Row-compact maps between modules with property (Pr) #
A module M over a normed ring R has property (Pr) (TauCeti.HasPr R M) if it is a continuous
linear retract M →ⁱ C₀(J, R) →ʳ M, r ∘ i = id, of a model space. A continuous linear map
u : M →L[R] N between two such modules is row compact in the sense of (Pr) modules
(ContinuousLinearMap.IsPrCompact) if for some retract presentations (iM, rM) of M and
(iN, rN) of N the extension iN ∘ u ∘ rM : C₀(J, R) →L[R] C₀(I, R) is row compact
(ContinuousLinearMap.IsRowCompact). This extends row compactness from model spaces to their
continuous linear retracts, without choosing an orthonormal basis of M or N.
Over ultrametric Tate scalars the condition does not depend on the presentations. If
iN ∘ u ∘ rM is row compact and j : N →L[R] C₀(I', R), s : C₀(J', R) →L[R] M are any
continuous linear maps, then j ∘ u ∘ s is the composite (j ∘ rN) ∘ (iN ∘ u ∘ rM) ∘ (iM ∘ s),
which is row compact because row-compact maps form a two-sided operator ideal
(ContinuousLinearMap.isRowCompact_comp_of_retract). No finite-dimensional complement of the
range of iM is presumed.
The ideal, closedness and approximation properties of row-compact maps transport to (Pr)
modules. Over complete ultrametric Tate scalars, let M be a normed module with a bounded scalar
action (IsBoundedSMul). If M is finitely generated with (Pr), every map into M from a module
with (Pr) is row compact. The identity of M is row compact exactly when M has (Pr) and is
finitely generated. Hence a row-compact endomorphism u of M with (1 - u) ^ n = 0 forces M
to be finitely generated projective.
A row-compact idempotent e of a module with (Pr) has finitely generated projective range: through
a retract presentation r ∘ i = id, the inclusion i identifies range e with the range of the
row-compact idempotent i ∘ e ∘ r of the model space
(ContinuousLinearMap.IsRowCompact.projective_range_of_isIdempotentElem).
Main definitions #
ContinuousLinearMap.IsPrCompact: row compactness of a map between modules with property (Pr), through retract presentations.
Main results #
ContinuousLinearMap.IsPrCompact.isRowCompact_comp: for a row-compactu : M →L[R] N, every compositej ∘ u ∘ swith model spaces is row compact; in particular the extension through any presentation is.ContinuousLinearMap.isPrCompact_iff_isRowCompact_comp: independence of the presentation.ContinuousLinearMap.isPrCompact_iff_isRowCompact: on model spaces the notion is row compactness.ContinuousLinearMap.IsPrCompact.comp_clm,ContinuousLinearMap.IsPrCompact.clm_comp,ContinuousLinearMap.isPrCompact_of_tendsto: the closed operator ideal property.ContinuousLinearMap.IsPrCompact.aeval: polynomials with zero constant coefficient preserve row compactness.ContinuousLinearMap.IsPrCompact.tendsto_ringOpNorm_comp_indicatorCLM_comp_sub: a row-compact map is the operator-norm limit of its truncationsrN ∘ π_S ∘ iN ∘ uthrough any presentation of the target.ContinuousLinearMap.IsPrCompact.isCompletelyContinuous: row-compact maps are completely continuous.ContinuousLinearMap.isPrCompact_id_iff: the identity is row compact exactly on finitely generated modules with property (Pr).ContinuousLinearMap.IsPrCompact.projective_of_one_sub_pow_eq_zero: a row-compactuwith(1 - u) ^ n = 0forces the module to be finitely generated projective.ContinuousLinearMap.IsPrCompact.finite_range_of_isIdempotentElem,ContinuousLinearMap.IsPrCompact.projective_range_of_isIdempotentElem: a row-compact idempotent has finitely generated projective range.
References #
- J.-P. Serre, Endomorphismes complètement continus des espaces de Banach p-adiques, Publ. Math. IHÉS 12 (1962), 69–85, §§1–3.
- K. Buzzard, Eigenvarieties, in L-functions and Galois Representations, LMS Lecture Note Series 320 (2007), §2.
- C. Johansson and J. Newton, Extended eigenvarieties for overconvergent cohomology, arXiv:1604.07739, §2.1.
