English
TwoCochain R L M is the submodule of linear maps c ∈ L →ₗ[R] (L →ₗ[R] M) such that ∀ x ∈ L, c x x = 0.
Русский
TwoCochain — подмодуль линейных отображений c ∈ L →ₗ[R] (L →ₗ[R] M) с условием ∀ x, c x x = 0.
LaTeX
$$$ twoCochain: = \{ c \in L →ₗ[R] (L →ₗ[R] M) \mid ∀ x, c(x)(x) = 0 \} $$$
Lean4
/-- Lie algebra 2-cochains over `L` with coefficients in the module `M`. -/
def twoCochain : Submodule R (L →ₗ[R] L →ₗ[R] M)
where
carrier := {c | ∀ x, c x x = 0}
add_mem' {a b} ha hb x := by simp [ha x, hb x]
zero_mem' := by simp
smul_mem' t {c} hc x := by simp [hc x]