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XIV Encuentro de Invierno Geometría, Mecánica y Teoría de Control<br />

Zaragoza, 6-7 February, 2012<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong><br />

<strong>Geometric</strong> <strong>Mechanics</strong>, Classical field theories and Poisson structures<br />

Research group ULL<br />

http://www.alojamientoavanzado.com/digeme<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


General research proposal<br />

To study, from a geometric perspective, different methods to simplify how obta<strong>in</strong><br />

the trajectories of a mechanical system (subject or not to non-holonomic<br />

constra<strong>in</strong>ts)<br />

solutions of dynamic equations <strong>in</strong> first order classical field theories<br />

Several geometric methods<br />

Reduction Theory<br />

Hamilton-Jacobi Theory<br />

Invariant volumes<br />

<strong>Geometric</strong> <strong>in</strong>tegrators<br />

<strong>Geometric</strong> tools<br />

Poisson structures and generalizations<br />

Multisymplectic structures<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


Research l<strong>in</strong>es<br />

Reduction Theory<br />

Reduction of symplectic Lie algebroids<br />

Reduction of the Jacobi structure on the sphere of the dual bundle to a Lie algebroid endowed with<br />

a bundle metric<br />

Reduction and reconstruction of non-autonomous hamiltonian systems and symplectic pr<strong>in</strong>cipal<br />

R-bundles<br />

Introduction of the notion of a multi-Poisson structure as the Poisson version of a multisymplectic<br />

structure. Application to the reduction of first-order classical field theories<br />

Marsden-We<strong>in</strong>ste<strong>in</strong> multisymplectic reduction. Application to the reduction of first-order classical<br />

field theories<br />

Hamilton-Jacobi Theory<br />

Hamilton-Jacobi theory for hamiltonian systems with respect to l<strong>in</strong>ear Poisson structures<br />

Hamilton-Jacobi theory and complete <strong>in</strong>tegrability for (generalized) non-holonomic mechanical<br />

systems<br />

Hamilton-Jacobi theory for first-order classical field theories <strong>in</strong> the Lie algebroid sett<strong>in</strong>g<br />

Tulczyjew’s triple for first-order classical field theories <strong>in</strong> the Lie algebroid<br />

sett<strong>in</strong>g<br />

Study of <strong>in</strong>variant volume forms for non-holonomic mechanical systems<br />

Introduction of the <strong>in</strong>tr<strong>in</strong>sic notion of Poisson symmetric space<br />

Local description on discrete mechanics on Lie groupoids. The exact discrete<br />

lagrangian on a Lie groupoid<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


eduction theory<br />

Autonomous hamiltonian systems<br />

The configuration space:<br />

Q<br />

The phase space of momenta:<br />

T ∗ Q<br />

Hamiltonian function: H : T ∗ Q → R<br />

Structure: The canonical symplectic structure Ω Q ∈ Ω 2 (T ∗ Q)<br />

Hamiltonian vector field: H Ω Q<br />

H ∈ X(T ∗ Q), i Ω H Q<br />

Ω Q = dH<br />

H<br />

Solutions of Hamilton equations: <strong>in</strong>tegral curves of H Ω Q<br />

H<br />

In the presence of a group of symmetries<br />

⇓<br />

The system can be reduced to a system with less freedom degrees<br />

Reduction and reconstruction processes ⇒ the solutions of Hamilton equations<br />

