a moduli space of higgs bundles and a character variety ii...
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
A moduli space of Higgs bundles and a charactervariety II
Hitchin’s self-duality equations and non-abelian Hodge theory
Taejung Kim
Korea Institute for Advanced Study
January 12, 2010
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Main Goals
Non-abelian Hodge theory
Hitchin’s self-duality equations
Application: Goldman’s theorem, real variation of Hodgestructure, and Teichmuller components, etc.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Main Goals
Non-abelian Hodge theory
Hitchin’s self-duality equations
Application: Goldman’s theorem, real variation of Hodgestructure, and Teichmuller components, etc.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Main Goals
Non-abelian Hodge theory
Hitchin’s self-duality equations
Application: Goldman’s theorem, real variation of Hodgestructure, and Teichmuller components, etc.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Semi-stable Bundles
A holomorphic vector bundle E of rank l is said to besemi-stable if for all proper sub-bundles H of E we have
slope(H) =deg H
rank H≤ deg E
rank E= slope(E).
It is said to be a stable bundle if the strict inequality holds.
Any line bundle is stable.
A stable bundle is necessarily in-decomposable.
For any line bundle L, E is stable iff E⊗ L is stable.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Semi-stable Bundles
A holomorphic vector bundle E of rank l is said to besemi-stable if for all proper sub-bundles H of E we have
slope(H) =deg H
rank H≤ deg E
rank E= slope(E).
It is said to be a stable bundle if the strict inequality holds.
Any line bundle is stable.
A stable bundle is necessarily in-decomposable.
For any line bundle L, E is stable iff E⊗ L is stable.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Semi-stable Bundles
A holomorphic vector bundle E of rank l is said to besemi-stable if for all proper sub-bundles H of E we have
slope(H) =deg H
rank H≤ deg E
rank E= slope(E).
It is said to be a stable bundle if the strict inequality holds.
Any line bundle is stable.
A stable bundle is necessarily in-decomposable.
For any line bundle L, E is stable iff E⊗ L is stable.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Semi-stable Bundles
A holomorphic vector bundle E of rank l is said to besemi-stable if for all proper sub-bundles H of E we have
slope(H) =deg H
rank H≤ deg E
rank E= slope(E).
It is said to be a stable bundle if the strict inequality holds.
Any line bundle is stable.
A stable bundle is necessarily in-decomposable.
For any line bundle L, E is stable iff E⊗ L is stable.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Higgs bundle
Let E be a holomorphic vector bundle over a compactRiemann M. Then a Higgs field associated with E is aholomorphic section Φ of End(E)⊗ KM
A Higgs bundle is a pair (E,Φ) consisting of a holomorphicvector bundle and a Higgs field.
A stable Higgs bundle is a Higgs bundle such that for anyΦ-invariant proper sub-bundles H of E we haveslope(H) = deg H
rank H < deg Erank E = slope(E).
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Higgs bundle
Let E be a holomorphic vector bundle over a compactRiemann M. Then a Higgs field associated with E is aholomorphic section Φ of End(E)⊗ KM
A Higgs bundle is a pair (E,Φ) consisting of a holomorphicvector bundle and a Higgs field.
A stable Higgs bundle is a Higgs bundle such that for anyΦ-invariant proper sub-bundles H of E we haveslope(H) = deg H
rank H < deg Erank E = slope(E).
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Higgs bundle
Let E be a holomorphic vector bundle over a compactRiemann M. Then a Higgs field associated with E is aholomorphic section Φ of End(E)⊗ KM
A Higgs bundle is a pair (E,Φ) consisting of a holomorphicvector bundle and a Higgs field.
A stable Higgs bundle is a Higgs bundle such that for anyΦ-invariant proper sub-bundles H of E we haveslope(H) = deg H
rank H < deg Erank E = slope(E).
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Problem
How to prove
Irreducible RepresentationsOO
A.Weil
Stable Higgs Bundles oo ? // Irreducible Flat connections
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Self-duality equations
Let M be a compact Riemann surface of genus ≥ 2.d
′′AΦ = 0 Holomorphic condition
F (A) = [Φ,Φ∗] Unitary condition.
A ∈ A1(M; ad P) and Φ ∈ A1,0(M; ad P⊗C).
