Compact operators and nonarchimedean Fredholm theory

The declarations the status of Tau Ceti's roadmap names, and the other results named in the modules where only this status names declarations, or in folders below the areas where only it names 2 or more, as Tau Ceti has them at commit ace60277.

TheoremSerre's criterion over a field#

over a complete ultrametric nontrivially normed field K, a continuous linear map between model spaces is row compact exactly when it is completely continuous. Neither a discrete valuation nor spherical completeness is needed.

ContinuousLinearMap.isRowCompact_iff_isCompletelyContinuous.{u_1, u_2, u_4} {I : Type u_1}
  {J : Type u_2} [TopologicalSpace I] [DiscreteTopology I] [TopologicalSpace J] [DiscreteTopology J]
  [DecidableEq J] {K : Type u_4} [NontriviallyNormedField K] [IsUltrametricDist K] [CompleteSpace K]
  {u : ZeroAtInftyContinuousMap J K →L[K] ZeroAtInftyContinuousMap I K} :
  u.IsRowCompact ↔ u.IsCompletelyContinuous
Lean

Formalized in Tau Ceti as ContinuousLinearMap.isRowCompact_iff_isCompletelyContinuous.

Other forms

Serre's criterion. Formalized in Tau Ceti as ContinuousLinearMap.IsCompletelyContinuous.isRowCompact_of_forall_fg_isClosed.

ContinuousLinearMap.IsCompletelyContinuous.isRowCompact_of_forall_fg_isClosed.{u_1, u_2, u_3}
  {I : Type u_1} {J : Type u_2} {R : Type u_3} [TopologicalSpace I] [DiscreteTopology I]
  [TopologicalSpace J] [DiscreteTopology J] [DecidableEq J] [NormedRing R] [IsUltrametricDist R]
  [CompleteSpace R] [TauCeti.NormedRing.IsTate R]
  {u : ZeroAtInftyContinuousMap J R →L[R] ZeroAtInftyContinuousMap I R}
  (hu : u.IsCompletelyContinuous)
  (hclosed : ∀ (L : Submodule R (ZeroAtInftyContinuousMap I R)), L.FG → IsClosed ↑L) :
  u.IsRowCompact

Serre's criterion for diagonal operators. Formalized in Tau Ceti as ZeroAtInftyContinuousMap.isCompletelyContinuous_diagonalCLM_iff.

ZeroAtInftyContinuousMap.isCompletelyContinuous_diagonalCLM_iff.{u_1, u_3} {I : Type u_1}
  [TopologicalSpace I] [DiscreteTopology I] {K : Type u_3} [NontriviallyNormedField K]
  [IsUltrametricDist K] [CompleteSpace K] {d : BoundedContinuousFunction I K} :
  (ZeroAtInftyContinuousMap.diagonalCLM d).IsCompletelyContinuous ↔
    Filter.Tendsto (⇑d) Filter.cofinite (nhds 0)

Serre's criterion for orthonormalisability. Formalized in Tau Ceti as TauCeti.isONable_iff_free_residueModule.

TauCeti.isONable_iff_free_residueModule.{u_4, u} {R : Type u_4} [NormedCommRing R]
  [IsUltrametricDist R] [NormOneClass R] [CompleteSpace R] {M : Type u} [NormedAddCommGroup M]
  [IsUltrametricDist M] [_root_.Module R M] [IsBoundedSMul R M] [CompleteSpace M]
  (ϖ : TauCeti.NormedRing.PseudoUniformizer R)
  (hR : ∀ (a : R), TauCeti.zpowCeil ‖↑ϖ.unit‖ ‖a‖ = ‖a‖)
  (hM : ∀ (m : M), TauCeti.zpowCeil ‖↑ϖ.unit‖ ‖m‖ = ‖m‖) :
  TauCeti.IsONable R M ↔
    Module.Free (↥(Subring.unitClosedBall R) ⧸ TauCeti.unitBallIdeal R) (TauCeti.ResidueModule R M)
Sources
Uses 3 · Used by 1

TheoremRow compactness is compactoid image#

over an ultrametric nontrivially normed field, a map between model spaces is row compact exactly when it maps the closed unit ball to a compactoid set.