dp<br />

dt = − ∂H<br />

∂q ,<br />

dq<br />

dt = ∂H<br />

∂p<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


ν ∈ g ∗ φ ν : G ν × J −1 (ν) → J −1 (ν), G ν = {g ∈ G/ Ad ∗ ν = ν}<br />

reduction theory<br />

Marsden-We<strong>in</strong>ste<strong>in</strong> reduction Theorem<br />

<strong>in</strong>gredients:<br />

(M, Ω) symplectic manifold<br />

φ : G × M → M a free and proper symplectic action of a Lie group G<br />

J : M → g ∗ an Ad ∗ -equivariant momentum map associated with φ<br />

ξ M = H Ω J ξ<br />

, J(φ g (x)) = Ad ∗ g −1 (J(x)), for any ξ ∈ g, x ∈ M<br />

⇓<br />

(J −1 (ν)/G ν, Ω ν) is a symplectic manifold<br />

π ∗ ν Ων = i ∗ ν Ω<br />

π ν : J −1 (ν) → J −1 (ν)/G ν,<br />

i ν : J −1 (ν) → M<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


eduction theory<br />

Marsden-We<strong>in</strong>ste<strong>in</strong> reduction Theorem by stages<br />

G = H 1 × H 2<br />

<strong>Some</strong> Applications<br />

Reduce by the subgroup H 1 at a time and then to reduce by H 2<br />

⇕<br />

Reduce by G<br />

underwater vehicle dynamics and stability (Leonard and Marsden [1997])<br />

Applications to compressible fluids (Holm and Kupershmidt [1983])<br />

H closed and normal subgroup of G<br />

Reduce by H and then by a group related with G/H<br />

⇕<br />

Reduce by G<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


two applications of symplectic reduction<br />

cotangent reduction<br />

Kirillov-Kostant-Souriau Theorem<br />

Research group ULL<br />

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cotangent reduction<br />

(M, Ω) = (T ∗ Q, Ω Q )<br />

φ : G × Q → Q a free and proper action<br />

T ∗ φ : G × T ∗ Q → T ∗ Q free and proper action<br />

J : T ∗ Q → g ∗ Ad ∗ -equivariant hamiltonian momentum map<br />

J(α q)(ξ) = α q(ξ Q (q))<br />

ν ∈ g ∗<br />

⇓<br />

(J −1 (ν)/G ν, (Ω Q ) ν) reduced symplectic manifold<br />

+<br />

α ν ∈ Ω 1 (Q)<br />

G ν-<strong>in</strong>variant 1-form with values <strong>in</strong> J −1 (ν)<br />

⇓<br />

ϕ αν : (J −1 (ν)/G ν, (Ω Q ) ν) → (T ∗ (Q/G ν), Ω Q/Gν − B αν ) embedd<strong>in</strong>g<br />

ϕ αν<br />

is a symplectomorphism ⇐⇒ g = g ν<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


Kirillov-Kostant-Souriau Theorem<br />

Kirillov-Kostant-Souriau Theorem<br />

The coadjo<strong>in</strong>t orbits <strong>in</strong> the dual space of the Lie algebra of a Lie group admit a<br />

symplectic structure<br />

<strong>in</strong>gredients<br />

G a Lie group with Lie algebra g<br />

The free and proper action l : G × G → G,<br />

The symplectic manifold (T ∗ G ∼ = G × g ∗ , Ω G )<br />

The symplectic action T ∗ l : G × G × g ∗ → G × g ∗<br />

l(g, h) = l g (h) = gh.<br />

The Ad ∗ -equivariant momentum map J T ∗G : G × g ∗ → g ∗<br />

(J T ∗G ) −1 (ν) = {(g, Ad ∗ g ν)|g ∈ G} ≃ G<br />

⇓ Marsden-We<strong>in</strong>ste<strong>in</strong> symplectic reduction theorem<br />

(J T ∗G ) −1 (ν)/G ν ∼ = G/Gν ≃ O ν<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


Poisson reduction<br />

<strong>in</strong>gredients<br />

Poisson manifold (M, {·, ·})<br />

φ : G × M → M a free and proper canonical Poisson action<br />

⇓<br />

M/G a Poisson manifold<br />

{f 1 , f 2 } r ◦ π = {f 1 ◦ π, f 2 ◦ π} ,<br />

where π : M → M/G is the canonical projection and f 1 , f 2 ∈ C ∞ (M/G)<br />

M = T ∗ Q<br />

T ∗ φ : G × T ∗ Q → T ∗ Q with φ : G × M → M free and proper action<br />

T ∗ Q/G → Q/G l<strong>in</strong>ear Poisson manifold<br />

Q = G and φ = l : G × G → G<br />

⇓<br />

the symplectic leaves of T ∗ G/G are the coadjo<strong>in</strong>t orbits<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


