We introduce a notion of L-dendriform algebra due to several different
motivations. L-dendriform algebras are regarded as the underlying algebraic
structures of pseudo-Hessian structures on Lie groups and the algebraic
structures behind the $\mathcal O$-operators of pre-Lie algebras and the
related $S$-equation. As a direct consequence, they provide some explicit
solutions of $S$-equation in certain pre-Lie algebras constructed from
L-dendriform algebras. They also fit into a bigger framework as Lie algebraic
analogues of dendriform algebras. Moreover, we introduce a notion of $\mathcal
O$-operator of an L-dendriform algebra which gives an algebraic equation
regarded as an analogue of the classical Yang-Baxter equation in a Lie algebra.Comment: 15 page