“…For instance, based on the approach of [27], Nualart and Rȃşcanu [22] proved the existence and uniqueness result with Hurst parameter H > 1/2; Coutin and Qian [6] also derived the existence and uniqueness result for H ∈ (1/4, 1/2) via the theory of rough path analysis introduced in [18]; in [14,15] and [24], the authors studied the ergodicity and Talagrand's transportation inequalities for the solutions, respectively; Fan [10,11] established Harnack inequalities for the solution with H < 1/2 and H > 1/2, respectively. As for the regularities, the readers may refer to [3,17,20,23] and references therein. However, as far as we know, the study of the existence of density of the solution mainly depends on the Malliavin calculus.…”