$\mathbb{Z}$-graded supergeometry: Differential graded modules, higher algebroid representations, and linear structures

Abstract: This thesis studies the representation theory and linear structures of $\mathcal{Q}$-manifolds and higher Lie algebroids. We introduce differential graded modules (or for short DG-modules) of $\mathcal{Q}$-manifolds and the equivalent notion of representations up to homotopy in the case of Lie $n$-algebroids ($n\in\mathbb{N}$), as generalisations of the homonymous structures that exist already in the case of ordinary Lie algebroids. The adjoint and coadjoint modules are described, and the corresponding split versions of the adjoint and coadjoint representations up to homotopy of Lie $n$-algebroids are explained. The compatibility of a graded Poisson bracket with the homological vector field on a $\mathbb{Z}$-graded manifold is shown to be equivalent to an (anti-)morphism from the coadjoint module to the adjoint module, leading to an alternative characterisation of non-degeneracy of graded Poisson structures. The Weil algebra of a general $\mathcal{Q}$-manifold is defined and is computed explicitly in the case of Lie $n$-algebroids over a base (smooth) manifold $M$ together with a choice of a splitting and linear $TM$-connections. In addition, we study linear structures on $\mathbb{Z}$-graded manifolds, for which we see the connection with DG-modules and representations up to homotopy. In the world of split Lie $n$-algebroids, this leads to the notion of VB-Lie $n$-algebroids. We prove that there is an equivalence between the category of VB-Lie $n$-algebroids over a Lie $n$-algebroid $\underline{A}$ and the category of $(n+1)$-term representations up to homotopy of $\underline{A}$, generalising thus a well-known result from the theory of ordinary VB-algebroids.