Projective seminorm on the tensor of a finite family of normed spaces. #
Let ๐ be a normed field and E be a family of normed ๐-vector spaces Eแตข,
indexed by a finite type ฮน. We define a seminorm on โจ[๐] i, Eแตข, which we call the
"projective seminorm". For x an element of โจ[๐] i, Eแตข, its projective seminorm is the
infimum over all expressions of x as โ j, โจโ[๐] mโฑผ i (with the mโฑผ โ ฮ i, Eแตข)
of โ j, ฮ i, โmโฑผ iโ.
In particular, every norm โ.โ on โจ[๐] i, Eแตข satisfying โโจโ[๐] i, m iโ โค ฮ i, โm iโ
for every m in ฮ i, Eแตข is bounded above by the projective seminorm.
Main definitions #
PiTensorProduct.projectiveSeminorm: The projective seminorm onโจ[๐] i, Eแตข.PiTensorProduct.liftEquiv: The bijection betweenContinuousMultilinearMap ๐ E Fand(โจ[๐] i, Eแตข) โL[๐] F, as a continuous linear equivalence.PiTensorProduct.liftIsometry: The bijection betweenContinuousMultilinearMap ๐ E Fand(โจ[๐] i, Eแตข) โL[๐] F, as an isometric linear equivalence.PiTensorProduct.tprodL: The canonical continuous multilinear map fromE = ฮ แตข Eแตขtoโจ[๐] i, Eแตข.PiTensorProduct.mapL: The continuous linear map fromโจ[๐] i, Eแตขtoโจ[๐] i, E'แตขinduced by a family of continuous linear mapsEแตข โL[๐] E'แตข.PiTensorProduct.mapLMultilinear: The continuous multilinear map fromฮ แตข (Eแตข โL[๐] E'แตข)to(โจ[๐] i, Eแตข) โL[๐] (โจ[๐] i, E'แตข)sending a familyftoPiTensorProduct.mapL f.
Main results #
PiTensorProduct.norm_eval_le_projectiveSeminorm: Iffis a continuous multilinear map onE = ฮ i, Eแตขandxis inโจ[๐] i, Eแตข, thenโf.lift xโ โค projectiveSeminorm x * โfโ.PiTensorProduct.mapL_opNorm: Iffis a family of continuous linear mapsfแตข : Eแตข โL[๐] Fแตข, thenโPiTensorProduct.mapL fโ โค โ i, โfแตขโ.PiTensorProduct.opNorm_mapLMultilinear_le: IfFis a normed vecteor space, thenโmapLMultilinear ๐ E Fโ โค 1.
TODO #
- If the base field is
โorโ(or more generally if the injection ofEแตขinto its bidual is an isometry for everyi), then we haveprojectiveSeminorm โจโ[๐] i, mแตข = ฮ i, โmแตขโ. - If all
Eแตขare separated and satisfySeparatingDual, then the seminorm onโจ[๐] i, Eแตขis a norm. - Adapt the remaining functoriality constructions/properties from
PiTensorProduct.
A lift of the projective seminorm to FreeAddMonoid (๐ ร ฮ i, Eแตข), useful to prove the
properties of projectiveSeminorm.
Equations
Instances For
Equations
- PiTensorProduct.instNorm = { norm := fun (x : PiTensorProduct ๐ fun (i : ฮน) => E i) => โจ (p : โx.lifts), PiTensorProduct.projectiveSeminormAux โp }
The projective seminorm on โจ[๐] i, Eแตข. It sends an element x of โจ[๐] i, Eแตข to the
infimum over all expressions of x as โ j, โจโ[๐] mโฑผ i (with the mโฑผ โ ฮ i, Eแตข)
of โ j, ฮ i, โmโฑผ iโ.
Equations
- PiTensorProduct.projectiveSeminorm = Seminorm.ofSMulLE norm โฏ โฏ โฏ
Instances For
Equations
- One or more equations did not get rendered due to their size.
Equations
- PiTensorProduct.instNormedSpace = { toModule := PiTensorProduct.instModule, norm_smul_le := โฏ }
The linear equivalence between ContinuousMultilinearMap ๐ E F and (โจ[๐] i, Eแตข) โL[๐] F
induced by PiTensorProduct.lift, for every normed space F.
Equations
- One or more equations did not get rendered due to their size.
Instances For
For a normed space F, we have constructed in PiTensorProduct.liftEquiv the canonical
linear equivalence between ContinuousMultilinearMap ๐ E F and (โจ[๐] i, Eแตข) โL[๐] F
(induced by PiTensorProduct.lift). Here we give the upgrade of this equivalence to
an isometric linear equivalence; in particular, it is a continuous linear equivalence.
Equations
- PiTensorProduct.liftIsometry ๐ E F = LinearIsometryEquiv.ofBounds (PiTensorProduct.liftEquiv ๐ E F) โฏ โฏ
Instances For
The canonical continuous multilinear map from E = ฮ แตข Eแตข to โจ[๐] i, Eแตข.
Equations
- PiTensorProduct.tprodL ๐ = (PiTensorProduct.liftIsometry ๐ E (PiTensorProduct ๐ fun (i : ฮน) => E i)).symm (ContinuousLinearMap.id ๐ (PiTensorProduct ๐ fun (i : ฮน) => E i))
Instances For
Let Eแตข and E'แตข be two families of normed ๐-vector spaces.
Let f be a family of continuous ๐-linear maps between Eแตข and E'แตข, i.e.
f : ฮ แตข Eแตข โL[๐] E'แตข, then there is an induced continuous linear map
โจแตข Eแตข โ โจแตข E'แตข by โจ aแตข โฆ โจ fแตข aแตข.
Equations
- PiTensorProduct.mapL f = (PiTensorProduct.liftIsometry ๐ E (PiTensorProduct ๐ fun (i : ฮน) => E' i)) ((PiTensorProduct.tprodL ๐).compContinuousLinearMap f)
Instances For
Given submodules pแตข โ Eแตข, this is the natural map: โจ[๐] i, pแตข โ โจ[๐] i, Eแตข.
This is the continuous version of PiTensorProduct.mapIncl.
Equations
- PiTensorProduct.mapLIncl p = PiTensorProduct.mapL fun (i : ฮน) => (p i).subtypeL
Instances For
Upgrading PiTensorProduct.mapL to a MonoidHom when E = E'.
Equations
- PiTensorProduct.mapLMonoidHom = { toFun := PiTensorProduct.mapL, map_one' := โฏ, map_mul' := โฏ }
Instances For
The tensor of a family of linear maps from Eแตข to E'แตข, as a continuous multilinear map of
the family.
Equations
- PiTensorProduct.mapLMultilinear ๐ E E' = { toFun := PiTensorProduct.mapL, map_update_add' := โฏ, map_update_smul' := โฏ }.mkContinuous 1 โฏ