In the case of rank 1, d
′′AΦ = 0
F (A) = 0.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Self-duality equations
Let M be a compact Riemann surface of genus ≥ 2.d
′′AΦ = 0 Holomorphic condition
F (A) = [Φ,Φ∗] Unitary condition.
A ∈ A1(M; ad P) and Φ ∈ A1,0(M; ad P⊗C).
In the case of rank 1, d
′′AΦ = 0
F (A) = 0.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Solutions of self-dual equations and Higgs pairs
Theorem (N.Hitchin)
There is a one to one correspondence irreducible solutions of theSO(3) self-duality equations modulo unitary gauge transformationsand rank 2 stable Higgs pairs modulo complex gaugetransformations.
An SO(3)-bundle can be thought as an SU(2) or U(2)-bundle.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Solutions of self-dual equations and Higgs pairs
Theorem (N.Hitchin)
There is a one to one correspondence irreducible solutions of theSO(3) self-duality equations modulo unitary gauge transformationsand rank 2 stable Higgs pairs modulo complex gaugetransformations.
An SO(3)-bundle can be thought as an SU(2) or U(2)-bundle.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Idea of proof
Irreducible RepresentationsOO
A.Weil
33
sshhhhhhhhhhhhhhhhhhh
Stable Higgs BundlesStep 1
++WWWWWWWWWWWWWWWWWWW oo ? // Irreducible Flat connections
Step 3
Irreducible Solutions of the self-duality equations
Step 4
kkWWWWWWWWWWWWWWWWWWW
Step 2
OO
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Step 1 and Step 2
Hitchin (Cf. Donaldson (Narashimhan-Seshadri))
Given a stable pair (E,Φ), can we find (A,Φ) such thatF (A) + [Φ,Φ∗] = 0 and d
′′AΦ = 0?
Minimizing sequence w.r.t. an adapted metric on the orbit of(d ′′E ,Φ): ∫
M‖F (An) + [Φn,Φ
∗n]‖2 with d
′′An
Φn = 0.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Step 1 and Step 2
Hitchin (Cf. Donaldson (Narashimhan-Seshadri))
Given a stable pair (E,Φ), can we find (A,Φ) such thatF (A) + [Φ,Φ∗] = 0 and d
′′AΦ = 0?
Minimizing sequence w.r.t. an adapted metric on the orbit of(d ′′E ,Φ): ∫
M‖F (An) + [Φn,Φ
∗n]‖2 with d
′′An
Φn = 0.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Step 1 and Step 2
The Uhlenbeck’s weak compactness theorem: A limit (A,Φ)exits.
Stability implies that the limit (A,Φ) is actually in the orbit of(d ′′E ,Φ) by the complex gauge group.
Step 2: Once we find (A,Φ), the irreducible flat connection isgiven by
d ′A + d ′′A + Φ + Φ∗
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Step 1 and Step 2
The Uhlenbeck’s weak compactness theorem: A limit (A,Φ)exits.
Stability implies that the limit (A,Φ) is actually in the orbit of(d ′′E ,Φ) by the complex gauge group.
Step 2: Once we find (A,Φ), the irreducible flat connection isgiven by
d ′A + d ′′A + Φ + Φ∗
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Step 1 and Step 2
The Uhlenbeck’s weak compactness theorem: A limit (A,Φ)exits.
Stability implies that the limit (A,Φ) is actually in the orbit of(d ′′E ,Φ) by the complex gauge group.
Step 2: Once we find (A,Φ), the irreducible flat connection isgiven by
d ′A + d ′′A + Φ + Φ∗
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Step 3 and Step 4
Donaldson and Corlette
Definition
A ρ(π1(M))-equivariant function H : M → GL(n,C)/U(n) is calleda harmonic metric if it is an extremal of an energy functional
E(H) =
∫eM |dH|2
Problem: Given an irreducible flat PSL(2,C)-connection D onPC, is there a unique decomposition D = A + Φ + Φ∗ suchthat (A,Φ) satisfies the self-dual equations?
ad PC = ad P⊕iad P.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Step 3 and Step 4
Donaldson and Corlette
Definition
A ρ(π1(M))-equivariant function H : M → GL(n,C)/U(n) is calleda harmonic metric if it is an extremal of an energy functional
E(H) =
∫eM |dH|2
Problem: Given an irreducible flat PSL(2,C)-connection D onPC, is there a unique decomposition D = A + Φ + Φ∗ suchthat (A,Φ) satisfies the self-dual equations?
