(wünsch's) nearly invariant calculus for parabolic geometries · bibliography parabolic...
TRANSCRIPT
![Page 1: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/1.jpg)
Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
(Wunsch’s) nearly invariant calculus for parabolicgeometries
Jan Slovak
Masaryk University, Brno, Czech Republicjoint work with Andreas Cap
(and others over years — M.G. Eastwood, V. Soucek, A.R. Gover)
August 2, 2006
![Page 2: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/2.jpg)
Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Structure
1 Bibliography
2 Parabolic Geometries and Weyl connectionsCartan connections as analogies to affine geometry onmanifoldsWeyl structures, connections and Rho–tensors
3 Nearly invariant calculusInvariant and fundamenta differentials
![Page 3: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/3.jpg)
Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Structure
1 Bibliography
2 Parabolic Geometries and Weyl connectionsCartan connections as analogies to affine geometry onmanifoldsWeyl structures, connections and Rho–tensors
3 Nearly invariant calculusInvariant and fundamenta differentials
![Page 4: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/4.jpg)
Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Important sources
P. Gauduchon, Structures de Weyl-Einstein, espaces detwisteurs et varietes de type S1 × S3, J. reine angew. Math.469 (1995), 1–50.
A. Cap, J. Slovak, V. Soucek, Invariant operators onmanifolds with almost Hermitian symmetric structures, I.Invariant differentiation, Acta Math. Univ. Commenianae 66(1997), 33–69; II. Normal Cartan connections, Acta Math.Univ. Commenianae 66 (1997), 203–220; III. StandardOperators, Diff. Geom. Appl. (2000),
M.G. Eastwood, J. Slovak, Semi-holonomic Verma modules,J. of Algebra 197 (1997), 424–448
V. Wunsch, On conformally invariant differential operators,Math. Nachr. 129 (1986), 269–281.
T. Branson, Second order conformal covariants, Proc. Amer.Math Soc. 126 (1998), 1031–1042.
and many more ....
![Page 5: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/5.jpg)
Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Important sources
P. Gauduchon, Structures de Weyl-Einstein, espaces detwisteurs et varietes de type S1 × S3, J. reine angew. Math.469 (1995), 1–50.
A. Cap, J. Slovak, V. Soucek, Invariant operators onmanifolds with almost Hermitian symmetric structures, I.Invariant differentiation, Acta Math. Univ. Commenianae 66(1997), 33–69; II. Normal Cartan connections, Acta Math.Univ. Commenianae 66 (1997), 203–220; III. StandardOperators, Diff. Geom. Appl. (2000),
M.G. Eastwood, J. Slovak, Semi-holonomic Verma modules,J. of Algebra 197 (1997), 424–448
V. Wunsch, On conformally invariant differential operators,Math. Nachr. 129 (1986), 269–281.
T. Branson, Second order conformal covariants, Proc. Amer.Math Soc. 126 (1998), 1031–1042.
and many more ....
![Page 6: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/6.jpg)
Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Important sources
P. Gauduchon, Structures de Weyl-Einstein, espaces detwisteurs et varietes de type S1 × S3, J. reine angew. Math.469 (1995), 1–50.
A. Cap, J. Slovak, V. Soucek, Invariant operators onmanifolds with almost Hermitian symmetric structures, I.Invariant differentiation, Acta Math. Univ. Commenianae 66(1997), 33–69; II. Normal Cartan connections, Acta Math.Univ. Commenianae 66 (1997), 203–220; III. StandardOperators, Diff. Geom. Appl. (2000),
M.G. Eastwood, J. Slovak, Semi-holonomic Verma modules,J. of Algebra 197 (1997), 424–448
V. Wunsch, On conformally invariant differential operators,Math. Nachr. 129 (1986), 269–281.
T. Branson, Second order conformal covariants, Proc. Amer.Math Soc. 126 (1998), 1031–1042.
and many more ....
![Page 7: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/7.jpg)
Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Important sources
P. Gauduchon, Structures de Weyl-Einstein, espaces detwisteurs et varietes de type S1 × S3, J. reine angew. Math.469 (1995), 1–50.
A. Cap, J. Slovak, V. Soucek, Invariant operators onmanifolds with almost Hermitian symmetric structures, I.Invariant differentiation, Acta Math. Univ. Commenianae 66(1997), 33–69; II. Normal Cartan connections, Acta Math.Univ. Commenianae 66 (1997), 203–220; III. StandardOperators, Diff. Geom. Appl. (2000),
M.G. Eastwood, J. Slovak, Semi-holonomic Verma modules,J. of Algebra 197 (1997), 424–448
V. Wunsch, On conformally invariant differential operators,Math. Nachr. 129 (1986), 269–281.
T. Branson, Second order conformal covariants, Proc. Amer.Math Soc. 126 (1998), 1031–1042.
and many more ....
