Abstract. In this note, we consider the large and moderate deviation principle of the estimators of the integrated covariance of two-dimensional diffusion processes when they are observed only at discrete times in a synchronous manner. The proof is extremely simple. It is essentially an application of the contraction principle for the results given in the case of the volatility [4].AMS 2000 subject classifications: 60F10, 62J05, 60J05.
Motivation and contextGiven a filtred probability space (Ω, F, (F t ), P), let (X 1,t , X 2,t ) be a two dimensional diffusion process given bywhere ((B 1,t , B 2,t ), t ≥ 0) is a two-dimensional Gaussian process with independent increments, zero mean and covariance matrixIn (1.1), (u 1 , u 2 ) is a progressively measurable process (possibly unknown). In what follows, we restrict our attention to the case when σ 1 , σ 2 and ρ are deterministic functions; the functions σ i , i = 1, 2 take positive values while ρ takes values in the interval [−1, 1]. Note that the marginal processes B 1 and B 2 are Brownian motions (BM). Moreover, we can define a process B * t such that (B 1,t , B * t ) t≥0 is a two-dimensional BM and dB 2,t = ρ t dB 1,t + 1 − ρ 2 t dB * t for every t ≥ 0. In this note, the parameter of interest is the (deterministic) covariance of X 1 and X 2(1.2)In finance, X 1 , X 2 · is the integrated covariance (over [0, 1]) of the logarithmic prices X 1 and X 2 of two securities. It is an essential quantity to be measured for risk management purposes. The covariance for multiple price processes is of great interest in many financial applications. The naive estimator is the realized covariance, which is the analogue of realized variance for a single process.Typically X 1,t and X 2,t are not observed in continuous time but we have only discrete time observations. Given discrete equally spaced observation (X 1,t n k , X 2,t n k , k = 1, · · · , n) in Date: October 11, 2013.