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4 changes: 2 additions & 2 deletions trees/fcap-000T.tree
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\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.}
4 changes: 2 additions & 2 deletions trees/fcap-0010.tree
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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}}

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2 changes: 1 addition & 1 deletion trees/fcap-0011.tree
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\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
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2 changes: 1 addition & 1 deletion trees/fcap-0014.tree
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\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
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18 changes: 9 additions & 9 deletions trees/fcap-0019.tree
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\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}

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2 changes: 1 addition & 1 deletion trees/fcap-001F.tree
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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.}
9 changes: 4 additions & 5 deletions trees/fcap-001Q.tree
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\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}
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12 changes: 5 additions & 7 deletions trees/fcap-001W.tree
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\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
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22 changes: 8 additions & 14 deletions trees/fcap-001Y.tree
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\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.}
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