ContinuousLinearMap.isRowCompact_iff_hasCompactoidImage.{u_1, u_2, u_3} {I : Type u_1}
  {J : Type u_2} {K : Type u_3} [TopologicalSpace I] [DiscreteTopology I] [TopologicalSpace J]
  [DiscreteTopology J] [DecidableEq J] [NontriviallyNormedField K] [IsUltrametricDist K]
  {u : ZeroAtInftyContinuousMap J K →L[K] ZeroAtInftyContinuousMap I K} :
  u.IsRowCompact ↔ u.HasCompactoidImage
Uses 1

TheoremThe Fredholm determinant is entire#

For a row-compact u, the principal-minor series det (1 - T u) is a restricted power series at every radius.

ContinuousLinearMap.IsRowCompact.isEntire_charPowerSeries.{u_1, u_2} {I : Type u_1} {R : Type u_2}
  [TopologicalSpace I] [DiscreteTopology I] [DecidableEq I] [NormedCommRing R] [NormOneClass R]
  [IsUltrametricDist R] {u : ZeroAtInftyContinuousMap I R →L[R] ZeroAtInftyContinuousMap I R}
  (hu : u.IsRowCompact) : u.matrixCoeff.charPowerSeries.IsEntire
Uses 1 · Used by 5

TheoremInvertibility and the Fredholm series#

For a row-compact endomorphism u of C₀(I, R), the operator 1 - a • u is invertible if and only if the value H_u(a) of the Fredholm series det (1 - T u) is a unit of R.

ContinuousLinearMap.IsRowCompact.isUnit_one_sub_smul_iff.{u_1, u_2} {I : Type u_1}
  [TopologicalSpace I] [DiscreteTopology I] [DecidableEq I] {R : Type u_2} [NormedCommRing R]
  [IsUltrametricDist R] [CompleteSpace R] [TauCeti.NormedRing.IsTate R]
  {u : ZeroAtInftyContinuousMap I R →L[R] ZeroAtInftyContinuousMap I R} (hu : u.IsRowCompact)
  {a : R} : IsUnit (1 - a • u) ↔ IsUnit (u.matrixCoeff.charPowerSeries.evalAt a)
Uses 2

TheoremThe nonzero spectrum of a row-compact operator#

For a row-compact endomorphism u of C₀(I, K) over a complete ultrametric field and μ ≠ 0, μ lies in the spectrum of u if and only if μ⁻¹ is a zero of the Fredholm series det (1 - T u).

ContinuousLinearMap.IsRowCompact.mem_spectrum_iff_evalAt_inv_eq_zero.{u_1, u_2} {I : Type u_1}
  [TopologicalSpace I] [DiscreteTopology I] [DecidableEq I] {K : Type u_2}
  [NontriviallyNormedField K] [IsUltrametricDist K] [CompleteSpace K]
  {u : ZeroAtInftyContinuousMap I K →L[K] ZeroAtInftyContinuousMap I K} (hu : u.IsRowCompact)
  {μ : K} (hμ : μ ≠ 0) : μ ∈ spectrum K u ↔ u.matrixCoeff.charPowerSeries.evalAt μ⁻¹ = 0
Uses 4 · Used by 1

TheoremContinuousLinearMap.IsCompletelyContinuous.isFredholm_one_sub#

A completely continuous perturbation of the identity is a Fredholm operator, over any complete nontrivially normed field.

