Cyclic forms on DG-Lie algebroids and semiregularity

Abstract: Given a transitive DG-Lie algebroid $(\mathcal{A}, \rho)$ over a smooth separated scheme $X$ of finite type over a field $\mathbb{K}$ of characteristic $0$ we define a notion of connection $\nabla \colon \mathbf{R}\Gamma(X,\mathrm{Ker} \rho) \to \mathbf{R}\Gamma (X,\Omega_X^1[-1]\otimes \mathrm{Ker} \rho)$ and construct an $L_\infty$ morphism between DG-Lie algebras $f \colon \mathbf{R}\Gamma(X, \mathrm{Ker} \rho) \rightsquigarrow\mathbf{R}\Gamma(X, \Omega_X^{\leq 1} [2])$ associated to a connection and to a cyclic form on the DG-Lie algebroid. In this way, we obtain a lifting of the first component of the modified Buchweitz-Flenner semiregularity map in the algebraic context, which has an application to the deformation theory of coherent sheaves on $X$ admitting a finite locally free resolution. Another application is to the deformations of (Zariski) principal bundles on $X$.