We derive a Karhunen-Loève expansion of the Gauss process B t − g(t) 1 0 g (u) dB u , t ∈ [0, 1], where (B t ) t∈[0,1] is a standard Wiener process and g : [0, 1] → R is a twice continuously differentiable function with g(0) = 0 and 1 0 (g (u)) 2 du = 1. This process is an important limit process in the theory of goodness-of-fit tests. We formulate two special cases with the function g(t) = √ 2 π sin(πt), t ∈ [0, 1], and g(t) = t, t ∈ [0, 1], respectively. The latter one corresponds to the Wiener bridge over [0, 1] from 0 to 0.
IntroductionIn this note we present a new class of Gauss processes, generalizing the Wiener bridge, for which Karhunen-Loève (KL) expansion can be given explicitly. We point out that there are only few Gauss processes for which the KL expansion is explicitly known. To give some examples, we mention the Wiener process (see, e.g., Ash and Gardner [5, Example 1.4.4]), the Ornstein-Uhlenbeck process (see, e.g., Papoulis [24, Problem 12.7] or Corlay and Pagès [10, Section 5.4 B]), the Wiener bridge (see, e.g., Deheuvels [12, Remark 1.1]), Kac-Kiefer-Wolfowitz process (see, Kac, Kiefer and Wolfowitz [16] and Nazarov and Petrova [23]), weighted Wiener processes and bridges (Deheuvels and Martynov [13]), Jandhyala-MacNeill process (Jandhyala and MacNeill [15, Section 4]), a generalization of Wiener bridge (Pycke [25]), generalized Anderson-Darling process (Pycke [26]), Rodríguez-Viollaz process (Pycke [ 27]), scaled Wiener bridges or also called α-Wiener bridges (Barczy and Iglói [6]), limit processes related to Cramér-von Mises goodness-of-fit tests for hypotheses that an observed diffusion process has a sign-type trend coefficient (Gassem [14]), detrended Wiener processes (Ai, Li and Liu [3]), additive Wiener processes and bridges (Liu [18]), additive Slepian processes (Liu, Huang and Mao [19]), Spartan spatial random fields (Tsantili and Hristopulos [28]), the demeaned stationary Ornstein-Uhlenbeck process (Ai [2]), and the additive two-sided Brownian motion (Ai and Sun [4]). We also mention that KL expansions of Gauss processes have found several applications in small deviation theory, for a complete bibliography, see Lifshits [17]. Here we only mention two papers of Nazarov and Nikitin [20], [22].