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Degree of Parabolic Quantum Groups - Dipartimento di Matematica ...

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1. POISSON ALGEBRAIC GROUPS<br />

In this chapter we recall some basic facts about Poisson groups that will<br />

prove useful in the study <strong>of</strong> quantum groups. The interested reader can find<br />

more details in a vast variety <strong>of</strong> articles and monographs, for example in<br />

[CP95], [KS98] or [CG97].<br />

1.1 Poisson manifolds<br />

1.1.1 Poisson algebras and Poisson manifolds<br />

Definition 1.1.1. A commutative associative algebra A over a field k is<br />

called a Poisson algebra if it is equipped with a k-bilinear operation { , } :<br />

A ⊗ A → A such that the following con<strong>di</strong>tions are satisfied:<br />

1. A is a Lie algebra with the bracket { , };<br />

2. the Leibniz rule are satisfied, i.e. for any a, b, c ∈ A, we have<br />

{ab, c} = a {b, c} + {a, c}b.<br />

If these con<strong>di</strong>tions are satisfied, the operation { , } is called Poisson bracket,<br />

and ξa = {a, ·} is called Hamiltonian derivation.<br />

Definition 1.1.2. Let A and B be a Poisson algebra over k. An algebra<br />

homomorphism f : A → B is called Poisson homomorphism if<br />

f ({a, b}) = {f(a), f(b)} .<br />

Poisson algebras form a category, with morphism being Poisson homomorphism.<br />

Definition 1.1.3. A smooth manifold M is called a smooth Poisson manifold<br />

if the algebra A = C ∞ (M) <strong>of</strong> smooth complex value function on M is<br />

equipped with a structure <strong>of</strong> Poisson algebra over C<br />

Definition 1.1.4. An affine algebraic k-variety M is called an affine algebraic<br />

Poisson k-variety if the algebra A = k[M] <strong>of</strong> regular function on M is<br />

equipped with a structure <strong>of</strong> Poisson algebra over k

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