ad PC = ad P⊕iad P.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Step 3 and Step 4
Donaldson and Corlette
Definition
A ρ(π1(M))-equivariant function H : M → GL(n,C)/U(n) is calleda harmonic metric if it is an extremal of an energy functional
E(H) =
∫eM |dH|2
Problem: Given an irreducible flat PSL(2,C)-connection D onPC, is there a unique decomposition D = A + Φ + Φ∗ suchthat (A,Φ) satisfies the self-dual equations?
ad PC = ad P⊕iad P.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Step 3 and Step 4
Answer: Find a canonical metric to give a unitarydecomposition.
Theorem (Corlette,Donaldson)
Let (P,D) be a principal G -bundle with a flat connection. (P,D)admits a harmonic metric if and only if the Zariski closure of theholonomy group of D is a reductive subgroup of G .
Step 4: Once we find an irreducible (A,Φ), we may constructa stable Higgs bundle (E,Φ) by taking d ′′A.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Step 3 and Step 4
Answer: Find a canonical metric to give a unitarydecomposition.
Theorem (Corlette,Donaldson)
Let (P,D) be a principal G -bundle with a flat connection. (P,D)admits a harmonic metric if and only if the Zariski closure of theholonomy group of D is a reductive subgroup of G .
Step 4: Once we find an irreducible (A,Φ), we may constructa stable Higgs bundle (E,Φ) by taking d ′′A.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Step 3 and Step 4
Answer: Find a canonical metric to give a unitarydecomposition.
Theorem (Corlette,Donaldson)
Let (P,D) be a principal G -bundle with a flat connection. (P,D)admits a harmonic metric if and only if the Zariski closure of theholonomy group of D is a reductive subgroup of G .
Step 4: Once we find an irreducible (A,Φ), we may constructa stable Higgs bundle (E,Φ) by taking d ′′A.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Construction of the moduli space of the solutions of theself-duality equations
Space: A(M; P)×A1,0(M; ad P⊗C)
A(M; P) ks +3 A1(M; ad P) ks +3 A0,1(M; ad P⊗C)
In this identification, a Riemannian metric
g((Ψ1,Φ1), (Ψ2,Φ2)) = 2i
∫M
Tr(Ψ∗1 ∧Ψ2 + Φ2 ∧ Φ∗1)
I : (Ψ,Φ) 7→ (iΨ, iΦ)
J : (Ψ,Φ) 7→ (iΨ∗,−iΦ∗)
K : (Ψ,Φ) 7→ (−Ψ∗,Φ∗)
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Construction of the moduli space of the solutions of theself-duality equations
Space: A(M; P)×A1,0(M; ad P⊗C)
A(M; P) ks +3 A1(M; ad P) ks +3 A0,1(M; ad P⊗C)
In this identification, a Riemannian metric
g((Ψ1,Φ1), (Ψ2,Φ2)) = 2i
∫M
Tr(Ψ∗1 ∧Ψ2 + Φ2 ∧ Φ∗1)
I : (Ψ,Φ) 7→ (iΨ, iΦ)
J : (Ψ,Φ) 7→ (iΨ∗,−iΦ∗)
K : (Ψ,Φ) 7→ (−Ψ∗,Φ∗)
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Construction of the moduli space of the solutions of theself-duality equations
Space: A(M; P)×A1,0(M; ad P⊗C)
A(M; P) ks +3 A1(M; ad P) ks +3 A0,1(M; ad P⊗C)
In this identification, a Riemannian metric
g((Ψ1,Φ1), (Ψ2,Φ2)) = 2i
∫M
Tr(Ψ∗1 ∧Ψ2 + Φ2 ∧ Φ∗1)
I : (Ψ,Φ) 7→ (iΨ, iΦ)
J : (Ψ,Φ) 7→ (iΨ∗,−iΦ∗)
K : (Ψ,Φ) 7→ (−Ψ∗,Φ∗)
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Construction of the moduli space of the solutions of theself-duality equations
Space: A(M; P)×A1,0(M; ad P⊗C)
A(M; P) ks +3 A1(M; ad P) ks +3 A0,1(M; ad P⊗C)
In this identification, a Riemannian metric
g((Ψ1,Φ1), (Ψ2,Φ2)) = 2i
∫M
Tr(Ψ∗1 ∧Ψ2 + Φ2 ∧ Φ∗1)
I : (Ψ,Φ) 7→ (iΨ, iΦ)
J : (Ψ,Φ) 7→ (iΨ∗,−iΦ∗)
K : (Ψ,Φ) 7→ (−Ψ∗,Φ∗)
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Hyperkahler manifold
Hyperkahler structure:
ωI (X ,Y ) = g(IX ,Y )
ωJ(X ,Y ) = g(JX ,Y )
ωK (X ,Y ) = g(KX ,Y )
Holomorphic symplectic structure w.r.t. I :
ΩI ((Ψ1,Φ1), (Ψ2,Φ2)) = ωJ + iωK
=
∫M
Tr(Φ2 ∧Ψ1 − Φ1 ∧Ψ2).
