Precise large deviations for sums of random variables with consistently varying tails

Let {Xk, k ¿ 1} be a sequence of independent, identically distributed nonnegative random variables with common distribution function F and finite expectation ¿ > 0. Under the assumption that the tail probability F¿(x) = 1 - F(x) is consistently varying as x tends to infinity, this paper investigates precise large deviations for both the partial sums Sn and the random sums SN(t), where N(·) is a counting process independent of the sequence {Xk, k ¿ 1}. The obtained results improve some related classical ones. Applications to a risk model with negatively associated claim occurrences and to a risk model with a doubly stochastic arrival process (extended Cox process) are proposed.