we derive the extended Hamilton-Jacobi-Bellman (HJB) system of equations for both $n$-agent and mean-field games. Under an exponentially distributed random horizon, in each case, we explicitly obtain the equilibrium feedback strategies and the value function. Our results show that the agent's equilibrium feedback strategy depends not only on his/her current wealth but also on the wealth of other competitors. Moreover, when the risk aversion is state-independent and the risk-free interest rate is zero, the equilibrium strategies degenerate to constants, which is identical to the unique equilibrium obtained in \citet{lacker2019mean} with exponential risk preferences; when the competition parameter goes to zero and the risk aversion equals some specific value, the equilibrium strategies coincide with the ones derived in \citet{landriault2018equilibrium}.
format Preprint
id arxiv_https___arxiv_org_abs_2507_04611
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Equilibrium Strategies for the N-agent Mean-Variance Investment Problem over a Random Horizon
Liang, Xiaoqing
Xiong, Jie
Yang, Ying
Optimization and Control
93E20, 91G10, 91G80, 60H30
We study equilibrium feedback strategies for a family of dynamic mean-variance problems with competition among a large group of agents. We assume that the time horizon is random and each agent's risk aversion depends dynamically on the current wealth. We consider both the finite population game and the corresponding mean-field one. Each agent can invest in a risk-free asset and a specific individual stock, which is correlated with other stocks by a common noise. By applying stochastic control theory, we derive the extended Hamilton-Jacobi-Bellman (HJB) system of equations for both $n$-agent and mean-field games. Under an exponentially distributed random horizon, in each case, we explicitly obtain the equilibrium feedback strategies and the value function. Our results show that the agent's equilibrium feedback strategy depends not only on his/her current wealth but also on the wealth of other competitors. Moreover, when the risk aversion is state-independent and the risk-free interest rate is zero, the equilibrium strategies degenerate to constants, which is identical to the unique equilibrium obtained in \citet{lacker2019mean} with exponential risk preferences; when the competition parameter goes to zero and the risk aversion equals some specific value, the equilibrium strategies coincide with the ones derived in \citet{landriault2018equilibrium}.
title Equilibrium Strategies for the N-agent Mean-Variance Investment Problem over a Random Horizon
topic Optimization and Control
93E20, 91G10, 91G80, 60H30
url https://arxiv.org/abs/2507.04611