![Page 8: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/8.jpg)
Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Important sources
P. Gauduchon, Structures de Weyl-Einstein, espaces detwisteurs et varietes de type S1 × S3, J. reine angew. Math.469 (1995), 1–50.
A. Cap, J. Slovak, V. Soucek, Invariant operators onmanifolds with almost Hermitian symmetric structures, I.Invariant differentiation, Acta Math. Univ. Commenianae 66(1997), 33–69; II. Normal Cartan connections, Acta Math.Univ. Commenianae 66 (1997), 203–220; III. StandardOperators, Diff. Geom. Appl. (2000),
M.G. Eastwood, J. Slovak, Semi-holonomic Verma modules,J. of Algebra 197 (1997), 424–448
V. Wunsch, On conformally invariant differential operators,Math. Nachr. 129 (1986), 269–281.
T. Branson, Second order conformal covariants, Proc. Amer.Math Soc. 126 (1998), 1031–1042.
and many more ....
![Page 9: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/9.jpg)
Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Important sources
P. Gauduchon, Structures de Weyl-Einstein, espaces detwisteurs et varietes de type S1 × S3, J. reine angew. Math.469 (1995), 1–50.
A. Cap, J. Slovak, V. Soucek, Invariant operators onmanifolds with almost Hermitian symmetric structures, I.Invariant differentiation, Acta Math. Univ. Commenianae 66(1997), 33–69; II. Normal Cartan connections, Acta Math.Univ. Commenianae 66 (1997), 203–220; III. StandardOperators, Diff. Geom. Appl. (2000),
M.G. Eastwood, J. Slovak, Semi-holonomic Verma modules,J. of Algebra 197 (1997), 424–448
V. Wunsch, On conformally invariant differential operators,Math. Nachr. 129 (1986), 269–281.
T. Branson, Second order conformal covariants, Proc. Amer.Math Soc. 126 (1998), 1031–1042.
and many more ....
![Page 10: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/10.jpg)
Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Important sources
P. Gauduchon, Structures de Weyl-Einstein, espaces detwisteurs et varietes de type S1 × S3, J. reine angew. Math.469 (1995), 1–50.
A. Cap, J. Slovak, V. Soucek, Invariant operators onmanifolds with almost Hermitian symmetric structures, I.Invariant differentiation, Acta Math. Univ. Commenianae 66(1997), 33–69; II. Normal Cartan connections, Acta Math.Univ. Commenianae 66 (1997), 203–220; III. StandardOperators, Diff. Geom. Appl. (2000),
M.G. Eastwood, J. Slovak, Semi-holonomic Verma modules,J. of Algebra 197 (1997), 424–448
V. Wunsch, On conformally invariant differential operators,Math. Nachr. 129 (1986), 269–281.
T. Branson, Second order conformal covariants, Proc. Amer.Math Soc. 126 (1998), 1031–1042.
and many more ....
![Page 11: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/11.jpg)
Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Structure
1 Bibliography
2 Parabolic Geometries and Weyl connectionsCartan connections as analogies to affine geometry onmanifoldsWeyl structures, connections and Rho–tensors
3 Nearly invariant calculusInvariant and fundamenta differentials
![Page 12: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/12.jpg)
Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Cartan connection
Definition
Cartan geometries of type G/P are deformations of thehomogeneous space G → G/P with the Maurer–Cartan formω ∈ Ω1(G ; g):absolute parallelism ω ∈ Ω1(G, g) on a principal fiber bundleG → M with structure group P, enjoying suitable invarianceproperties with respect to the principal action of P:
ω(ζX )(u) = X for all X ∈ p, u ∈ G (the connectionreproduces the fundamental vertical fields)
(rb)∗ω = Ad(g−1) ω (the connection form is equivariantwith respect to the principal action)
ω|TuG : TuG → g is a linear isomorphism for all u ∈ G (theabsolute parallelism condition).
![Page 13: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/13.jpg)
Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Cartan connection
Definition
Cartan geometries of type G/P are deformations of thehomogeneous space G → G/P with the Maurer–Cartan formω ∈ Ω1(G ; g):absolute parallelism ω ∈ Ω1(G, g) on a principal fiber bundleG → M with structure group P, enjoying suitable invarianceproperties with respect to the principal action of P:
ω(ζX )(u) = X for all X ∈ p, u ∈ G (the connectionreproduces the fundamental vertical fields)
(rb)∗ω = Ad(g−1) ω (the connection form is equivariantwith respect to the principal action)
ω|TuG : TuG → g is a linear isomorphism for all u ∈ G (theabsolute parallelism condition).