L<strong>in</strong>ear Poisson structures on a vector bundle<br />

To extend the reduction process for l<strong>in</strong>ear Poisson structures on vector bundles<br />

A → M vector bundle<br />

{Λ A ∗ ∈ V 2 (A ∗ ) l<strong>in</strong>ear Poisson structure on A ∗ } ↔ {([[·, ·]], ρ) Lie algebroid structure on A}<br />

[[·, ·]] : Γ(A) × Γ(A) → Γ(A) Lie bracket<br />

ρ : A → TM vector bundle morphism (anchor map)<br />

[[X , fY ]] = f [[X , Y ]] + ρ(X )(f )Y , ∀X , Y ∈ Γ(A), ∀f ∈ C ∞ (M)<br />

⇓<br />

(A, [[·, ·]], ρ) Lie algebroid<br />

Schouten bracket [·, ·] : Γ(∧ p A) × Γ(∧ p′ A) → Γ(∧ p+p′ −1 A)<br />

The differential of A d A : Γ(∧ k A ∗ ) → Γ(∧ k A ∗ )<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


Symplectic Lie algebroids<br />

(A → M, [[·, ·]], ρ) Lie algebroid of rank 2n + Ω ∈ Γ(∧ 2 A ∗ )<br />

d A Ω = 0, (Ω) n ≠ 0<br />

⇓<br />

M Poisson manifold<br />

example:<br />

(τ : A → M, [[·, ·]], ρ) Lie algebroid of rank n<br />

T A A ∗ → A ∗ vector bundle<br />

(T A A ∗ ) a ∗ = {(a, v) ∈ A τ ∗ (a ∗ ) × T a ∗ A ∗ /ρ(a) = T a ∗ τ ∗ (v)}<br />

T A A ∗ → A ∗ is a Lie algebroid of rank 2n ≡ the cover of fiberwise l<strong>in</strong>ear Poisson manifold<br />

λ A ∈ Γ((T A A ∗ ) ∗ ), Ω A = −d T A A ∗ λ A<br />

⇓<br />

T A A ∗ → A ∗ is a symplectic Lie algebroid<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


eduction of symplectic lie algebroids<br />

Reduction process for Lie algebroids<br />

Reduction process for symplectic Lie algebroids <strong>in</strong> the presence of a momentum<br />

map<br />

Application to the symplectic cover of a fiberwise l<strong>in</strong>ear Poisson manifold<br />

J.C. Marrero, E. Padrón, M. Rodríguez-Olmos: Reduction of a symplectic Lie algebroid with momentum map and<br />

its application to fiberwise l<strong>in</strong>ear poisson structures Prepr<strong>in</strong>t 2011.<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


eduction of lie algebroids<br />

<strong>in</strong>gredients<br />

(A → M, [[·, ]], ρ, Ω) symplectic Lie algebroid<br />

Φ : G × A → A action by complete lifts associated with φ : G × M → M<br />

ψ : g → Γ(A) Lie algebra anti-morphism such that Φ ∗ : G × A ∗ → A ∗ action by Poisson automorphisms<br />

ξ A ∗ = H Ω̂ψ(ξ)<br />

⇓<br />

Φ T : TG × A → A an aff<strong>in</strong>e action of TG ∼ = G × g over A<br />

Φ T ((g, ξ), a x ) = Φ g (a x + ψ(ξ)(x))<br />

⇓<br />

A/TG is a Lie algebroid over M/G and ˜π : A → A/TG is a Lie algebroid epimorphism<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