ContinuousLinearMap.IsCompletelyContinuous.isFredholm_one_sub.{u_1, u_2} {K : Type u_1}
  {E : Type u_2} [NontriviallyNormedField K] [CompleteSpace K] [NormedAddCommGroup E]
  [NormedSpace K E] [CompleteSpace E] {u : E →L[K] E} (hu : u.IsCompletelyContinuous) :
  (1 - u).IsFredholm
Used by 1

TheoremContinuousLinearMap.IsRowCompact.evalAt_charPowerSeries_eq_zero_iff_hasEigenvalue#

The zeros of the Fredholm series of a row-compact operator are exactly the inverses of its nonzero eigenvalues. This conclusion concerns eigenvalues in the given coefficient field.

ContinuousLinearMap.IsRowCompact.evalAt_charPowerSeries_eq_zero_iff_hasEigenvalue.{u_1, u_2}
  {K : Type u_1} {I : Type u_2} [NontriviallyNormedField K] [CompleteSpace K] [IsUltrametricDist K]
  [TopologicalSpace I] [DiscreteTopology I] [DecidableEq I]
  {u : ZeroAtInftyContinuousMap I K →L[K] ZeroAtInftyContinuousMap I K} (hu : u.IsRowCompact)
  {a : K} : u.matrixCoeff.charPowerSeries.evalAt a = 0 ↔ a ≠ 0 ∧ Module.End.HasEigenvalue (↑u) a⁻¹
Uses 5

TheoremThe Riesz projector at a good zero#

Let u be row compact, and let a be a good zero of order h of its Fredholm determinant H_u: ΔʲH_u(a) = 0 for j < h and ΔʰH_u(a) is a unit. Then 1 - (C b) ^ h is a Riesz projection of u at a of order h.

ContinuousLinearMap.IsRowCompact.isRieszProjection_rieszProjection.{u_1, u_2} {I : Type u_1}
  {R : Type u_2} [TopologicalSpace I] [NormedCommRing R] [TauCeti.NormedRing.IsTate R]
  [DiscreteTopology I] [DecidableEq I] [IsUltrametricDist R] [CompleteSpace R]
  {u : ZeroAtInftyContinuousMap I R →L[R] ZeroAtInftyContinuousMap I R} (hu : u.IsRowCompact)
  {a : R} {h : ℕ}
  (hH : ∀ j < h, ((PowerSeries.hasseDeriv j) u.matrixCoeff.charPowerSeries).evalAt a = 0)
  (hc : IsUnit (((PowerSeries.hasseDeriv h) u.matrixCoeff.charPowerSeries).evalAt a)) :
  u.IsRieszProjection a h (u.rieszProjection a h)
Uses 2

DefinitionContinuousLinearMap.IsRowCompact#

A continuous linear map between model spaces is row compact if the entries of its matrix are uniformly bounded and its row norms tend to zero along the cofinite filter of output indices. The bound is automatic over Tate scalars (ContinuousLinearMap.isRowCompact_iff_tendsto_rowNorm); it is part of the definition so that the real suprema defining the row norms are meaningful.

ContinuousLinearMap.IsRowCompact.{u_1, u_2, u_5} {I : Type u_1} {J : Type u_2} {R : Type u_5}
  [TopologicalSpace I] [TopologicalSpace J] [DiscreteTopology J] [DecidableEq J] [SeminormedRing R]
  (u : ZeroAtInftyContinuousMap J R →L[R] ZeroAtInftyContinuousMap I R) : Prop
Used by 12

TheoremA row-compact idempotent has projective range#

ContinuousLinearMap.IsRowCompact.projective_range_of_isIdempotentElem.{u_1, u_2} {I : Type u_1}
  {R : Type u_2} [TopologicalSpace I] [DiscreteTopology I] [DecidableEq I] [NormedRing R]
  [IsUltrametricDist R] [TauCeti.NormedRing.IsTate R] [CompleteSpace R]
  {e : ZeroAtInftyContinuousMap I R →L[R] ZeroAtInftyContinuousMap I R} (hu : e.IsRowCompact)
  (he : IsIdempotentElem e) : Module.Projective R ↥(↑e).range
Uses 1

DefinitionContinuousLinearMap.charPowerSeries#

The Fredholm series det (1 - T u) of an endomorphism u of a module M with property (Pr): the principal-minor series of the extension i ∘ u ∘ r of u through a retract presentation r ∘ i = id of M by a model space C₀(J, R), fixed by choice. If u is row compact, it does not depend on the presentation (ContinuousLinearMap.IsPrCompact.charPowerSeries_eq). If M does not have property (Pr) the series is 1.

