Continuously differentiable functions with compact support #
This file develops the basic theory of bundled n-times continuously differentiable functions
with compact support contained in some open set Ξ©. More explicitly, given normed spaces E
and F, an open set Ξ© : Opens E and n : ββ, we are interested in the space π^{n}(Ξ©, F) of
maps f : E β F such that:
fisn-times continuously differentiable:ContDiff β n f.fhas compact support:HasCompactSupport f.- the support of
fis inside the open setΞ©:tsupport f β Ξ©.
This exists as a bundled type to equip it with the canonical LF topology induced by the inclusions
π_{K}^{n}(Ξ©, F) β π^{n}(Ξ©, F) (see ContDiffMapSupportedIn). The dual space is then the space of
distributions, or "weak solutions" to PDEs, on Ξ©.
Main definitions #
TestFunction Ξ© F n: the type of bundledn-times continuously differentiable functionsE β Fwith compact support contained inΞ©.TestFunction.topologicalSpace: the canonical LF topology onπ^{n}(Ξ©, F). It is the locally convex inductive limit of the topologies on eachπ_{K}^{n}(Ξ©, F).
Main statements #
TestFunction.continuous_iff_continuous_comp: a linear map fromπ^{n}(E, F)to a locally convex space is continuous iff its restriction toπ^{n}_{K}(E, F)is continuous for each compact setK. We will later translate this concretely in terms of seminorms.
Notation #
π^{n}(Ξ©, F): the space of bundledn-times continuously differentiable functionsE β Fwith compact support contained inΞ©.π(Ξ©, F): the space of bundled smooth (infinitely differentiable) functionsE β Fwith compact support contained inΞ©, i.e.π^{β€}(Ξ©, F).
Tags #
distributions, test function
The type of bundled n-times continuously differentiable maps with compact support
- toFun : E β F
The underlying function. Use coercion instead.
- hasCompactSupport' : HasCompactSupport self.toFun
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Notation for the space of bundled n-times continuously differentiable maps
with compact support.
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Notation for the space of "test functions", i.e. bundled smooth (infinitely differentiable) maps with compact support.
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TestFunctionClass B Ξ© F n states that B is a type of n-times continuously
differentiable functions E β F with compact support contained in Ξ© : Opens E.
- coe : B β (a : E) β F
- map_hasCompactSupport (f : B) : HasCompactSupport βf
Instances
Equations
- TestFunction.toTestFunctionClass = { coe := fun (f : TestFunction Ξ© F n) => f.toFun, coe_injective' := β―, map_contDiff := β―, map_hasCompactSupport := β―, tsupport_map_subset := β― }
See note [custom simps projection].
Equations
- TestFunction.Simps.coe f = βf
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Copy of a TestFunction with a new toFun equal to the old one. Useful to fix
definitional equalities.
Equations
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Equations
- TestFunction.instAdd = { add := fun (f g : TestFunction Ξ© F n) => { toFun := βf + βg, contDiff' := β―, hasCompactSupport' := β―, tsupport_subset' := β― } }
Equations
- TestFunction.instNeg = { neg := fun (f : TestFunction Ξ© F n) => { toFun := -βf, contDiff' := β―, hasCompactSupport' := β―, tsupport_subset' := β― } }
Equations
- TestFunction.instSub = { sub := fun (f g : TestFunction Ξ© F n) => { toFun := βf - βg, contDiff' := β―, hasCompactSupport' := β―, tsupport_subset' := β― } }
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Coercion as an additive homomorphism.
Equations
- TestFunction.coeFnAddMonoidHom Ξ© F n = { toFun := fun (f : TestFunction Ξ© F n) => βf, map_zero' := β―, map_add' := β― }
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The natural inclusion π^{n}_{K}(E, F) β π^{n}(Ξ©, F) when K β Ξ©.
Equations
- TestFunction.ofSupportedIn K_sub_Ξ© f = { toFun := βf, contDiff' := β―, hasCompactSupport' := β―, tsupport_subset' := β― }
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The "original topology" on π^{n}(Ξ©, F), defined as the supremum over all compacts K β Ξ© of
the topology on π^{n}_{K}(E, F). In other words, this topology makes π^{n}(Ξ©, F) the inductive
limit of the π^{n}_{K}(E, F)s in the category of topological spaces.
Note that this has no reason to be a locally convex (or even vector space) topology. For this
reason, we actually endow π^{n}(Ξ©, F) with another topology, namely the finest locally convex
topology which is coarser than this original topology. See TestFunction.topologicalSpace.
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The canonical LF topology on π^{n}(Ξ©, F). This makes π^{n}(Ξ©, F) the inductive
limit of the π^{n}_{K}(E, F)s in the category of locally convex topological vector spaces
(over β). See TestFunction.continuous_iff_continuous_comp for the corresponding universal
property.
More concretely, this is defined as the infimum of all locally convex topologies which are
coarser than the "original topology" TestFunction.originalTop, which corresponds to taking
the inductive limit in the category of topological spaces.
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Equations
Fix a locally convex topology t on π^{n}(Ξ©, F). t is coarser than the canonical topology
on π^{n}(Ξ©, F) if and only if it is coarser than the "original topology" given by
TestFunction.originalTop.
For every compact K β Ξ©, the inclusion map π^{n}_{K}(E, F) β π^{n}(Ξ©, F) is
continuous. It is in fact a topological embedding, though this fact is not in Mathlib yet.
The natural inclusion π^{n}_{K}(E, F) β π^{n}(Ξ©, F), when K β Ξ©, as a continuous
linear map.
Equations
- TestFunction.ofSupportedInCLM π K_sub_Ξ© = { toFun := fun (f : ContDiffMapSupportedIn E F n K) => TestFunction.ofSupportedIn K_sub_Ξ© f, map_add' := β―, map_smul' := β―, cont := β― }
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Alias of TestFunction.ofSupportedInCLM.
The natural inclusion π^{n}_{K}(E, F) β π^{n}(Ξ©, F), when K β Ξ©, as a continuous
linear map.
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Alias of TestFunction.coe_ofSupportedInCLM.
The universal property of the topology on π^{n}(Ξ©, F): a linear map from
π^{n}(Ξ©, F) to a locally convex topological vector space is continuous if and only if its
precomposition with the inclusion ofSupportedIn K_sub_Ξ© : π^{n}_{K}(E, F) β π^{n}(Ξ©, F) is
continuous for every compact K β Ξ©.
Reformulation of the universal property of the topology on π^{n}(Ξ©, F), in the form of a
custom constructor for continuous linear maps π^{n}(Ξ©, F) βL[π] V, where V is an arbitrary
locally convex topological vector space.
Equations
- TestFunction.mkCLM π toFun map_add map_smul cont = { toFun := toFun, map_add' := map_add, map_smul' := map_smul, cont := β― }
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The inclusion of the space π^{n}(Ξ©, F) into the space E βα΅ F of bounded continuous
functions as a continuous π-linear map.
Equations
- TestFunction.toBoundedContinuousFunctionCLM π = TestFunction.mkCLM π (fun (x : TestFunction Ξ© F n) => { toFun := βx, continuous_toFun := β―, map_bounded' := β― }) β― β― β―
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Given T : F βL[π] F', postcompCLM T is the continuous π-linear-map sending
f : π^{n}(Ξ©, F) to T β f as an element of π^{n}(Ξ©, F').
Equations
- TestFunction.postcompCLM T = TestFunction.mkCLM π (fun (f : TestFunction Ξ© F n) => { toFun := βT β βf, contDiff' := β―, hasCompactSupport' := β―, tsupport_subset' := β― }) β― β― β―