Moment maps:
µωI
((A,Φ)) = F (A) + [Φ,Φ∗]
µΩI((A,Φ)) = d ′′AΦ
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Hyperkahler manifold
Hyperkahler structure:
ωI (X ,Y ) = g(IX ,Y )
ωJ(X ,Y ) = g(JX ,Y )
ωK (X ,Y ) = g(KX ,Y )
Holomorphic symplectic structure w.r.t. I :
ΩI ((Ψ1,Φ1), (Ψ2,Φ2)) = ωJ + iωK
=
∫M
Tr(Φ2 ∧Ψ1 − Φ1 ∧Ψ2).
Moment maps:
µωI
((A,Φ)) = F (A) + [Φ,Φ∗]
µΩI((A,Φ)) = d ′′AΦ
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Hyperkahler manifold
Hyperkahler structure:
ωI (X ,Y ) = g(IX ,Y )
ωJ(X ,Y ) = g(JX ,Y )
ωK (X ,Y ) = g(KX ,Y )
Holomorphic symplectic structure w.r.t. I :
ΩI ((Ψ1,Φ1), (Ψ2,Φ2)) = ωJ + iωK
=
∫M
Tr(Φ2 ∧Ψ1 − Φ1 ∧Ψ2).
Moment maps:
µωI
((A,Φ)) = F (A) + [Φ,Φ∗]
µΩI((A,Φ)) = d ′′AΦ
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Hyperkahler reduction
Hyperkahler reduction M =⋂3
i=1 µ−1i (0)/G
Theorem (Hitchin)
Let M be the moduli space of irreducible solutions to theself-duality equations on a rank 2 bundle of odd degree and fixeddeterminant over M with g(M) ≥ 2. Then
All the complex structures of the hyperkahler family otherthan ±I are equivalent
Moreover, they are a Stein manifold except (M, I ).
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Hyperkahler reduction
Hyperkahler reduction M =⋂3
i=1 µ−1i (0)/G
Theorem (Hitchin)
Let M be the moduli space of irreducible solutions to theself-duality equations on a rank 2 bundle of odd degree and fixeddeterminant over M with g(M) ≥ 2. Then
All the complex structures of the hyperkahler family otherthan ±I are equivalent
Moreover, they are a Stein manifold except (M, I ).
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Hyperkahler reduction
Hyperkahler reduction M =⋂3
i=1 µ−1i (0)/G
Theorem (Hitchin)
Let M be the moduli space of irreducible solutions to theself-duality equations on a rank 2 bundle of odd degree and fixeddeterminant over M with g(M) ≥ 2. Then
All the complex structures of the hyperkahler family otherthan ±I are equivalent
Moreover, they are a Stein manifold except (M, I ).
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Hitchin’s C∗-action
Hitchin’s circle action: (A,Φ) 7→ (A, e iθΦ).
Hitchin’s C∗-action: (A,Φ) 7→ (A, cΦ)
Using the Morse theory argument, we can calculate the Bettinumbers of M.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Hitchin’s C∗-action
Hitchin’s circle action: (A,Φ) 7→ (A, e iθΦ).
Hitchin’s C∗-action: (A,Φ) 7→ (A, cΦ)
Using the Morse theory argument, we can calculate the Bettinumbers of M.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Hitchin’s C∗-action
Hitchin’s circle action: (A,Φ) 7→ (A, e iθΦ).
