The rest of the paper is organized as follows. In Section 2, the
model and assumptions are given. In Section 3, we reduce the
partially observable control problem to an equivalent problem
with complete observations, and derive the generalized Hamilton–
Jacobi–Bellman equation. In Section 4, we investigate the existence
and uniqueness of the optimal reinsurance strategies
under both expected value principle and variance principle and
obtain the optimal reinsurance policies. Here, we also analyze the
effect of safety loading on the optimal reinsurance policies (in Sections
4.2 and 4.3). In Section 4.4, we investigate the influence of
the unobservable factors on the optimal reinsurance strategies,
and find that the optimal reinsurance strategy in the risk model
with unknown jump intensity is always less or equal to the one in the risk model with known intensity. Using the notion of generalized
Hamilton–Jacobi–Bellman equation we characterize the value
function, and prove that the optimal investment and reinsurance
policies we propose are optimal (in Section 4.5).