Reduction of symplectic Lie algebroids<br />

<strong>in</strong>gredients<br />

(A → M, [[·, ·]], ρ, Ω) symplectic Lie algebroid<br />

Φ : G × A → A action by complete lifts<br />

J : M → g ∗ momentum map<br />

Adg−1 ∗ (J(x)) = J(φg (x)), ∀x ∈ M, ∀g ∈ G<br />

Φ ∗ g (Ω) = Ω and i ψ(ξ) Ω = d A J ξ , for all g ∈ G and ξ ∈ g<br />

⇓<br />

J T : A → g ∗ × g ∗ ,<br />

J T (a) = ((TJ ◦ ρ)(a), J(τ(a)))<br />

TG × A → A aff<strong>in</strong>e action<br />

(A ν = (J T ) −1 (0, ν)/TG ν → J −1 (ν)/G ν, Ω ν) symplectic Lie algebroid<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


the particular case of T A A ∗<br />

<strong>in</strong>gredients<br />

(T A A ∗ → A ∗ , Ω A ) symplectic Lie algebroid<br />

Φ : G × A → A action by complete lifts with respect to ψ : g → Γ(A)<br />

⇓<br />

(Φ, T Φ ∗ ) : G × T A A ∗ → T A A ∗<br />

ψ T : g → Γ(T A A ∗ )<br />

J A ∗ : A ∗ → g ∗ hamiltonian momentum map<br />

J A ∗ (α x )(ξ) = α x (ψ(ξ)(x))<br />

((T A A ∗ ) ν, Ω ν) → (T A 0,ν<br />

A ∗ 0,ν , Ω A 0,ν<br />

− (pr 1 ) ∗ B ν) symplectic Lie algebroid embedd<strong>in</strong>g<br />

isomorphism if and only if g = g ν<br />

A 0,ν = A/TG ν → M/G ν<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


Reduction of symplectic Lie algebroids<br />

new objectives:<br />

To apply this reduction process to new examples<br />

Bundle version reduction of the symplectic cover of a fiberwise l<strong>in</strong>ear Poisson<br />

manifold<br />

Reduction by stages of symplectic Lie algebroids<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


L<strong>in</strong>ear Poisson manifolds on a vector bundle with a fiber metric<br />

The cotangent sphere bundle of a Riemannian manifold (Q, g) of dimension n<br />

S n−1 (T ∗ Q) = T ∗ 1 Q = {α ∈ T ∗ Q/g(α, α) = 1} → Q<br />

i S n−1 (T ∗ Q)<br />

: S n−1 (T ∗ Q) → T ∗ Q,<br />

λ ∈ Ω 1 (T ∗ Q) Liouville 1-form<br />

θ = −i ∗ S n−1 (T ∗ Q) (λ) ∈ Ω1 (S n−1 (T ∗ Q))<br />

θ ∧ (dθ) n is a volume form on T ∗ Q<br />

Unit sphere of a real Lie algebra with scalar product (g, [·, ·], < ·, · >) of dimension n<br />

S n−1 (g ∗ ) = {α ∈ g ∗ / < α, α >= 1}<br />

Λ g ∗ Lie-Poisson structure on g ∗<br />

¯Λ = Λ g ∗ − ∆ g ∗ ∧ i αg ∗ Λ g ∗ ∈ V2 (g ∗ ), Ē = i αg ∗ Λ g ∗ ∈ X(g∗ ),<br />

(g ∗ , (¯Λ, Ē)) Jacobi manifold<br />

[¯Λ, ¯Λ] = 2Ē ∧ ¯Λ, [Ē, ¯Λ] = 0<br />

⇓<br />

(S n−1 (g ∗ ), (¯Λ |S n−1 (g ∗ )<br />

, Ē |S n−1 (g ∗ )<br />

)) Jacobi manifold<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


(A ∗ , Λ A ∗ ) l<strong>in</strong>ear Poisson manifold with τ : A → M + g fiber bundle metric on A ∗<br />