Hitchin’s C∗-action: (A,Φ) 7→ (A, cΦ)
Using the Morse theory argument, we can calculate the Bettinumbers of M.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Dolbeault groupoid and Betti groupoid
Weil’s theorem and the SO(3) self-duality equations
(M, J) is a covering of
Hom(π1,PSL(2,C)
)odd ,irr/PSL(2,C).
Theorem
Hom(Γ,SL(2,C)
)odd ,irr/SL(2,C) is smooth, connected, and
simply-connected.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Dolbeault groupoid and Betti groupoid
Weil’s theorem and the SO(3) self-duality equations
(M, J) is a covering of
Hom(π1,PSL(2,C)
)odd ,irr/PSL(2,C).
Theorem
Hom(Γ,SL(2,C)
)odd ,irr/SL(2,C) is smooth, connected, and
simply-connected.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Generalizations
Theorem (Corlette,Donaldson,Hitchin,Simpson)
There is a one to one correspondence between stable Higgspairs over M and irreducible representationsρ : π1(M)→ GL(n,C).
There is a one to one correspondence between poly-stableHiggs pairs over M and reductive representationsρ : π1(M)→ GL(n,C).
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Generalizations
Theorem (Corlette,Donaldson,Hitchin,Simpson)
There is a one to one correspondence between stable Higgspairs over M and irreducible representationsρ : π1(M)→ GL(n,C).
There is a one to one correspondence between poly-stableHiggs pairs over M and reductive representationsρ : π1(M)→ GL(n,C).
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Real structure
Let (M, I ) be the moduli space of irreducible solutions to theself-duality equations on a rank 2 vector bundle of odd degree andfixed determinant. Define an involution
ιU : (A,Φ) 7→ (A,−Φ).
The fixed points of S1-action ⊆ The fixed points of ιU
µ(A,Φ) = 2i∫M Tr(Φ ∧ Φ∗) = ‖Φ‖2
L2 .
µ−1((d − 12 )π) =M2d−1 for g − 1 ≥ d > 0.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Real structure
Let (M, I ) be the moduli space of irreducible solutions to theself-duality equations on a rank 2 vector bundle of odd degree andfixed determinant. Define an involution
ιU : (A,Φ) 7→ (A,−Φ).
The fixed points of S1-action ⊆ The fixed points of ιU
µ(A,Φ) = 2i∫M Tr(Φ ∧ Φ∗) = ‖Φ‖2
L2 .
µ−1((d − 12 )π) =M2d−1 for g − 1 ≥ d > 0.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Real structure
Let (M, I ) be the moduli space of irreducible solutions to theself-duality equations on a rank 2 vector bundle of odd degree andfixed determinant. Define an involution
ιU : (A,Φ) 7→ (A,−Φ).
The fixed points of S1-action ⊆ The fixed points of ιU
µ(A,Φ) = 2i∫M Tr(Φ ∧ Φ∗) = ‖Φ‖2
L2 .
µ−1((d − 12 )π) =M2d−1 for g − 1 ≥ d > 0.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Real structure
Theorem (Hitchin)
The fixed points of ιU consist of complex submanifoldsM0,M2d−1(1 ≤ d ≤ g − 1) each of dimension 3g − 3 where
M0 is isomorphic to the moduli space of stable rank 2bundles of fixed determinant and odd degree.
M2d−1 is a holomorphic vector bundle of rank g − 2 + 2dover a 22g -fold covering of S2g−2d−1M.
Critical manifold: Normal bundle structure.
ιU on Hom(π1,PSL(2,C)
)/PSL(2,C).
Mk/Z2g2 is a holomorphic vector bundle of rank g − 1 + k
over S2g−2−kM for 0 ≤ k ≤ 2g − 2.
Rank 1 case
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Real structure
Theorem (Hitchin)
The fixed points of ιU consist of complex submanifoldsM0,M2d−1(1 ≤ d ≤ g − 1) each of dimension 3g − 3 where
M0 is isomorphic to the moduli space of stable rank 2bundles of fixed determinant and odd degree.
M2d−1 is a holomorphic vector bundle of rank g − 2 + 2dover a 22g -fold covering of S2g−2d−1M.
Critical manifold: Normal bundle structure.
ιU on Hom(π1,PSL(2,C)
)/PSL(2,C).