![Page 14: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/14.jpg)
Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Cartan connection
Definition
Cartan geometries of type G/P are deformations of thehomogeneous space G → G/P with the Maurer–Cartan formω ∈ Ω1(G ; g):absolute parallelism ω ∈ Ω1(G, g) on a principal fiber bundleG → M with structure group P, enjoying suitable invarianceproperties with respect to the principal action of P:
ω(ζX )(u) = X for all X ∈ p, u ∈ G (the connectionreproduces the fundamental vertical fields)
(rb)∗ω = Ad(g−1) ω (the connection form is equivariantwith respect to the principal action)
ω|TuG : TuG → g is a linear isomorphism for all u ∈ G (theabsolute parallelism condition).
![Page 15: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/15.jpg)
Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Cartan connection
Definition
Cartan geometries of type G/P are deformations of thehomogeneous space G → G/P with the Maurer–Cartan formω ∈ Ω1(G ; g):absolute parallelism ω ∈ Ω1(G, g) on a principal fiber bundleG → M with structure group P, enjoying suitable invarianceproperties with respect to the principal action of P:
ω(ζX )(u) = X for all X ∈ p, u ∈ G (the connectionreproduces the fundamental vertical fields)
(rb)∗ω = Ad(g−1) ω (the connection form is equivariantwith respect to the principal action)
ω|TuG : TuG → g is a linear isomorphism for all u ∈ G (theabsolute parallelism condition).
![Page 16: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/16.jpg)
Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Parabolic geometries
Definition
Parabolic geometries are Cartan connections with the choice ofparabolic P in semisimple real G .Morphisms of the parabolic geometries are principal fiber bundlemorphisms ϕ : G → G′ with ϕ∗(ω′) = ω.
Fixed grading g = g−k ⊕ . . . g−1 ⊕ g0 ⊕ g1 ⊕ · · · ⊕ gk on Liealgebra g, p = g0 ⊕ g1 ⊕ · · · ⊕ gk , g0 is the reductive part in p,
also write P+ = exp p+ and G− = exp g− for thecorresponding nilpotent subgroups.
Unique decomposition g = g0· expΥ1· . . . · expΥk , g ∈ P,g0 ∈ G0, and Υi ∈ gi .
Grading element is the unique E ∈ g0 with adE|gi= i· idgi for
all i = −k, . . . , k.
![Page 17: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/17.jpg)
Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Parabolic geometries
Definition
Parabolic geometries are Cartan connections with the choice ofparabolic P in semisimple real G .Morphisms of the parabolic geometries are principal fiber bundlemorphisms ϕ : G → G′ with ϕ∗(ω′) = ω.
Fixed grading g = g−k ⊕ . . . g−1 ⊕ g0 ⊕ g1 ⊕ · · · ⊕ gk on Liealgebra g, p = g0 ⊕ g1 ⊕ · · · ⊕ gk , g0 is the reductive part in p,
also write P+ = exp p+ and G− = exp g− for thecorresponding nilpotent subgroups.
Unique decomposition g = g0· expΥ1· . . . · expΥk , g ∈ P,g0 ∈ G0, and Υi ∈ gi .
Grading element is the unique E ∈ g0 with adE|gi= i· idgi for
all i = −k, . . . , k.
![Page 18: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/18.jpg)
Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Parabolic geometries
Definition
Parabolic geometries are Cartan connections with the choice ofparabolic P in semisimple real G .Morphisms of the parabolic geometries are principal fiber bundlemorphisms ϕ : G → G′ with ϕ∗(ω′) = ω.
Fixed grading g = g−k ⊕ . . . g−1 ⊕ g0 ⊕ g1 ⊕ · · · ⊕ gk on Liealgebra g, p = g0 ⊕ g1 ⊕ · · · ⊕ gk , g0 is the reductive part in p,
also write P+ = exp p+ and G− = exp g− for thecorresponding nilpotent subgroups.
Unique decomposition g = g0· expΥ1· . . . · expΥk , g ∈ P,g0 ∈ G0, and Υi ∈ gi .
Grading element is the unique E ∈ g0 with adE|gi= i· idgi for
all i = −k, . . . , k.
![Page 19: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/19.jpg)
Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Parabolic geometries
Definition
Parabolic geometries are Cartan connections with the choice ofparabolic P in semisimple real G .Morphisms of the parabolic geometries are principal fiber bundlemorphisms ϕ : G → G′ with ϕ∗(ω′) = ω.
Fixed grading g = g−k ⊕ . . . g−1 ⊕ g0 ⊕ g1 ⊕ · · · ⊕ gk on Liealgebra g, p = g0 ⊕ g1 ⊕ · · · ⊕ gk , g0 is the reductive part in p,
also write P+ = exp p+ and G− = exp g− for thecorresponding nilpotent subgroups.
