Formal deformations, cohomology theory and L₁-structures for differential Lie algebras of arbitrary weight

Generalising a previous work of Jiang and Sheng, a cohomology theory for differential Lie algebras of arbitrary weight is introduced. The underlying L₁-structure on the cochain complex is also determined via a generalised version of higher derived brackets. The equivalence between L₁-structures for absolute and relative differential Lie algebras are established. Formal deformations and abelian extensions are interpreted by using lower degree cohomology groups. Also we introduce the homotopy differential Lie algebras. In a forthcoming paper, we will show that the operad of homotopy (relative) differential Lie algebras is the minimal model of the operad of (relative) differential Lie algebras.