⇓<br />

S n−1 (A ∗ ) → Q Jacobi manifold ?<br />

T A S n−1 (A ∗ )<br />

T A i<br />

✲<br />

T<br />

A A<br />

∗<br />

❄<br />

S n−1 (A ∗ )<br />

i<br />

✲<br />

❄<br />

T A S n−1 (A ∗ ) → S n−1 (A ∗ ) subalgebroid of T A A ∗ → A ∗<br />

A<br />

∗<br />

θ A = −(T A i) ∗ (λ A ) contact structure<br />

Ω A = −d T A A ∗ λ A symplectic structure<br />

θ A ∧ (d A θ A ) n ≠ 0<br />

⇓<br />

S n−1 (A ∗ ) Jacobi manifold<br />

A ∗ l<strong>in</strong>ear Poisson manifold<br />

i ∗ T A A ∗ = Ti(T A S 1 (A ∗ )) ⊕ i ∗ (< ∆ >), ∆ ∈ Γ(T A A ∗ )<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


The Jacobi structure on the sphere of a l<strong>in</strong>ear Poisson manifold on a vector<br />

bundle with fiber metric<br />

D. Ch<strong>in</strong>ea, J.C. Marrero, E. Padrón: The Jacobi structure on the sphere of a l<strong>in</strong>ear Poisson manifold on a vector<br />

bundle with fiber metric, work <strong>in</strong> progress<br />

New Objetives<br />

Give an explicit description of the Jacobi structure on S n−1 (A ∗ ) for known<br />

examples of Lie algebroids A<br />

Give a contact reduction procedure for contact Lie algebroids <strong>in</strong> the presence of<br />

momentum map, apply this result to the particular case of T S n−1 (A ∗ )<br />

Under certa<strong>in</strong> regularity conditions, study the manifold S n−1 (A ∗ )/E Is it aga<strong>in</strong> a<br />

Poisson manifold?<br />

R 2n symplectic manifold ⇒ S n−1 (R 2n ) contact manifold ⇒ S n−1 (R 2n )/E ∼ = CP<br />

n−1 symplectic manifold<br />

A ∗ l<strong>in</strong>ear Poisson manifold ⇒ S n−1 (A ∗ ) Jacobi manifold ⇒ S n−1 (A ∗ )/E Poisson manifold<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


Hamiltonian Systems<br />

Non-autonomous hamiltonian systems<br />

The configuration space:<br />

The phase space of momenta:<br />

extended version: T ∗ M<br />

π : M → R surjective submersion<br />

restricted version: V ∗ π V x π = T x π for all x ∈ M<br />

Structure: µ π : T ∗ M → V ∗ M<br />

µ π : T ∗ M → V ∗ π is a pr<strong>in</strong>cipal R-bundle<br />

ψ π : R × T ∗ M → T ∗ M,<br />

ψ π(s, α x ) = α x + sπ ∗ (dt)(x)<br />

ψ π is symplectic<br />

µ : (A, Ω) → V is a symplectic pr<strong>in</strong>cipal R-bundle if Ω is a symplectic structure on A<br />

such that the associated pr<strong>in</strong>cipal action ψ : R × A → A is symplectic<br />

µ : (A, Ω) → (V ∼ = A/R, Λ) Poisson morphism<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


canonical actions and momentum maps<br />

φ : G × A → A is a canonical action on the symplectic pr<strong>in</strong>cipal R-bundle<br />

µ : (A, Ω) → V<br />

φ is a symplectic action<br />

φ g ◦ ψ s = ψ s ◦ φ g<br />

for any g ∈ G, s ∈ R<br />

the 1-form ζ µ = i Zµ Ω is basic with respect to φ, i.e ζ µ(ξ A ) = 0 for any ξ ∈ g<br />