Unique decomposition g = g0· expΥ1· . . . · expΥk , g ∈ P,g0 ∈ G0, and Υi ∈ gi .
Grading element is the unique E ∈ g0 with adE|gi= i· idgi for
all i = −k, . . . , k.
![Page 20: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/20.jpg)
Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Parabolic geometries
Definition
Parabolic geometries are Cartan connections with the choice ofparabolic P in semisimple real G .Morphisms of the parabolic geometries are principal fiber bundlemorphisms ϕ : G → G′ with ϕ∗(ω′) = ω.
Fixed grading g = g−k ⊕ . . . g−1 ⊕ g0 ⊕ g1 ⊕ · · · ⊕ gk on Liealgebra g, p = g0 ⊕ g1 ⊕ · · · ⊕ gk , g0 is the reductive part in p,
also write P+ = exp p+ and G− = exp g− for thecorresponding nilpotent subgroups.
Unique decomposition g = g0· expΥ1· . . . · expΥk , g ∈ P,g0 ∈ G0, and Υi ∈ gi .
Grading element is the unique E ∈ g0 with adE|gi= i· idgi for
all i = −k, . . . , k.
![Page 21: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/21.jpg)
Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Curvature
Definition
The structure equations K = dω + 12 [ω, ω] define the curvature K
of the Cartan connection ω.
ω defines constant vector fields ω−1(X ), X ∈ g.
Trg ·ω−1(X )(u) = ω−1(Adg−1 ·X )(u·g).
Curvature function
κ(u)(X ,Y ) = K (ω−1(X )(u), ω−1(Y )(u))
= [X ,Y ]− ω(u)([ω−1(X ), ω−1(Y )]).
Curvature is a horizontal 2–form.
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Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Curvature
Definition
The structure equations K = dω + 12 [ω, ω] define the curvature K
of the Cartan connection ω.
ω defines constant vector fields ω−1(X ), X ∈ g.
Trg ·ω−1(X )(u) = ω−1(Adg−1 ·X )(u·g).
Curvature function
κ(u)(X ,Y ) = K (ω−1(X )(u), ω−1(Y )(u))
= [X ,Y ]− ω(u)([ω−1(X ), ω−1(Y )]).
Curvature is a horizontal 2–form.
![Page 23: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/23.jpg)
Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Curvature
Definition
The structure equations K = dω + 12 [ω, ω] define the curvature K
of the Cartan connection ω.
ω defines constant vector fields ω−1(X ), X ∈ g.
Trg ·ω−1(X )(u) = ω−1(Adg−1 ·X )(u·g).
Curvature function
κ(u)(X ,Y ) = K (ω−1(X )(u), ω−1(Y )(u))
= [X ,Y ]− ω(u)([ω−1(X ), ω−1(Y )]).
Curvature is a horizontal 2–form.
![Page 24: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/24.jpg)
Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Curvature
Definition
The structure equations K = dω + 12 [ω, ω] define the curvature K
of the Cartan connection ω.
ω defines constant vector fields ω−1(X ), X ∈ g.
Trg ·ω−1(X )(u) = ω−1(Adg−1 ·X )(u·g).
Curvature function
κ(u)(X ,Y ) = K (ω−1(X )(u), ω−1(Y )(u))
= [X ,Y ]− ω(u)([ω−1(X ), ω−1(Y )]).
Curvature is a horizontal 2–form.
![Page 25: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/25.jpg)
Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Curvature
Definition
The structure equations K = dω + 12 [ω, ω] define the curvature K
of the Cartan connection ω.
ω defines constant vector fields ω−1(X ), X ∈ g.
Trg ·ω−1(X )(u) = ω−1(Adg−1 ·X )(u·g).
Curvature function
κ(u)(X ,Y ) = K (ω−1(X )(u), ω−1(Y )(u))
= [X ,Y ]− ω(u)([ω−1(X ), ω−1(Y )]).
Curvature is a horizontal 2–form.
![Page 26: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/26.jpg)
Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Weyl connections
Definition
Weyl structure on a parabolic geometry (G, ω) is a G0 equivariantsection σ : G0 = G/P+ → G.
θ = σ∗ω− = θ−k + · · ·+ θ−1 : TG0 → g−k ⊕ · · · ⊕ g−1
γ = σ∗ω0 : TG0 → g0
P = σ∗ω+ = P1 + · · ·+ Pk : TG0 → p+ = g1 ⊕ · · · ⊕ gk .
On the underlying manifold M we obtain:
θ is a soldering form for M
γ is a linear connection form on M, θ + γ is the affine Weylconnection
P is a one–form on M valued in T ∗M
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Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Weyl connections
Definition
Weyl structure on a parabolic geometry (G, ω) is a G0 equivariantsection σ : G0 = G/P+ → G.