ContinuousLinearMap.charPowerSeries.{u, w} {R : Type w} [SeminormedCommRing R] {M : Type u}
  [SeminormedAddCommGroup M] [_root_.Module R M] (u : M →L[R] M) : PowerSeries R
Used by 3

TheoremIndependence of the presentation#

The Fredholm series of a row-compact endomorphism u of a module with property (Pr) is the principal-minor series of its extension i ∘ u ∘ r through any retract presentation r ∘ i = id of the module by a model space.

ContinuousLinearMap.IsPrCompact.charPowerSeries_eq.{u, w, u_1} {R : Type w} [NormedCommRing R]
  [NormOneClass R] [IsUltrametricDist R] [CompleteSpace R] [TauCeti.NormedRing.IsTate R]
  {M : Type u} [SeminormedAddCommGroup M] [_root_.Module R M] {u : M →L[R] M} (hu : u.IsPrCompact)
  {J : Type u_1} [TopologicalSpace J] [DiscreteTopology J] [DecidableEq J]
  {i : M →L[R] ZeroAtInftyContinuousMap J R} {r : ZeroAtInftyContinuousMap J R →L[R] M}
  (hri : r ∘SL i = ContinuousLinearMap.id R M) :
  u.charPowerSeries = (i ∘SL u ∘SL r).matrixCoeff.charPowerSeries
Uses 2 · Used by 2

DefinitionPowerSeries.IsGoodZero#

A power series f has a good zero of order h at a if its Hasse derivatives of order less than h vanish at a and its Hasse derivative of order h is a unit at a. For h = 0 this says that f(a) is a unit. Values at a are the infinite sums PowerSeries.evalAt, so the notion is meaningful for entire series over a complete normed ring.

PowerSeries.IsGoodZero.{u_1} {R : Type u_1} [CommRing R] [TopologicalSpace R] (f : PowerSeries R)
  (a : R) (h : ℕ) : Prop

TheoremThe Riesz identity at a good zero#

Let u be row compact, put C = 1 - a • u, and suppose ΔʲH_u(a) = 0 for j < h while c = ΔʰH_u(a) is a unit, so that a is a good zero of order h of the Fredholm determinant. Then b = c⁻¹ • ΔʰV(a) satisfies C ^ (h + 1) b = C ^ h, that is, C ^ h (C b - 1) = 0. This is the identity from which the Riesz projector 1 - (C b) ^ h at a and its complementary projector (C b) ^ h are built.

ContinuousLinearMap.IsRowCompact.one_sub_smul_pow_succ_mul_inverse_smul_resolventHasseDerivAt.{u_1,
    u_2}
  {I : Type u_1} {R : Type u_2} [TopologicalSpace I] [DiscreteTopology I] [DecidableEq I]
  [NormedCommRing R] [TauCeti.NormedRing.IsTate R] [IsUltrametricDist R] [CompleteSpace R]
  {u : ZeroAtInftyContinuousMap I R →L[R] ZeroAtInftyContinuousMap I R} (hu : u.IsRowCompact)
  {a : R} {h : ℕ}
  (hH : ∀ j < h, ((PowerSeries.hasseDeriv j) u.matrixCoeff.charPowerSeries).evalAt a = 0)
  (hc : IsUnit (((PowerSeries.hasseDeriv h) u.matrixCoeff.charPowerSeries).evalAt a)) :
  (1 - a • u) ^ (h + 1) *
      Ring.inverse (((PowerSeries.hasseDeriv h) u.matrixCoeff.charPowerSeries).evalAt a) •
        u.resolventHasseDerivAt h a =
    (1 - a • u) ^ h
Uses 2 · Used by 1

TheoremRow Hodge lower bound for a row-compact operator#

Let v be a real additive valuation on an ultrametric normed field with ‖x‖ = b ^ (-v x) for x ≠ 0, where b > 1. For a row-compact endomorphism u of C₀(I, K), the row Hodge polygon of its row norms lies below the Newton polygon of its principal-minor series u.matrixCoeff.charPowerSeries. When K is complete, these principal-minor sums converge and the series is the Fredholm series det (1 - T u).