J : A → g ∗ Ad ∗ -equivariant momentum map for φ<br />

⇓<br />

+<br />

φ V : G × V → V Poisson action<br />

φ V (g, v) = µ(φ g (a))for any g ∈ G, v ∈ V<br />

J V : V → g ∗ Ad ∗ -equivariant momentum map for φ v<br />

J V (v) = J(a), with a ∈ µ −1 (v)<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


eduction process of symplectic R-pr<strong>in</strong>cipal bundle<br />

<strong>in</strong>gredients<br />

µ : (A, Ω) → V symplectic R-pr<strong>in</strong>cipal bundle<br />

φ : G × A → A canonical action with φ V : G × V → V is free and proper<br />

J : A → g ∗ Ad ∗ -equivariant momentum map<br />

ν ∈ g ∗ ⇓Marsden-We<strong>in</strong>ste<strong>in</strong> Th.<br />

⇓Poisson reduction Th.<br />

(A ν = J −1 (ν)/G ν, Ω ν) V ν = (J V ) −1 (ν)/G ν<br />

⇓<br />

µ ν : (A ν, Ω ν) → V ν is a symplectic pr<strong>in</strong>cipal R-bundle<br />

{·, ·} ν Poisson on V ν ≡ the Poisson bracket <strong>in</strong>duced by µ ν : A ν → V ν<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


standard symplectic pr<strong>in</strong>cipal R-bundle reduction theorem<br />

φ : G × M → M free and proper action<br />

π : M → R a G-<strong>in</strong>variant surjective submersion<br />

ν ∈ g ∗<br />

λ ν ∈ Ω 1 (M) a G ν-<strong>in</strong>variant 1-form with values <strong>in</strong> J −1<br />

ν (ν ′ )<br />

Then ˜π ν : M/G ν → R is a surjective submersion and there is a symplectic pr<strong>in</strong>cipal<br />

R-bundle embedd<strong>in</strong>g<br />

((T ∗ M) ν, (Ω M ) ν)<br />

ϕ λν<br />

(T ∗ (M/G ν), Ω M/Gν − B λν )<br />

(µ π) ν<br />

<br />

µ ˜πν<br />

<br />

(V ∗ π) ν<br />

ϕ V λν<br />

V ∗˜π ν<br />

B λν ∈ Ω 2 (T ∗ (M/G ν )) magnetic term associated with λ ν<br />

ϕ λν<br />

is a symplectic pr<strong>in</strong>cipal R-bundle isomorphism ⇔ g = g ν<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


Kirillov-Kostant-Souriau theorem (version for pr<strong>in</strong>cipal G-bundle<br />

with base space R<br />

<strong>in</strong>gredients<br />

φ : G × M → M free and proper action with pr<strong>in</strong>cipal G-bundle projection<br />

π : M → M/G ≃ R<br />

⇓<br />

T ∗ φ : G ×T ∗ M → T ∗ M + Ad ∗ -equivariant momentum map J : T ∗ M → g ∗<br />

⇓<br />

µ π : T ∗ M → V ∗ π be the standard symplectic R-bundle<br />

ν ∈ g ∗<br />

⇓ symplectic pr<strong>in</strong>cipal R-bundle reduction theorem<br />

(µ π) ν : ((T ∗ M) ν, (Ω M ) ν) → (V ∗ π) ν ∼ = M/Gν<br />

The Poisson structure on M/G ν<br />

The space of orbits M/G ν of the action of G ν on M admits a Poisson structure<br />

{·, ·} M/Gν and the symplectic leaf of M/G ν pass<strong>in</strong>g through the po<strong>in</strong>t [x] is<br />

symplectomorphic to O ν<br />

Research group ULL <strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


Non-autonomous hamiltonian systems<br />

I. Lacirasella, J. C. Marrero, E. Padrón: Reduction of symplectic R-bundles, Prepr<strong>in</strong>t 2012, arXiv:1201.4690<br />