θ = σ∗ω− = θ−k + · · ·+ θ−1 : TG0 → g−k ⊕ · · · ⊕ g−1
γ = σ∗ω0 : TG0 → g0
P = σ∗ω+ = P1 + · · ·+ Pk : TG0 → p+ = g1 ⊕ · · · ⊕ gk .
On the underlying manifold M we obtain:
θ is a soldering form for M
γ is a linear connection form on M, θ + γ is the affine Weylconnection
P is a one–form on M valued in T ∗M
![Page 28: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/28.jpg)
Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Weyl connections
Definition
Weyl structure on a parabolic geometry (G, ω) is a G0 equivariantsection σ : G0 = G/P+ → G.
θ = σ∗ω− = θ−k + · · ·+ θ−1 : TG0 → g−k ⊕ · · · ⊕ g−1
γ = σ∗ω0 : TG0 → g0
P = σ∗ω+ = P1 + · · ·+ Pk : TG0 → p+ = g1 ⊕ · · · ⊕ gk .
On the underlying manifold M we obtain:
θ is a soldering form for M
γ is a linear connection form on M, θ + γ is the affine Weylconnection
P is a one–form on M valued in T ∗M
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Weyl connections
Definition
Weyl structure on a parabolic geometry (G, ω) is a G0 equivariantsection σ : G0 = G/P+ → G.
θ = σ∗ω− = θ−k + · · ·+ θ−1 : TG0 → g−k ⊕ · · · ⊕ g−1
γ = σ∗ω0 : TG0 → g0
P = σ∗ω+ = P1 + · · ·+ Pk : TG0 → p+ = g1 ⊕ · · · ⊕ gk .
On the underlying manifold M we obtain:
θ is a soldering form for M
γ is a linear connection form on M, θ + γ is the affine Weylconnection
P is a one–form on M valued in T ∗M
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Weyl connections
Definition
Weyl structure on a parabolic geometry (G, ω) is a G0 equivariantsection σ : G0 = G/P+ → G.
θ = σ∗ω− = θ−k + · · ·+ θ−1 : TG0 → g−k ⊕ · · · ⊕ g−1
γ = σ∗ω0 : TG0 → g0
P = σ∗ω+ = P1 + · · ·+ Pk : TG0 → p+ = g1 ⊕ · · · ⊕ gk .
On the underlying manifold M we obtain:
θ is a soldering form for M
γ is a linear connection form on M, θ + γ is the affine Weylconnection
P is a one–form on M valued in T ∗M
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Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Weyl connections
Definition
Weyl structure on a parabolic geometry (G, ω) is a G0 equivariantsection σ : G0 = G/P+ → G.
θ = σ∗ω− = θ−k + · · ·+ θ−1 : TG0 → g−k ⊕ · · · ⊕ g−1
γ = σ∗ω0 : TG0 → g0
P = σ∗ω+ = P1 + · · ·+ Pk : TG0 → p+ = g1 ⊕ · · · ⊕ gk .
On the underlying manifold M we obtain:
θ is a soldering form for M
γ is a linear connection form on M, θ + γ is the affine Weylconnection
P is a one–form on M valued in T ∗M
![Page 32: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/32.jpg)
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Weyl connections
Definition
Weyl structure on a parabolic geometry (G, ω) is a G0 equivariantsection σ : G0 = G/P+ → G.
θ = σ∗ω− = θ−k + · · ·+ θ−1 : TG0 → g−k ⊕ · · · ⊕ g−1
γ = σ∗ω0 : TG0 → g0
P = σ∗ω+ = P1 + · · ·+ Pk : TG0 → p+ = g1 ⊕ · · · ⊕ gk .
On the underlying manifold M we obtain:
θ is a soldering form for M
γ is a linear connection form on M, θ + γ is the affine Weylconnection
P is a one–form on M valued in T ∗M
![Page 33: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/33.jpg)
Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus
Weyl connections
Definition
Weyl structure on a parabolic geometry (G, ω) is a G0 equivariantsection σ : G0 = G/P+ → G.
θ = σ∗ω− = θ−k + · · ·+ θ−1 : TG0 → g−k ⊕ · · · ⊕ g−1
γ = σ∗ω0 : TG0 → g0
P = σ∗ω+ = P1 + · · ·+ Pk : TG0 → p+ = g1 ⊕ · · · ⊕ gk .
On the underlying manifold M we obtain:
θ is a soldering form for M
γ is a linear connection form on M, θ + γ is the affine Weylconnection
P is a one–form on M valued in T ∗M
![Page 34: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/34.jpg)
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Natural bundles and tractor bundles
Natural bundles
P–representation λ on a vector space V provides the homogeneousvector bundle G ×P V and,more generally, the associated vector bundles
V = G ×P V
with standard fiber V over all manifolds with a parabolic geometryof the type G/P. These are the natural bundles V.