Mk/Z2g2 is a holomorphic vector bundle of rank g − 1 + k
over S2g−2−kM for 0 ≤ k ≤ 2g − 2.
Rank 1 case
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Real structure
Theorem (Hitchin)
The fixed points of ιU consist of complex submanifoldsM0,M2d−1(1 ≤ d ≤ g − 1) each of dimension 3g − 3 where
M0 is isomorphic to the moduli space of stable rank 2bundles of fixed determinant and odd degree.
M2d−1 is a holomorphic vector bundle of rank g − 2 + 2dover a 22g -fold covering of S2g−2d−1M.
Critical manifold: Normal bundle structure.
ιU on Hom(π1,PSL(2,C)
)/PSL(2,C).
Mk/Z2g2 is a holomorphic vector bundle of rank g − 1 + k
over S2g−2−kM for 0 ≤ k ≤ 2g − 2.
Rank 1 case
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Real structure
Theorem (Hitchin)
The fixed points of ιU consist of complex submanifoldsM0,M2d−1(1 ≤ d ≤ g − 1) each of dimension 3g − 3 where
M0 is isomorphic to the moduli space of stable rank 2bundles of fixed determinant and odd degree.
M2d−1 is a holomorphic vector bundle of rank g − 2 + 2dover a 22g -fold covering of S2g−2d−1M.
Critical manifold: Normal bundle structure.
ιU on Hom(π1,PSL(2,C)
)/PSL(2,C).
Mk/Z2g2 is a holomorphic vector bundle of rank g − 1 + k
over S2g−2−kM for 0 ≤ k ≤ 2g − 2.
Rank 1 case
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Real structure
Theorem (Hitchin)
The fixed points of ιU consist of complex submanifoldsM0,M2d−1(1 ≤ d ≤ g − 1) each of dimension 3g − 3 where
M0 is isomorphic to the moduli space of stable rank 2bundles of fixed determinant and odd degree.
M2d−1 is a holomorphic vector bundle of rank g − 2 + 2dover a 22g -fold covering of S2g−2d−1M.
Critical manifold: Normal bundle structure.
ιU on Hom(π1,PSL(2,C)
)/PSL(2,C).
Mk/Z2g2 is a holomorphic vector bundle of rank g − 1 + k
over S2g−2−kM for 0 ≤ k ≤ 2g − 2.
Rank 1 case
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Character variety
Character variety
Theorem (Narashimhan-Seshadri)
There is a one to one correspondence between stable holomorphicvector bundles and irreducible unitary representations.
Theorem (Hitchin)
Let π1(M) be the fundamental group of a compact Riemannsurface of genus g ≥ 2, and let Hom(π1,PSL(2,R))k denote thespace of homomorphisms of π1 to PSL(2,R) whose associatedRP1-bundle has Euler class k. ThenHom(π1,PSL(2,R))k/PSL(2,R) is a smooth manifold ofdimension (6g − 6) which is diffeomorphic to a complex vectorbundle of rank g − 1 + k over S2g−2−kM.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Character variety
Character variety
Theorem (Narashimhan-Seshadri)
There is a one to one correspondence between stable holomorphicvector bundles and irreducible unitary representations.
Theorem (Hitchin)
Let π1(M) be the fundamental group of a compact Riemannsurface of genus g ≥ 2, and let Hom(π1,PSL(2,R))k denote thespace of homomorphisms of π1 to PSL(2,R) whose associatedRP1-bundle has Euler class k. ThenHom(π1,PSL(2,R))k/PSL(2,R) is a smooth manifold ofdimension (6g − 6) which is diffeomorphic to a complex vectorbundle of rank g − 1 + k over S2g−2−kM.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Character variety
Character variety
Corollary (Milnor,Wood)
The Euler class k of any flat PSL(2,R)-bundle satisfies|k| ≤ 2g − 2.
Corollary (Goldman)
If g = 2 and k = 1, then
Hom(π1,PSL(2,R))1/PSL(2,R) ∼= M × R4.
When k = 2g − 2, then the Teichmuller space
C3g−3.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Character variety
Character variety
Corollary (Milnor,Wood)
The Euler class k of any flat PSL(2,R)-bundle satisfies|k| ≤ 2g − 2.
Corollary (Goldman)
If g = 2 and k = 1, then
Hom(π1,PSL(2,R))1/PSL(2,R) ∼= M × R4.