To develop the bundle version of the reduction of the standard symplectic<br />

pr<strong>in</strong>cipal R-bundle<br />

To reconstruct the dynamics of a non-autonomous hamiltonian systems on a<br />

symplectic pr<strong>in</strong>cipal R-bundle from reduced dynamics.<br />

To study the reduction theory by stages of a symplectic pr<strong>in</strong>cipal R-bundle<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


multisymplectic geometry<br />

Classical field theories ⇔ multisymplectic formulation<br />

multisymplectic structure Ω ∈ Ω k (M), dΩ = 0<br />

i X Ω = 0 ⇒ X = 0,<br />

∀X ∈ X(M)<br />

example<br />

M = ∧ k T ∗ Q<br />

λ M (α)(X 1 , . . . , X k ) = α(T π(X 1 ), . . . , T π(X k )),<br />

π : ∧ k T ∗ Q → Q.<br />

Ω M = −dλ M es una forma multisimpléctica en Q<br />

Research group ULL<br />

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polisympletic structures<br />

k-polisymplectic structure on M<br />

⇕<br />

(ω 1 , . . . , ω k ) closed non-degenerate 2-forma R k -valued<br />

k∑<br />

¯ω = ω A ⊗ e A<br />

A=1<br />

{e 1 , . . . , e k } canonical base of R k .<br />

Example 1:<br />

(T 1 k )∗ Q := T ∗ Q⊕ (k . . . ⊕T ∗ Q,<br />

ω A = (π k,A<br />

Q )∗ ω,<br />

ω canonical symplectic form on T ∗ Q and π k,A<br />

Q : T ∗ Q⊕ . (k . . ⊕T ∗ Q → T ∗ Q the<br />

projection<br />

((T 1 k )∗ Q, ω 1 , . . . , ω k ) polisympletic manifold<br />

Research group ULL<br />

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polisympletic structures<br />

G a Lie group and g its Lie algebra<br />

g ∗ × (k . . . ×g ∗<br />

Coad k : G × g ∗ × (k . . . ×g ∗ → g ∗ × (k . . . ×g ∗<br />

(g, ν 1 , . . . , ν k ) ↦→ (Coad (g, ν 1 ), . . . , Coad (g, ν k ))<br />

(ν 1 , . . . , ν k ) ∈ g ∗ × (k . . . ×g ∗ coadjo<strong>in</strong>t k-orbits<br />

O (ν1 ,...,ν k ) = {Coad k (g, ν 1 , . . . , ν k ) | g ∈ G} ,<br />

is a polisymplectic manifold<br />

ω A ν : = (pr A ) ∗ ω νA ,<br />

pr A : : O (ν1 ,...,ν k ) → O νA , (ν 1 , . . . , ν k ), ↦→ ν A canonical projection and ω νA sympletic<br />

form of O νA<br />

Research group ULL <strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


We return to the symplectic and Poisson cases<br />

Ω symplectic structure<br />

⇕<br />

♭ ω : TM → T ∗ M, ♭ ω(v x ) = i vx ω x vector bundle isomorphism<br />

♭ ω([X , Y ]) = L X ♭ ω(Y ) − L Y ♭ ω(X ) − d(♭ ω(X )(Y )), ∀X , Y ∈ X(M)<br />

(M, Λ) Poisson manifold<br />

⇓<br />

♯ Λ : T ∗ M → TM, ♯ Λ (α x ) = i αx Λ<br />

D = Im♯ Λ <strong>in</strong>tegrable distribution whose leaves are symplectic manifolds<br />

(T ∗ M, [[·, ·]], ♯ Λ ) Lie algebroid<br />

[[α, β]] = L ♯Λ (α)β − L ♯Λ (β)α − d(β(♯ Λ (α)))<br />

{ ♯Λ : T<br />

Λ Poisson structure ⇔<br />

∗ → TM vector bundle homomorphism<br />

♯ Λ ([[α, β]]) = [♯ Λ (α), ♯ Λ (β)] ∀α, β ∈ Ω 1 (M)<br />

Research group ULL<br />

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polisympletic structures<br />