Tractor bundles
The natural bundles with G–modules V are called the tractorbundles
Note: The adjoint representation G provides the adjoint tractorbundles A, the standard representation of a matrix group on Rn
provides the standard tractors T .
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Natural bundles and tractor bundles
Natural bundles
P–representation λ on a vector space V provides the homogeneousvector bundle G ×P V and,more generally, the associated vector bundles
V = G ×P V
with standard fiber V over all manifolds with a parabolic geometryof the type G/P. These are the natural bundles V.
Tractor bundles
The natural bundles with G–modules V are called the tractorbundles
Note: The adjoint representation G provides the adjoint tractorbundles A, the standard representation of a matrix group on Rn
provides the standard tractors T .
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Natural bundles and tractor bundles
Natural bundles
P–representation λ on a vector space V provides the homogeneousvector bundle G ×P V and,more generally, the associated vector bundles
V = G ×P V
with standard fiber V over all manifolds with a parabolic geometryof the type G/P. These are the natural bundles V.
Tractor bundles
The natural bundles with G–modules V are called the tractorbundles
Note: The adjoint representation G provides the adjoint tractorbundles A, the standard representation of a matrix group on Rn
provides the standard tractors T .
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Transformations
Change of Weyl connections
If σ = σ· expΥ, and q = q1 + · · ·+ q` is a section of a naturalbundle, then:
q` =∑
‖i‖+j=`1i!(−1)iλ(Υ1)
i1 . . . λ(Υk)ik qj
∇ξs = ∇ξs+∑
‖i‖+j=01i!(−1)i
(ad(Υ1)
i1 . . .ad(Υk)ik (ξj))•s
Here i is a multiindex (i1, . . . , ik) with ij ≥ 0.We put i ! = i1! · · · ik ! and ‖i‖ = i1 + 2i2 + · · ·+ kik , while(−1)i = (−1)i1+···+ik
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Transformations
Change of Weyl connections
If σ = σ· expΥ, and q = q1 + · · ·+ q` is a section of a naturalbundle, then:
q` =∑
‖i‖+j=`1i!(−1)iλ(Υ1)
i1 . . . λ(Υk)ik qj
∇ξs = ∇ξs+∑
‖i‖+j=01i!(−1)i
(ad(Υ1)
i1 . . .ad(Υk)ik (ξj))•s
Here i is a multiindex (i1, . . . , ik) with ij ≥ 0.We put i ! = i1! · · · ik ! and ‖i‖ = i1 + 2i2 + · · ·+ kik , while(−1)i = (−1)i1+···+ik
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Transformations
Change of Weyl connections
If σ = σ· expΥ, and q = q1 + · · ·+ q` is a section of a naturalbundle, then:
q` =∑
‖i‖+j=`1i!(−1)iλ(Υ1)
i1 . . . λ(Υk)ik qj
∇ξs = ∇ξs+∑
‖i‖+j=01i!(−1)i
(ad(Υ1)
i1 . . .ad(Υk)ik (ξj))•s
Here i is a multiindex (i1, . . . , ik) with ij ≥ 0.We put i ! = i1! · · · ik ! and ‖i‖ = i1 + 2i2 + · · ·+ kik , while(−1)i = (−1)i1+···+ik
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Transformations
Change of Weyl connections
If σ = σ· expΥ, and q = q1 + · · ·+ q` is a section of a naturalbundle, then:
q` =∑
‖i‖+j=`1i!(−1)iλ(Υ1)
i1 . . . λ(Υk)ik qj
∇ξs = ∇ξs+∑
‖i‖+j=01i!(−1)i
(ad(Υ1)
i1 . . .ad(Υk)ik (ξj))•s
Here i is a multiindex (i1, . . . , ik) with ij ≥ 0.We put i ! = i1! · · · ik ! and ‖i‖ = i1 + 2i2 + · · ·+ kik , while(−1)i = (−1)i1+···+ik
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Tranformations – continued
Change of Rho–tensors
If σ = σ· expΥ, then:
Pi (ξ) =∑
‖j‖+`=i(−1)j
j! ad(Υk)jk · · · ad(Υ1)j1(ξ`) +∑k
m=1
∑‖j‖+m=i
j1=···=jm−1=0
(−1)j
j!(jm+1) ad(Υk)jk · · · ad(Υm)jm(∇ξΥm) +∑‖j‖+`=i
(−1)j
j! ad(Υk)jk · · · ad(Υ1)j1(P`(ξ)).