A continuous linear map u : M →L[R] N between modules with property (Pr) is row compact
if there are continuous linear retract presentations rM ∘ iM = id of M through C₀(J, R) and
rN ∘ iN = id of N through C₀(I, R) such that the extension iN ∘ u ∘ rM is row compact.
Over ultrametric Tate scalars this does not depend on the presentations
(ContinuousLinearMap.isPrCompact_iff_isRowCompact_comp). The index types live in the universes
of M and N, as in TauCeti.HasPr.
Instances For
A map is row compact in the sense of (Pr) modules exactly when it has row-compact extensions
through some retract presentations of its source and target. This is the introduction and
elimination interface for ContinuousLinearMap.IsPrCompact.
Retract factorisation: if rM ∘ iM = id and rN ∘ iN = id present the source and target
of u, then u factors through its extension as rN ∘ (iN ∘ u ∘ rM) ∘ iM.
A map whose extension through retract presentations of its source and target is row compact is row compact in the sense of (Pr) modules.
The source of a row-compact map between (Pr) modules has property (Pr).
The target of a row-compact map between (Pr) modules has property (Pr).
The zero map between two modules is row compact exactly when both have property (Pr).
Negatives of row-compact maps between (Pr) modules are row compact.
A negative is row compact between (Pr) modules exactly when the map is.
Over Tate scalars, every map into a retract of a model space with a finite index type is row compact, provided its source has property (Pr).
Scalar multiples of row-compact maps between (Pr) modules are row compact.
Independence of the presentation. Over ultrametric Tate scalars, if the extension
iN ∘ u ∘ rM of u through retract presentations of its source and target is row compact, then
so is every composite j ∘ u ∘ s with continuous linear maps j into and s out of model
spaces: it factors as (j ∘ rN) ∘ (iN ∘ u ∘ rM) ∘ (iM ∘ s).
Over ultrametric Tate scalars, for a row-compact map u between (Pr) modules every composite
j ∘ u ∘ s with continuous linear maps into and out of model spaces is row compact. In
particular the extension of u through any retract presentations is row compact.
Row compactness on (Pr) modules does not depend on the presentation: over ultrametric
Tate scalars, u is row compact exactly when its extension through any one pair of retract
presentations is.
Transport along equivalences with model spaces: over ultrametric Tate scalars, a map
between potentially orthonormalisable modules is row compact exactly when its conjugate
eN ∘ u ∘ eM⁻¹ between the model spaces is.
On model spaces, row compactness in the sense of (Pr) modules is row compactness.
Sums of row-compact maps between (Pr) modules are row compact.
Differences of row-compact maps between (Pr) modules are row compact.
Precomposing a row-compact map between (Pr) modules with a continuous linear map out of a module with property (Pr) gives a row-compact map.
Postcomposing a row-compact map between (Pr) modules with a continuous linear map into a module with property (Pr) gives a row-compact map.
A polynomial with zero constant coefficient preserves row compactness on modules with property (Pr), over ultrametric Tate scalars.
Closedness: over ultrametric Tate scalars, an operator-norm limit of row-compact maps between (Pr) modules is row compact.
Approximation by truncations: over ultrametric Tate scalars, if rN ∘ iN = id presents
the target of a row-compact map u between (Pr) modules, then the truncations
rN ∘ π_S ∘ iN ∘ u converge to u in operator norm as the finite set S of coordinates grows.
Here π_S = ZeroAtInftyContinuousMap.indicatorCLM R S is the coordinate projection.
Over ultrametric Tate scalars, row-compact maps between (Pr) modules are completely continuous.
Over complete ultrametric Tate scalars, every continuous linear map from a module with
property (Pr) into a finitely generated module with property (Pr) is row compact. A finitely
generated module with (Pr) is a retract of C₀(S, R) for a finite set S of generators.
The identity criterion on (Pr) modules: over complete ultrametric Tate scalars, the identity of a module is row compact exactly when the module has property (Pr) and is finitely generated.
The finiteness germ: over complete ultrametric Tate scalars, a row-compact endomorphism
u of a (Pr) module with (1 - u) ^ n = 0 forces the module to be finitely generated.
Over complete ultrametric Tate scalars, a row-compact endomorphism u of a (Pr) module with
(1 - u) ^ n = 0 forces the module to be finitely generated projective.
A row-compact idempotent of a (Pr) module has finitely generated range.
A row-compact idempotent of a (Pr) module has projective range.