In this paper, we are interested in the following one dimensional forward stochastic differential equation (SDE)where the driving noise Bt is a d-dimensional Brownian motion. The drift coefficient b : [0, T ] × Ω × R −→ R is Borel measurable and can be decomposed into a deterministic and a random part, i.e., b(t, x, ω) = b1(t, x) + b2 (t, x, ω). Assuming that b1 is of spacial linear growth and b2 satisfies some integrability conditions, we obtain the existence and uniqueness of a strong solution. The method we use is purely probabilitic and relies on Malliavin calculus. As byproducts, we obtain Malliavin differentiability of the solutions, provide an explicit representation for the Malliavin derivative and prove existence of weighted Sobolev differentiable flows.
KEYWORDS:Malliavin calculus, random drift, measurable drift, compactness criterion, explicit representation, Sobolev differentiable flow. MSC 2010: 60G15, 60G60, 60H07, 60H10 * We thank an associate editor and the anonymous referees for their feedback and suggestions, one of which led to Theorem 1.3. We also thank Daniel Ocone for his comments.
Probabilistic settingLet T ∈ (0, ∞) and d ∈ N be fixed and consider a probability space (Ω, F , P ) equipped with the completed filtration (F t ) t∈[0,T ] of a d-dimensional Brownian motion B. Throughout the paper, the product Ω × [0, T ] is endowed with the predictable σ-algebra. Subsets of R k , k ∈ N, are always endowed with the Borel σ-algebra induced by the Euclidean norm | · |. The interval [0, T ] is equipped with the Lebesgue measure. Unless otherwise stated, all equalities and inequalities