¯ω k-poly-symplectic structure on M<br />

⇕<br />

♭ ω : TM → ♭ ω (TM) ⊆ (Tk 1 )∗ M := T ∗ M⊕ . k . . ⊕T ∗ M ♭ ω (v x ) = (i vx (ωx 1 ), . . . , ivx (ωk x ))<br />

isomorphism vector bundle from TM to a sub-bundle of T ∗ M⊕ . k . . ⊕T ∗ M<br />

Skew-symmetry:<br />

♭ ω (v x )(v x ) = (0, . . . , 0)<br />

(v x ∈ T x M, x ∈ M).<br />

Non degenerate condition: ♭ ω vector bundle monomorphism<br />

Ker (♭ ω ) = {0}<br />

Integrability condition:<br />

♭ ω ([X , Y ]) = L X ♭ ω (Y ) − L Y ♭ ω (X ) − d(♭ ω (X )(Y )),<br />

X , Y ∈ X(M)<br />

Research group ULL<br />

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Poli-Poisson structures<br />

(S, ♯) poli-Poisson structure<br />

⇕<br />

S vector sub-bundle of (Tk 1)∗ M<br />

♯ : S → TM vector bundle morphism<br />

Skew-symmetry: α i (♯(α)) = 0, α = (α 1 , . . . , α k ), i ∈ {1, . . . , k}<br />

Non degenerate condition: If α(♯(β)) = 0 ∀β ∈ S ⇒ ♯(α) = 0<br />

Integrability condition: α, β ∈ Γ(S)<br />

(<br />

)<br />

[♯(α), ♯(β)] = ♯ L ♯(α) β − L ♯(β) α − d(β(♯(α)))<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


polisympletic structures<br />

Polisymplectic manifold ⇒ Poli-Poisson manifold<br />

S = ♭ ω (TM) and ♯ = ♭ −1<br />

ω<br />

Poli-Poisson manifold of order k = 1 ≡ Poisson manifold<br />

properties:<br />

(M, S, ♯) poli-Poisson manifold⇒ D = Im♯ is <strong>in</strong>tegrable<br />

L a leaf of F D ⇒ polisymplectic structure<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


polisympletic reduction<br />

<strong>in</strong>gredients:<br />

(M, ¯ω = (ω 1 , . . . , ω k )) a poly-simplectic manifold<br />

Φ : G × M → M a proper and free action such that Φ ∗ g ω i = ω i ,<br />

∀g ∈ G<br />

π : M → M/G<br />

Im (♭ ¯ω ) ( ∩ [(V π) ◦ × . (k . . ×(V π) ◦ ] is a vector sub-bundle<br />

(♭ ¯ω ) −1 [((V π) ⊥ ) ◦ × . (k . . ×((V π) ⊥ ) ◦ ] ∩ [(V π) ◦ × . (k<br />

)<br />

. . × ∩ (V π) ◦ ] ∩ Im (♭ ¯ω )<br />

(V π) ⊥ =<br />

⇓<br />

k⋂<br />

(ω ♭ i )−1 ((V π) ◦ )<br />

i=1<br />

M/G is a poli-Poisson manifold<br />

D. Iglesias, J.C. Marrero, M. Vaquero: On poly-Poisson structures, work <strong>in</strong> progress<br />

⊂ V π<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


Kirillov-Kostant-Souriau Theorem (version for polisymplectic<br />

sett<strong>in</strong>g)<br />

G Lie group<br />

G acts on the poly-symplectic manifold (T 1 k )∗ G and satisfies the above conditions<br />

((T 1 k )∗ G)/G ∼ = g ∗ × k) . . . ×g ∗<br />

the leaves of the poly-symplectic foliation are the k-coadjo<strong>in</strong>t orbits<br />

J.C. Marrero, N. Román Roy, M. Salgado, S. Vilar<strong>in</strong>o: Reduction of polisymplectic structures, work <strong>in</strong> progress<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


multisymplectic sett<strong>in</strong>g<br />

New objetives<br />

To <strong>in</strong>troduce the notion of multi-Poisson structure. Application to the reduction<br />

of first order classical field theories.<br />

To develop the multisymplectic reduction. Application to the reduction of first<br />

order classical field theories<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>


Poisson reduction<br />

Thanks!!!!!<br />

Research group ULL<br />

<strong>Some</strong> <strong>problems</strong> <strong>in</strong> <strong>Geometric</strong> <strong>Mechanics</strong>

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