When k = 2g − 2, then the Teichmuller space
C3g−3.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Character variety
Character variety
Corollary (Milnor,Wood)
The Euler class k of any flat PSL(2,R)-bundle satisfies|k| ≤ 2g − 2.
Corollary (Goldman)
If g = 2 and k = 1, then
Hom(π1,PSL(2,R))1/PSL(2,R) ∼= M × R4.
When k = 2g − 2, then the Teichmuller space
C3g−3.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Real variation of Hodge structure
Variation of Hodge structure
Definition
A real variation of Hodge structure of a weight k over a Riemannsurface M is a flat real vector bundle (E,D) together with asmooth direct sum decomposition
EC = E⊗C =⊕
p+q=k
Ep,q
satisfying
Fr =⊕
p≥r Ep,q is a holomorphic subbundle of EC relative tothe holomorphic structure D ′′
Ds ∈ F r−1 ⊗ Ω1M for s ∈ F r
Ep,q = Eq,p
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Real variation of Hodge structure
Variation of Hodge structure
Definition
A real variation of Hodge structure of a weight k over a Riemannsurface M is a flat real vector bundle (E,D) together with asmooth direct sum decomposition
EC = E⊗C =⊕
p+q=k
Ep,q
satisfying
Fr =⊕
p≥r Ep,q is a holomorphic subbundle of EC relative tothe holomorphic structure D ′′
Ds ∈ F r−1 ⊗ Ω1M for s ∈ F r
Ep,q = Eq,p
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Real variation of Hodge structure
Variation of Hodge structure
Definition
A real variation of Hodge structure of a weight k over a Riemannsurface M is a flat real vector bundle (E,D) together with asmooth direct sum decomposition
EC = E⊗C =⊕
p+q=k
Ep,q
satisfying
Fr =⊕
p≥r Ep,q is a holomorphic subbundle of EC relative tothe holomorphic structure D ′′
Ds ∈ F r−1 ⊗ Ω1M for s ∈ F r
Ep,q = Eq,p
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Real variation of Hodge structure
Variation of Hodge structure
Definition
A real variation of Hodge structure of a weight k over a Riemannsurface M is a flat real vector bundle (E,D) together with asmooth direct sum decomposition
EC = E⊗C =⊕
p+q=k
Ep,q
satisfying
Fr =⊕
p≥r Ep,q is a holomorphic subbundle of EC relative tothe holomorphic structure D ′′
Ds ∈ F r−1 ⊗ Ω1M for s ∈ F r
Ep,q = Eq,p
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Real variation of Hodge structure
Period map
By taking the Hodge structures of a smooth family Xm ofalgebraic varieties over M, we may define a map Π : M → D whereD is a period domain. But Π is not well-defined. Up tomonodromy ρ : π1(M)→ Γ ⊂ Aut(HZ), we may define a periodmapping
Π : M → D/Γ.
It is well-known that if there exists a smooth family Xm ofalgebraic varieties over M then Π is a variation of Hodge structure(E,D).
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Real variation of Hodge structure
Period map
By taking the Hodge structures of a smooth family Xm ofalgebraic varieties over M, we may define a map Π : M → D whereD is a period domain. But Π is not well-defined. Up tomonodromy ρ : π1(M)→ Γ ⊂ Aut(HZ), we may define a periodmapping
Π : M → D/Γ.
It is well-known that if there exists a smooth family Xm ofalgebraic varieties over M then Π is a variation of Hodge structure(E,D).
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Real variation of Hodge structure
Ubiquity of variations of Hodge structure
Theorem (Simpson)
Let G be a reductive group. The fixed points of S1-action onHom(π1,G ) are the monodromy representations arising fromvariations of Hodge structure over M.
The ubiquity of variation of Hodge structure by C. Simpson.
Corollary (Simpson)
Let ρ ∈ Hom(π1,G ). Then for z ∈ C∗, limz→0 zρ exists inHom(π1,G ), i.e., any homomorphism π1 → G can be deformed tothe monodromy representation of a variation of Hodge structure.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Real variation of Hodge structure
Ubiquity of variations of Hodge structure
Theorem (Simpson)
Let G be a reductive group. The fixed points of S1-action onHom(π1,G ) are the monodromy representations arising fromvariations of Hodge structure over M.
