Orthogonal, special orthogonal, and Spin points of the adeles away from a set of primes #
Let Q be a quadratic form on a finite-dimensional rational vector space V, let U be a
compatible family of compact-open reference subgroups of the local orthogonal and Spin groups
(TauCeti.QuadraticMap.OrthogonalCompactOpens), and let S be a set of primes. For a finite set
of places containing the archimedean one, S is the set of its finite places, and the adelic
points away from it are the restricted products over the primes outside S of the local
groups of Q โ โ_p, relative to U. This file forms them for each of O, SO and Spin, as
RestrictedProductGroupAway S of the reference families already used for the finite adelic
groups, so that the away groups are the factors split off by awayDecomposition. No finiteness
of S is needed for any of the constructions.
Every reference subgroup is open, so each away group is a Hausdorff topological group, locally
compact for O and Spin. The local projections Spin(V_p) โ SO(V_p) โ O(V_p) assemble into
continuous componentwise homomorphisms of away groups, and these commute with the restrictions
restrictAway S from the finite adelic groups, which forget the components at S. As for the
finite adelic groups, SO(V)(๐ธ^S) โ O(V)(๐ธ^S) is injective with image cut out by the
determinant at every prime outside S, and for a nondegenerate form on a nonzero space the
kernel of Spin(V)(๐ธ^S) โ SO(V)(๐ธ^S) consists of the elements whose every component is 1 or
-1.
Local isometries Q โ โ_p โ Q' โ โ_p at the primes outside S, carrying the reference subgroups
onto one another at almost every such prime, give isomorphisms of topological groups between the
groups away from S of Q and of Q', compatible with the maps Spin โ SO โ O. When the local
isometries are given at every prime, restricting away from S turns the finite adelic transport
TauCeti.restrictedProductCongrRight into the transport away from S.
When no finite prime is removed, the named empty-away equivalences identify all three point
groups with their finite adelic groups. They specialize the canonical topological reindexing
TauCeti.awayEmptyContinuousMulEquiv, preserve every prime coordinate, and have inverses given
by restrictAway โ
.
Main definitions #
TauCeti.QuadraticMap.OrthogonalCompactOpens.awayAdelicOrthogonal,TauCeti.QuadraticMap.OrthogonalCompactOpens.awayAdelicSpecialOrthogonal,TauCeti.QuadraticMap.OrthogonalCompactOpens.awayAdelicSpin: the point groups away fromS.TauCeti.QuadraticMap.OrthogonalCompactOpens.awayAdelicSpinToSpecialOrthogonalandTauCeti.QuadraticMap.OrthogonalCompactOpens.awayAdelicSpecialOrthogonalToOrthogonal: the componentwise projections.TauCeti.QuadraticMap.OrthogonalCompactOpens.awayAdelicOrthogonalCongr,TauCeti.QuadraticMap.OrthogonalCompactOpens.awayAdelicSpecialOrthogonalCongr,TauCeti.QuadraticMap.OrthogonalCompactOpens.awayAdelicSpinCongr: transport of points away fromSalong local isometries.OrthogonalCompactOpens.awayAdelicOrthogonalEmptyEquiv,OrthogonalCompactOpens.awayAdelicSpecialOrthogonalEmptyEquiv,OrthogonalCompactOpens.awayAdelicSpinEmptyEquiv: the canonical empty-away topological comparisons with finite adelic groups.
Main results #
OrthogonalCompactOpens.awayAdelicSpinToSpecialOrthogonal_comp_restrictAwayandOrthogonalCompactOpens.awayAdelicSpecialOrthogonalToOrthogonal_comp_restrictAway: the restrictions from the finite adelic groups commute with the componentwise projections.OrthogonalCompactOpens.mem_range_awayAdelicSpecialOrthogonalToOrthogonal_iff: the image ofSOinOaway fromSis cut out by the determinant at every prime outsideS.OrthogonalCompactOpens.mem_ker_awayAdelicSpinToSpecialOrthogonal_iff: the kernel ofSpin โ SOaway fromSis the componentwiseยฑ1.awayAdelicSpecialOrthogonalCongr_comp_awayAdelicSpinToSpecialOrthogonalandawayAdelicSpecialOrthogonalToOrthogonal_comp_awayAdelicSpecialOrthogonalCongr, in the namespaceOrthogonalCompactOpens: transport away fromScommutes withSpin โ SO โ O.OrthogonalCompactOpens.awayAdelicOrthogonalCongr_comp_restrictAwayand its special orthogonal and Spin versions: restriction away fromSintertwines finite adelic transport with transport away fromS.The
awayAdelic*EmptyEquiv_applyandawayAdelic*EmptyEquiv_symm_applylemmas give the coordinate and inverse formulas;OrthogonalCompactOpens.awayAdelicSpecialOrthogonalEmptyEquiv_spinToSpecialOrthogonalandOrthogonalCompactOpens.awayAdelicOrthogonalEmptyEquiv_specialOrthogonalToOrthogonalshow that the comparisons commute withSpin โ SO โ O.