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Structure
1 Bibliography
2 Parabolic Geometries and Weyl connectionsCartan connections as analogies to affine geometry onmanifoldsWeyl structures, connections and Rho–tensors
3 Nearly invariant calculusInvariant and fundamenta differentials
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The derivatives
Invariant derivative
In analogy to the covariant derivatives we define ∇ω : C∞(G, V) →C∞(G, g∗− ⊗ V), ∇s(u)(X ) = ω−1(X )(u)·s ∈ V. This operationdoes not transform sections into sections, in general!
Fundamental derivative
The extension of the invariant derivative to argument X ∈ g
Dω : C∞(G, V) → C∞(G, g∗⊗V), ∇s(u)(X ) = ω−1(X )(u)·s ∈ Vis and invariant differential operator A∗ ⊗ V → V called thefundamental derivative.
Dωξ+ζs = ∇ξs + P(ξ) • s − ζ • s, ξ a vector in TM, ζ a vertical
vector on G0.
on all tractor bundles, the fundamental derivative is related tothe invariant linear connection ∇V
ξ s = ∇ξs + P(ξ) • s + ξ • s.
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The derivatives
Invariant derivative
In analogy to the covariant derivatives we define ∇ω : C∞(G, V) →C∞(G, g∗− ⊗ V), ∇s(u)(X ) = ω−1(X )(u)·s ∈ V. This operationdoes not transform sections into sections, in general!
Fundamental derivative
The extension of the invariant derivative to argument X ∈ g
Dω : C∞(G, V) → C∞(G, g∗⊗V), ∇s(u)(X ) = ω−1(X )(u)·s ∈ Vis and invariant differential operator A∗ ⊗ V → V called thefundamental derivative.
Dωξ+ζs = ∇ξs + P(ξ) • s − ζ • s, ξ a vector in TM, ζ a vertical
vector on G0.
on all tractor bundles, the fundamental derivative is related tothe invariant linear connection ∇V
ξ s = ∇ξs + P(ξ) • s + ξ • s.
![Page 45: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/45.jpg)
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The derivatives
Invariant derivative
In analogy to the covariant derivatives we define ∇ω : C∞(G, V) →C∞(G, g∗− ⊗ V), ∇s(u)(X ) = ω−1(X )(u)·s ∈ V. This operationdoes not transform sections into sections, in general!
Fundamental derivative
The extension of the invariant derivative to argument X ∈ g
Dω : C∞(G, V) → C∞(G, g∗⊗V), ∇s(u)(X ) = ω−1(X )(u)·s ∈ Vis and invariant differential operator A∗ ⊗ V → V called thefundamental derivative.
Dωξ+ζs = ∇ξs + P(ξ) • s − ζ • s, ξ a vector in TM, ζ a vertical
vector on G0.
on all tractor bundles, the fundamental derivative is related tothe invariant linear connection ∇V
ξ s = ∇ξs + P(ξ) • s + ξ • s.
![Page 46: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/46.jpg)
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The derivatives
Invariant derivative
In analogy to the covariant derivatives we define ∇ω : C∞(G, V) →C∞(G, g∗− ⊗ V), ∇s(u)(X ) = ω−1(X )(u)·s ∈ V. This operationdoes not transform sections into sections, in general!
Fundamental derivative
The extension of the invariant derivative to argument X ∈ g
Dω : C∞(G, V) → C∞(G, g∗⊗V), ∇s(u)(X ) = ω−1(X )(u)·s ∈ Vis and invariant differential operator A∗ ⊗ V → V called thefundamental derivative.
Dωξ+ζs = ∇ξs + P(ξ) • s − ζ • s, ξ a vector in TM, ζ a vertical
vector on G0.
on all tractor bundles, the fundamental derivative is related tothe invariant linear connection ∇V
ξ s = ∇ξs + P(ξ) • s + ξ • s.
![Page 47: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/47.jpg)
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Invariant jet operator
Both invariant and fundamental derivatives allow iteration!
1st order invariant jets
C∞(G, V) 3 s 7→ (s,∇ωs) ∈ C∞(G, V⊕ (g∗− ⊗ V))defines a natural operator (action given on J1V).
higher orders
C∞(G, V)P 3 s 7→ jkωs = (s,∇ωs, . . . , (∇ω)ks) ∈C∞(G, V⊕ · · · ⊕ (⊗kg∗− ⊗ V))P
is an invariant operator valued in semi–holonomic jets.
Note: Symmetrization provides similar formulae for holonomic jetsjkωs, but these are not equivariant!
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Invariant jet operator
Both invariant and fundamental derivatives allow iteration!
1st order invariant jets
C∞(G, V) 3 s 7→ (s,∇ωs) ∈ C∞(G, V⊕ (g∗− ⊗ V))defines a natural operator (action given on J1V).
higher orders
C∞(G, V)P 3 s 7→ jkωs = (s,∇ωs, . . . , (∇ω)ks) ∈C∞(G, V⊕ · · · ⊕ (⊗kg∗− ⊗ V))P
is an invariant operator valued in semi–holonomic jets.
