Lie submodules of a Lie algebra #
In this file we define Lie submodules, we construct the lattice structure on Lie submodules and we use it to define various important operations, notably the Lie span of a subset of a Lie module.
Main definitions #
LieSubmodule
LieSubmodule.wellFounded_of_noetherian
LieSubmodule.lieSpan
LieSubmodule.map
LieSubmodule.comap
Tags #
lie algebra, lie submodule, lie ideal, lattice structure
A Lie submodule of a Lie module is a submodule that is closed under the Lie bracket. This is a sufficient condition for the subset itself to form a Lie module.
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The zero module is a Lie submodule of any Lie module.
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Copy of a LieSubmodule
with a new carrier
equal to the old one. Useful to fix definitional
equalities.
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Given a Lie subalgebra K ⊆ L
, if we view L
as a K
-module by restriction, it contains
a distinguished Lie submodule for the action of K
, namely K
itself.
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The set of Lie submodules of a Lie module form a complete lattice.
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The natural functor that forgets the action of L
as an order embedding.
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The inclusion of a Lie submodule into its ambient space is a morphism of Lie modules.
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Given two nested Lie submodules N ⊆ N'
,
the inclusion N ↪ N'
is a morphism of Lie modules.
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The lieSpan
of a set s ⊆ M
is the smallest Lie submodule of M
that contains s
.
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lieSpan
forms a Galois insertion with the coercion from LieSubmodule
to Set
.
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An induction principle for span membership. If p
holds for 0 and all elements of s
, and is
preserved under addition, scalar multiplication and the Lie bracket, then p
holds for all
elements of the Lie submodule spanned by s
.
A morphism of Lie modules f : M → M'
pushes forward Lie submodules of M
to Lie submodules
of M'
.
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A morphism of Lie modules f : M → M'
pulls back Lie submodules of M'
to Lie submodules of
M
.
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An injective morphism of Lie modules embeds the lattice of submodules of the domain into that of the target.
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For an injective morphism of Lie modules, any Lie submodule is equivalent to its image.
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An equivalence of Lie modules yields an order-preserving equivalence of their lattices of Lie Submodules.
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The kernel of a morphism of Lie algebras, as an ideal in the domain.
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The range of a morphism of Lie modules f : M → N
is a Lie submodule of N
.
See Note [range copy pattern].
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A morphism of Lie modules f : M → N
whose values lie in a Lie submodule P ⊆ N
can be
restricted to a morphism of Lie modules M → P
.
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The natural equivalence between the 'top' Lie submodule and the enclosing Lie module.
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The natural equivalence between the 'top' Lie subalgebra and the enclosing Lie algebra.
This is the Lie subalgebra version of Submodule.topEquiv
.