diff --git a/trees/fcap-000T.tree b/trees/fcap-000T.tree index ad5cff18..d8faf7a7 100644 --- a/trees/fcap-000T.tree +++ b/trees/fcap-000T.tree @@ -8,6 +8,6 @@ \taxon{Remark} \title{Infinitesimal and global Clifford symmetry} -\p{The quadratic Clifford Lie algebra is the infinitesimal part of the same conjugation action that produces reflections. Kostant proves that #{\bigwedge^2V=\operatorname{Lie}(\Spin(V))}, that its map to #{\mathfrak{so}(V)} is the differential of #{\Spin(V)\to SO(V)}, and that its commutator action extends as the corresponding derivation of the exterior algebra \citet{Section 2.4, Theorem 8, pp. 286--287}{kostant1997clifford}. Chevalley obtains the same two-vector Lie algebra inside the Clifford group \citet{II.2.9, pp. 67--68}{chevalley1954algebraic}.} +\p{The quadratic Clifford Lie algebra is the infinitesimal part of the same conjugation action that produces reflections. Kostant proves that #{\bigwedge^2V=\operatorname{Lie}(\Spin(V))}, that its map to #{\mathfrak{so}(V)} is the differential of #{\Spin(V)\to SO(V)}, and that its commutator action extends as the corresponding derivation of the exterior algebra \citet{Section 2.4, Theorem 8, pp. 286--287}{kostant1997clifford}. Chevalley obtains the same two-vector Lie algebra inside the Clifford group \citet{Chapter II, Section 2.9, pp. 67--68}{chevalley1954algebraic}.} -\p{The cards above identify the algebraic Lie layer. They do not construct Lie-group structures or identify a differential of a Lie-group covering map. The next chapter instead reaches the global orthogonal group by finite products of reflections.} +\p{The results above identify the relevant Lie algebras. Constructing the Lie-group structures and identifying the differential of a covering homomorphism require additional arguments. The next chapter reaches the orthogonal group by finite products of reflections.} diff --git a/trees/fcap-0010.tree b/trees/fcap-0010.tree index 6011cc51..705bb737 100644 --- a/trees/fcap-0010.tree +++ b/trees/fcap-0010.tree @@ -11,8 +11,8 @@ that plane tensors the Clifford algebra with two-by-two real matrices. Iteration removes the common part of a real signature, while a sign switch gives a complementary one-sided recurrence. These are algebraic steps toward -the real classification; the real Pin and Spin groups follow a separate -branch through the double-cover theory.} +the real classification. The real Pin and Spin groups are instead constructed +using the double-cover theory.} \related{\ref{ca-0001}} diff --git a/trees/fcap-0011.tree b/trees/fcap-0011.tree index 79590b1c..033627c9 100644 --- a/trees/fcap-0011.tree +++ b/trees/fcap-0011.tree @@ -6,7 +6,7 @@ \tag{clifford} \taxon{Convention} -\title{Real signature and Clifford signs \citet{II.2.9, pp. 65--66}{chevalley1954algebraic}} +\title{Real signature and Clifford signs \citet{Chapter II, Section 2.9, pp. 65--66}{chevalley1954algebraic}} \lean/tauceti{TauCeti.realCliffordForm,TauCeti.realCliffordForm_apply} \p{For #{p,q\ge0}, put diff --git a/trees/fcap-0014.tree b/trees/fcap-0014.tree index 216be5ae..ce3775c1 100644 --- a/trees/fcap-0014.tree +++ b/trees/fcap-0014.tree @@ -6,7 +6,7 @@ \tag{clifford} \taxon{Lemma} -\title{Finite hyperbolic reduction \citet{II.2.9, pp. 65--66}{chevalley1954algebraic}} +\title{Finite hyperbolic reduction \citet{Chapter II, Section 2.9, pp. 65--66}{chevalley1954algebraic}} \lean/tauceti{TauCeti.realCliffordBottIterEquiv,TauCeti.realCliffordSignatureReductionEquiv} \p{Chevalley splits a finite-dimensional real quadratic space into hyperbolic planes and a definite remainder. TauCeti combines that classical reduction with iteration of \ref{fcap-0013} and Kronecker equivalences to synthesize the explicit tensor and matrix packaging below. Iterating #{n} times gives diff --git a/trees/fcap-0019.tree b/trees/fcap-0019.tree index 36c1637b..1836f20a 100644 --- a/trees/fcap-0019.tree +++ b/trees/fcap-0019.tree @@ -7,16 +7,16 @@ \title{Spin-representation roadmap} -\p{This appendix follows the mathematical dependencies of the +\p{This appendix follows the mathematics in the \href{https://github.com/TauCetiProject/TauCetiRoadmap/tree/main/TauCetiRoadmap/RepresentationTheory/SpinRepresentations}{spin-representation roadmap} -of \href{https://github.com/TauCetiProject/TauCeti}{Tau Ceti}. The filtered -Clifford algebra first exposes its exterior shadow. Reflections then lead to -the global Pin and Spin extensions, while bivectors provide the algebraic -infinitesimal orthogonal action. The Lie functor records the separate -differential bridge from smooth group homomorphisms. A polarization joins the -algebraic group and Lie constructions in the exterior spinor model. The -real-signature recurrence and classification form a parallel algebraic branch -and do not depend on the spinor-module or double-cover join.