Full adelic orthogonal, special orthogonal, and Spin groups #
For a rational quadratic space and compatible compact-open reference subgroups, the full adelic point group is the product of its real point group with its finite adelic point group. The real factor has no integrality condition. The product topology uses the canonical local group topologies and the restricted-product topology at the finite places.
The real factor is retained for the study of rational diagonal points in the full adeles.
This file constructs all three full adelic groups and the continuous maps Spin → SO → O.
Their projections to finite adeles commute with these maps. Membership in the image of SO → O
is characterized by properness at every place; for a nondegenerate form on a finite-dimensional
space, the kernel of Spin → SO is characterized by scalar ±1 at every place. On a nonzero
space the signs are independent; on the zero space the Spin group is trivial.
Local isometries Q ⊗ ℝ ≃ Q' ⊗ ℝ and Q ⊗ ℚ_p ≃ Q' ⊗ ℚ_p which carry the reference subgroups
onto one another at almost every prime give isomorphisms of topological groups between the full
adelic groups of Q and Q', compatible with the maps Spin → SO → O. The finite component of
each is TauCeti.restrictedProductCongrRight, so forgetting the real place recovers the finite
adelic transport.
The real coordinate of a full adelic point x is x.1, and its finite coordinates are x.2 p.
The product and restricted-product extensionality lemmas therefore apply directly. All carriers
and maps are defined without nondegeneracy or a positive-dimension hypothesis.
Main definitions #
OrthogonalCompactOpens.fullAdelicOrthogonalCongr,OrthogonalCompactOpens.fullAdelicSpecialOrthogonalCongr,OrthogonalCompactOpens.fullAdelicSpinCongr: transport of full adelic points along local isometries.
Main results #
fullAdelicSpecialOrthogonalCongr_comp_fullAdelicSpinToSpecialOrthogonalandfullAdelicSpecialOrthogonalToOrthogonal_comp_fullAdelicSpecialOrthogonalCongr, in the namespaceTauCeti.QuadraticMap.OrthogonalCompactOpens: the transports intertwine the mapsSpin → SO → O.fullAdelicOrthogonalToFinite_comp_fullAdelicOrthogonalCongrand its special orthogonal and Spin analogues: forgetting the real place turns each full adelic transport into the corresponding finite adelic transport.
References #
- O. T. O'Meara, Introduction to Quadratic Forms (1963), §101.
- A. Weil, Adeles and Algebraic Groups (1982), Chapter I.
The full adelic orthogonal group O(V)(𝔸), with its unrestricted real factor.
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The full adelic special orthogonal group SO(V)(𝔸), with its unrestricted real factor.
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The full adelic Spin group Spin(V)(𝔸), with its unrestricted real factor.
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Full adelic orthogonal points form a topological group in the product topology.
Full adelic special orthogonal points form a topological group in the product topology.
Forget the real component of a full adelic orthogonal point.
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Forget the real component of a full adelic special orthogonal point.
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Forget the real component of a full adelic Spin point.
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The finite projection retains the finite component of an orthogonal point.
The finite projection retains the finite component of a special orthogonal point.
The finite projection retains the finite component of a Spin point.
The projection from full to finite adelic orthogonal points is continuous.
The projection from full to finite adelic special orthogonal points is continuous.
The projection from full to finite adelic Spin points is continuous.
The full adelic Spin projection, applying the local projection at the real place and the everywhere-preserving finite adelic projection at the finite places.
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The full adelic inclusion of special orthogonal points into orthogonal points.
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The full adelic Spin projection acts on the real and finite components separately.
The full adelic special orthogonal inclusion acts on the real and finite components separately.
The full adelic Spin projection is continuous in the product topology.
The full adelic inclusion of special orthogonal points is continuous.
Forgetting the real component commutes with the adelic Spin projection.
Forgetting the real component commutes with the adelic special orthogonal inclusion.
The full adelic inclusion SO → O is injective.
A full adelic isometry comes from adelic SO exactly when it is proper at the real place
and at every finite place.
For a nondegenerate form, a full adelic Spin element lies in the kernel exactly when each
component is 1 or -1 in its local Clifford algebra.
Transport along local isometries #
The isomorphism of full adelic orthogonal groups induced by a real isometry and by local isometries at the primes which carry the orthogonal reference subgroups onto one another at almost every prime.
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Full adelic orthogonal transport applies the real isometry to the real component and the local isometries to the finite components.
Inverse full adelic orthogonal transport applies the inverse isometries componentwise.
The isomorphism of full adelic special orthogonal groups induced by a real isometry and by local isometries at the primes which carry the special orthogonal reference subgroups onto one another at almost every prime.
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Full adelic special orthogonal transport applies the real isometry to the real component and the local isometries to the finite components.
Inverse full adelic special orthogonal transport applies the inverse isometries componentwise.
The isomorphism of full adelic Spin groups induced by a real isometry and by local isometries at the primes which carry the Spin reference subgroups onto one another at almost every prime.
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Full adelic Spin transport applies the real isometry to the real component and the local isometries to the finite components.
Inverse full adelic Spin transport applies the inverse isometries componentwise.
Full adelic transport intertwines the full adelic Spin projections.
Full adelic transport intertwines the full adelic inclusions of SO into O.
Forgetting the real component turns full adelic orthogonal transport into finite adelic orthogonal transport.
Forgetting the real component turns full adelic special orthogonal transport into finite adelic special orthogonal transport.
Forgetting the real component turns full adelic Spin transport into finite adelic Spin transport.