Note: Symmetrization provides similar formulae for holonomic jetsjkωs, but these are not equivariant!
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Invariant jet operator
Both invariant and fundamental derivatives allow iteration!
1st order invariant jets
C∞(G, V) 3 s 7→ (s,∇ωs) ∈ C∞(G, V⊕ (g∗− ⊗ V))defines a natural operator (action given on J1V).
higher orders
C∞(G, V)P 3 s 7→ jkωs = (s,∇ωs, . . . , (∇ω)ks) ∈C∞(G, V⊕ · · · ⊕ (⊗kg∗− ⊗ V))P
is an invariant operator valued in semi–holonomic jets.
Note: Symmetrization provides similar formulae for holonomic jetsjkωs, but these are not equivariant!
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Invariant jet operator
Both invariant and fundamental derivatives allow iteration!
1st order invariant jets
C∞(G, V) 3 s 7→ (s,∇ωs) ∈ C∞(G, V⊕ (g∗− ⊗ V))defines a natural operator (action given on J1V).
higher orders
C∞(G, V)P 3 s 7→ jkωs = (s,∇ωs, . . . , (∇ω)ks) ∈C∞(G, V⊕ · · · ⊕ (⊗kg∗− ⊗ V))P
is an invariant operator valued in semi–holonomic jets.
Note: Symmetrization provides similar formulae for holonomic jetsjkωs, but these are not equivariant!
![Page 51: (Wünsch's) nearly invariant calculus for parabolic geometries · Bibliography Parabolic Geometries and Weyl connections Nearly invariant calculus Structure 1 Bibliography 2 Parabolic](https://reader034.vdocuments.net/reader034/viewer/2022042621/5f64493e8b5b4741a70d5f24/html5/thumbnails/51.jpg)
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Bianchi and Ricci identities
The Bianchi identity in terms of the invariant differnetial is0 =∑
cycl
([κ(X ,Y ),Z ]+κ([X ,Y ],Z )−κ(κ(X ,Y ),Z )−∇ω
Zκ(X ,Y )
)
while the Ricci identity reads∇ω
X∇ωY s −∇ω
Y∇ωX s = ∇ω
[X ,Y ] −∇ωκ−(X ,Y )s + κ≥0(X ,Y ) • s
Note: also available in terms of the fundamental derivative.
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Bianchi and Ricci identities
The Bianchi identity in terms of the invariant differnetial is0 =∑
cycl
([κ(X ,Y ),Z ]+κ([X ,Y ],Z )−κ(κ(X ,Y ),Z )−∇ω
Zκ(X ,Y )
)while the Ricci identity reads∇ω
X∇ωY s −∇ω
Y∇ωX s = ∇ω
[X ,Y ] −∇ωκ−(X ,Y )s + κ≥0(X ,Y ) • s
Note: also available in terms of the fundamental derivative.
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Bianchi and Ricci identities
The Bianchi identity in terms of the invariant differnetial is0 =∑
cycl
([κ(X ,Y ),Z ]+κ([X ,Y ],Z )−κ(κ(X ,Y ),Z )−∇ω
Zκ(X ,Y )
)while the Ricci identity reads∇ω
X∇ωY s −∇ω
Y∇ωX s = ∇ω
[X ,Y ] −∇ωκ−(X ,Y )s + κ≥0(X ,Y ) • s
Note: also available in terms of the fundamental derivative.
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The expansion
Proposition
Whatever expression we build of the invariant semiholonomic jetsof sections and the Cartan curvatures in terms of the invariantderivatives (or the fundamental derivatives) will expand inexpressions in the iterated covariant derivatives by means of theWeyl connections, the iterated covariant derivatives of thecurvature tensor of the Cartan connections and of the iteratedcovariant derivatives of the P tensors.
Example:∇ω
X∇ωY s(u) = (Dω)2s(u)(X ,Y ) = (∇X + P(v)(X ))(∇s(v))(Y ) =
(Tσ·γ−1(u)(X )− ω−1(P(v)(X ))(u))·(∇ω s)(u)(Y ) =∇X∇Y s(v) +∇[P(v)(X ),Y ]g−
s(v)− [P(v)(X ),Y ]p • s(v)
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Main theorem
Proposition
The transformation properties of any expansion of a formula ininvariant derivatives and Cartan curvatures are algebraic in Υ’s.
Theorem
Every expression in affine invariants of the Weyl connections withalgebraic transformation rules in Υ’s is an expansion of someexpression in invariant derivatives and the Cartan curvature.