} +of \href{https://github.com/TauCetiProject/TauCeti}{Tau Ceti}. The associated +graded algebra of the filtered Clifford algebra is an exterior algebra. +Reflections give the Pin and Spin extensions, while bivectors give the +infinitesimal orthogonal action. Differentiating smooth group homomorphisms +gives the Lie functor. A polarization equips the exterior algebra with its +Clifford and Spin actions. The real Clifford classification follows from the +hyperbolic and one-sided recurrences together with the real base cases. These +Clifford-algebra calculations supply all the inputs to its proof.} \transclude{fcap-000F} diff --git a/trees/fcap-001F.tree b/trees/fcap-001F.tree index 3c9797e0..3f4b1a61 100644 --- a/trees/fcap-001F.tree +++ b/trees/fcap-001F.tree @@ -23,4 +23,4 @@ a general field and that square roots for all field elements suffice to normalize lifts. TauCeti's generic theorem instead assumes a field, a nontrivial finite-dimensional module, invertible #{2}, a nondegenerate quadratic form, and an explicit surjectivity proof. Its separably closed -specialization obtains that proof from the formal Cartan--Dieudonne route.} +specialization obtains that proof from the formalized Cartan--Dieudonne theorem.} diff --git a/trees/fcap-001Q.tree b/trees/fcap-001Q.tree index 16979ba5..3bfdad7c 100644 --- a/trees/fcap-001Q.tree +++ b/trees/fcap-001Q.tree @@ -8,11 +8,10 @@ \title{Differentiating smooth group homomorphisms} \p{The quadratic Clifford construction in the preceding section is -algebraic. A different bridge starts from a smooth homomorphism of Lie groups -and differentiates it at the identity. This produces the functor from Lie -groups to Lie algebras and explains which part of the Spin-representation -roadmap is generic differential geometry, before any Lie-group structure on -the abstract Spin and special orthogonal groups has been supplied.} +algebraic. Separately, differentiating a smooth homomorphism of Lie groups at +the identity produces a homomorphism of their Lie algebras. This defines the +Lie functor before any Lie-group structure on the abstract Spin and special +orthogonal groups has been supplied.} \transclude{fcap-001R} \transclude{fcap-001S} diff --git a/trees/fcap-001W.tree b/trees/fcap-001W.tree index 002ecf91..6f941114 100644 --- a/trees/fcap-001W.tree +++ b/trees/fcap-001W.tree @@ -6,18 +6,16 @@ \tag{lie} \taxon{Remark} -\title{Why explicit smoothness changes the roadmap +\title{Smooth homomorphisms and automatic smoothness \citet{Sections 2.1--2.4 and 2.8, pp. 9--13, 19--20}{liu2016lie}; \citet{Section 3.1.2, pp. 106--107}{isaev2018theory}} \p{The constructions in \ref{fcap-001R}--\ref{fcap-001V} start with a smooth homomorphism. Their tangent map, bracket law, functor laws, and -exponential naturality therefore do not require a theorem that upgrades a -continuous homomorphism to a smooth one. The generic theorem does not invoke -the closed-subgroup theorem; that theorem belongs to the later specialization -to concrete matrix subgroups. This is the dependency split proposed in -\href{https://github.com/TauCetiProject/TauCetiRoadmap/pull/224}{TauCetiRoadmap -PR 224}.} +exponential naturality use the differential geometry of smooth maps. The +automatic-smoothness theorem is needed when the homomorphism is only known to +be continuous. The closed-subgroup theorem is needed when a closed matrix +subgroup must first be given a Lie-group structure.} \p{The exponential input is separate from the tangent and bracket input. Likewise, the Baker--Campbell--Hausdorff calculation can first be made in a diff --git a/trees/fcap-001Y.tree b/trees/fcap-001Y.tree index be70772f..2d56a4c9 100644 --- a/trees/fcap-001Y.tree +++ b/trees/fcap-001Y.tree @@ -6,22 +6,16 @@ \tag{clifford} \taxon{Remark} -\title{Why algebraic periodicity is a separate branch -\citet{II.2.1, II.2.5, and II.2.9, pp. 42--46, 65--66}{chevalley1954algebraic}; +\title{Algebraic periodicity and real Pin and Spin groups +\citet{II.2.1 and II.2.5, pp. 42--46; Chapter II, Section 2.9, pp. 65--66}{chevalley1954algebraic}; \citet{I.4, Theorems 4.1 and 4.3, pp. 25--29}{lawson2016spin}} \p{The recurrences in \ref{fcap-0013}, \ref{fcap-0014}, and \ref{fcap-001X} use Clifford universal properties, orthogonal sums, tensor -products, coordinate isometries, and the real base entries. They do not use -the Spin representation, the structure theorem obtained from a spinor -module, or the Pin and Spin double covers. This is the algebraic branch of -Layer 7.} +products, coordinate isometries, and the real base entries.} -\p{The real groups #{\Pin(p,q)} and #{\Spin(p,q)} form a different branch. -Their actions, kernels, and algebraic extensions specialize the group theory -developed in \ref{fcap-0007}, and therefore genuinely consume the Layer-2 -Pin/Spin work. The distinction between these branches is the dependency -correction proposed in -\href{https://github.com/TauCetiProject/TauCetiRoadmap/pull/225}{TauCetiRoadmap -PR 225}. It changes the order in which the mathematics can be built; it does -not turn the roadmap proposal itself into a formal theorem.} +\p{The construction of the real groups #{\Pin(p,q)} and #{\Spin(p,q)} instead +specializes the actions, kernels, and algebraic +extensions developed in \ref{fcap-0007}. Thus the real Clifford +classification can be proved from Clifford-algebra calculations before these +group extensions are available.}