Solution to SDE

Theorem (Solution to SDE)

Let (Zt)t≥0(Z_{t})_{t\ge 0} be Rr\mathbb{R}^{r}-valued continuous semimartingale and let F:R+×Rd→Md,r(R)F:\mathbb{R}^{+}\times \mathbb{R}^{d}\to\mathscr{M}_{d,r}(\mathbb{R}) be s.t. ∃k>0\exists k>0 s.t. ∥F(t,x)−F(t,x′)∥≤K∥x−x′∥∀t∈R+,∀x,x′∈Rd\lVert F(t,x)-F(t,x') \rVert \le K\lVert x-x' \rVert \quad\forall t\in\mathbb{R}^{+},\forall x,x'\in\mathbb{R}^{d}and t↦F(t,x)t\mapsto F(t,x) is locally bounded ∀x∈Rd\forall x\in\mathbb{R}^{d}. Consider the SDE dXt=F(t,Xt)dZt,X0=x∈Rd(*)\tag{*}dX_{t}=F(t,X_{t})dZ_{t},\quad X_{0}=x\in\mathbb{R}^{d}Assume the filtration (Ft)t≥0(\mathcal{F}_{t})_{t\ge 0} satisfies the Usual conditions. Then: ∀x∈R\forall x\in\mathbb{R}, ∃!\exists ! up to indistinguishability a continuous (FtZ)t≥0(\mathcal{F}_{t}^{Z})_{t\ge 0}-adapted process (Xt)t≥0(X_{t})_{t\ge 0} satisfying (∗)(*).