The ubiquity of variation of Hodge structure by C. Simpson.
Corollary (Simpson)
Let ρ ∈ Hom(π1,G ). Then for z ∈ C∗, limz→0 zρ exists inHom(π1,G ), i.e., any homomorphism π1 → G can be deformed tothe monodromy representation of a variation of Hodge structure.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Further application
Hitchin-Teichmuller components
The number of components ofHom(π1,PSL(2,R))/PSL(2,R) is 4g − 3.
One of them is homeomorphic to R6g−6, Teichmuller space.
Theorem (Hitchin)
Let M be a compact oriented surface of genus ≥ 2 and let G R bethe adjoint group of the split real form of a complex simple Liegroup G C. Let Hom+(π1,G
R) denote the space of representationswhich act completely reducibly on the Lie algebra of G R. ThenHom(π1,G
R)+/G R has a connected component homeomorphic toa Euclidean space of dimension (2g − 2) dim G R.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Further application
Hitchin-Teichmuller components
The number of components ofHom(π1,PSL(2,R))/PSL(2,R) is 4g − 3.
One of them is homeomorphic to R6g−6, Teichmuller space.
Theorem (Hitchin)
Let M be a compact oriented surface of genus ≥ 2 and let G R bethe adjoint group of the split real form of a complex simple Liegroup G C. Let Hom+(π1,G
R) denote the space of representationswhich act completely reducibly on the Lie algebra of G R. ThenHom(π1,G
R)+/G R has a connected component homeomorphic toa Euclidean space of dimension (2g − 2) dim G R.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Further application
Hitchin-Teichmuller components
The number of components ofHom(π1,PSL(2,R))/PSL(2,R) is 4g − 3.
One of them is homeomorphic to R6g−6, Teichmuller space.
Theorem (Hitchin)
Let M be a compact oriented surface of genus ≥ 2 and let G R bethe adjoint group of the split real form of a complex simple Liegroup G C. Let Hom+(π1,G
R) denote the space of representationswhich act completely reducibly on the Lie algebra of G R. ThenHom(π1,G
R)+/G R has a connected component homeomorphic toa Euclidean space of dimension (2g − 2) dim G R.
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Further application
Convex RP2-structure
Definition
The above component is called a Hitchin-Teichmuller component.
Theorem (Choi,Goldman)
The Hitchin-Teichmuller component ofHom(π1,PSL(3,R))+/PSL(3,R) is the deformation space ofmarked convex RP2-structures.
When n ≥ 4 for Hom(π1,PSL(n,R))+/PSL(n,R), widelyopen (?)
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Further application
Convex RP2-structure
Definition
The above component is called a Hitchin-Teichmuller component.
Theorem (Choi,Goldman)
The Hitchin-Teichmuller component ofHom(π1,PSL(3,R))+/PSL(3,R) is the deformation space ofmarked convex RP2-structures.
When n ≥ 4 for Hom(π1,PSL(n,R))+/PSL(n,R), widelyopen (?)
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Further application
Convex RP2-structure
Definition
The above component is called a Hitchin-Teichmuller component.
Theorem (Choi,Goldman)
The Hitchin-Teichmuller component ofHom(π1,PSL(3,R))+/PSL(3,R) is the deformation space ofmarked convex RP2-structures.
When n ≥ 4 for Hom(π1,PSL(n,R))+/PSL(n,R), widelyopen (?)
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Further application
Convex RP2-structure
Definition
The above component is called a Hitchin-Teichmuller component.
Theorem (Choi,Goldman)
The Hitchin-Teichmuller component ofHom(π1,PSL(3,R))+/PSL(3,R) is the deformation space ofmarked convex RP2-structures.
When n ≥ 4 for Hom(π1,PSL(n,R))+/PSL(n,R), widelyopen (?)
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Introduction Self-duality equations and Higgs pair Geometry of the moduli space Correspondence Applications Appendix
Rank 1 case
Rank 1 case
The fixed point set of ιR is
J ///o/o/o Hom(π1,C∗) Hom(π1,R∗)? _ooKS
I ///o/o/o/o T∗ Jac(M) Jac2(M)× H1,0(M)? _oo
Hom(π1,R+) ∼= R2g is the identity component ofJac2(M)× H1,0(M).
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