ContinuousLinearMap.IsRowCompact.rowHodgePolygon_rowNorm_le_newtonPolygon_charPowerSeries.{u_1, u_2}
  {I : Type u_1} {K : Type u_2} [TopologicalSpace I] [DiscreteTopology I] [DecidableEq I] {b : ℝ}
  [NormedField K] [IsUltrametricDist K] {v : AddValuation K (WithTop ℝ)}
  {u : ZeroAtInftyContinuousMap I K →L[K] ZeroAtInftyContinuousMap I K} (hu : u.IsRowCompact)
  (hb : 1 < b) (hv : ∀ (x : K), x ≠ 0 → ‖x‖ = b ^ (-(v x).untop₀)) :
  TauCeti.rowHodgePolygon b u.rowNorm ≤ u.matrixCoeff.charPowerSeries.newtonPolygon v
Uses 2

TheoremStrassmann's bound for the spectrum#

Let u be a row-compact endomorphism of C₀(I, K), and let its Fredholm series H_u be distinguished of degree s at the radius ε⁻¹. Then the extension of u to C₀(I, L), for a complete normed field extension L of K, has at most s spectral values of norm at least ε.

ContinuousLinearMap.IsRowCompact.encard_setOf_mem_spectrum_mapCoeffs_le.{u_1, u_2, u_3}
  {I : Type u_1} [TopologicalSpace I] [DiscreteTopology I] [DecidableEq I] {K : Type u_2}
  {L : Type u_3} [NontriviallyNormedField K] [IsUltrametricDist K] [CompleteSpace K]
  [NontriviallyNormedField L] [NormedAlgebra K L] [IsUltrametricDist L] [CompleteSpace L]
  {u : ZeroAtInftyContinuousMap I K →L[K] ZeroAtInftyContinuousMap I K} (hu : u.IsRowCompact)
  {ε : ℝ} (hε : 0 < ε) {s : ℕ}
  (hs : TauCeti.PowerSeries.IsDistinguished ε⁻¹ s u.matrixCoeff.charPowerSeries) :
  {μ | μ ∈ spectrum L (u.mapCoeffs (algebraMap K L) ⋯) ∧ ε ≤ ‖μ‖}.encard ≤ ↑s
Lean

Formalized in Tau Ceti as ContinuousLinearMap.IsRowCompact.encard_setOf_mem_spectrum_mapCoeffs_le.

Other forms

Strassmann's bound for the spectrum over the coefficient field. Formalized in Tau Ceti as ContinuousLinearMap.IsRowCompact.encard_setOf_mem_spectrum_le.

ContinuousLinearMap.IsRowCompact.encard_setOf_mem_spectrum_le.{u_1, u_2} {I : Type u_1}
  [TopologicalSpace I] [DiscreteTopology I] [DecidableEq I] {K : Type u_2}
  [NontriviallyNormedField K] [IsUltrametricDist K] [CompleteSpace K]
  {u : ZeroAtInftyContinuousMap I K →L[K] ZeroAtInftyContinuousMap I K} (hu : u.IsRowCompact)
  {ε : ℝ} (hε : 0 < ε) {s : ℕ}
  (hs : TauCeti.PowerSeries.IsDistinguished ε⁻¹ s u.matrixCoeff.charPowerSeries) :
  {μ | μ ∈ spectrum K u ∧ ε ≤ ‖μ‖}.encard ≤ ↑s
Sources
Uses 4

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