References #
- O. T. O'Meara, Introduction to Quadratic Forms (1963), ยง101.
- A. Weil, Adeles and Algebraic Groups (1982), Chapter I.
The three point groups away from S #
The orthogonal group O(V)(๐ธ^S) of the adeles away from S: the restricted product over the
primes outside S of the local orthogonal groups relative to the reference subgroups
U.orthogonal p.
Instances For
The special orthogonal group SO(V)(๐ธ^S) of the adeles away from S: the restricted product
over the primes outside S of the local special orthogonal groups relative to the derived
reference subgroups U.specialOrthogonal p.
Instances For
The Spin group Spin(V)(๐ธ^S) of the adeles away from S: the restricted product over the
primes outside S of the local Spin groups relative to the reference subgroups U.spin p.
Instances For
The comparison when only the archimedean place is removed #
With no finite primes removed, the away adelic orthogonal group is canonically the finite adelic group. The comparison preserves every prime coordinate.
Instances For
With no finite primes removed, the away adelic special orthogonal group is canonically the finite adelic group. The comparison preserves every prime coordinate.
Instances For
With no finite primes removed, the away adelic spin group is canonically the finite adelic group. The comparison preserves every prime coordinate.
Instances For
The empty-away orthogonal comparison preserves each local coordinate.
The empty-away special orthogonal comparison preserves each local coordinate.
The empty-away spin comparison preserves each local coordinate.
The inverse empty-away orthogonal comparison is restriction away from the empty set.
The inverse empty-away special orthogonal comparison is restriction away from the empty set.
The inverse empty-away Spin comparison is restriction away from the empty set.
Topology #
The orthogonal reference subgroups at the primes outside S are open, which makes the
orthogonal group away from S a topological group.
The special orthogonal reference subgroups at the primes outside S are open, which makes the
special orthogonal group away from S a topological group.
The Spin reference subgroups at the primes outside S are open, which makes the Spin group
away from S a topological group.
The componentwise projections #
The componentwise projection Spin(V)(๐ธ^S) โ SO(V)(๐ธ^S), assembled from the local Spin
projections at the primes outside S.
Instances For
The Spin projection away from S is the local Spin projection at every prime outside S.
The Spin projection away from S is continuous.
The componentwise inclusion SO(V)(๐ธ^S) โ O(V)(๐ธ^S). It is well defined because the special
orthogonal reference subgroups are the preimages of the orthogonal ones.
Instances For
The inclusion of SO into O away from S is the local inclusion at every prime outside
S.
The inclusion of SO into O away from S is continuous.
The empty-away comparison commutes with the projection from Spin to SO.
The empty-away comparison commutes with the inclusion from SO to O.
Compatibility with the restrictions from the finite adeles #
Restricting a finite adelic Spin point away from S commutes with projecting it to SO.
Restricting a finite adelic special orthogonal point away from S commutes with including it
in O.
The image of SO and the kernel of the Spin projection #
The inclusion of SO into O away from S is injective.
An orthogonal point away from S comes from the special orthogonal group away from S
exactly when each of its components has determinant one. As for the finite adelic groups, the
derived reference subgroups make this exact: a proper local isometry in U.orthogonal p lies in
U.specialOrthogonal p.
For a nondegenerate form, a Spin point away from S projects to the
identity of SO(V)(๐ธ^S) exactly when each of its components is 1 or -1 in the local Clifford
algebra.
Transport along local isometries #
The isomorphism of orthogonal groups away from S induced by local isometries at the primes
outside S which carry the orthogonal reference subgroups onto one another at almost every such
prime.
Instances For
Orthogonal transport away from S applies the local isometry at every prime outside S.
Inverse orthogonal transport away from S applies the inverse local isometries.
The isomorphism of special orthogonal groups away from S induced by local isometries at
the primes outside S which carry the special orthogonal reference subgroups onto one another at
almost every such prime.
Instances For
Special orthogonal transport away from S applies the local isometry at every prime outside
S.
Inverse special orthogonal transport away from S applies the inverse local isometries.
The isomorphism of Spin groups away from S induced by local isometries at the primes
outside S which carry the Spin reference subgroups onto one another at almost every such
prime.
Instances For
Spin transport away from S applies the local isometry at every prime outside S.
Inverse Spin transport away from S applies the inverse local isometries.
Transport away from S intertwines the Spin projections away from S.
Transport away from S intertwines the inclusions of SO into O away from S.
Compatibility of transport with the restrictions from the finite adeles #
Restricting away from S turns finite adelic orthogonal transport into orthogonal transport
away from S.
Restricting away from S turns finite adelic special orthogonal transport into special
orthogonal transport away from S.
Restricting away from S turns finite adelic Spin transport into Spin transport away from
S.