# Poisson Structure on manifolds with singularities

In my last post I wrote about an introduction to Poisson Structure, now I’m going to explain how we can describe a poisson structure
on a manifold with singularities, this work was made by **Maria Sorokina** in her paper: Poisson structure on manifolds with singularities, so if you want details you should read it, I’m sure you will get fun.

Firstly we recall the definition of poisson structure.

As Sorokina says in the paper, a singularity can cause heavy loads on systems parts, so the key here is consider an algebra whose spectrum coincides with la configuration space with singularities. In first place we need to use the Differential operator theory.

**Differential Operator**

Let be a -algebra, a linear differential operator of order is a -homomorphism with values in such that

where , the set of all differential operator is denoted by Diff. Now, we can define an quotient module by , which is called **the module of symbols of order **, in this way we can define the algebra of symbols for an algebra :

Since any manifold can be determined by the smooth -algebra on functions on it, for each on is the -algebra homomorphism . that assigns to every function its value at a point .

**Pullback of algebras**

Now, we’re going to describe the algebra desired as the pullback of two known algebras. Let , for manifolds . The pullback is unique up to a unique isomorphism, this means

where is a homomorphism for certain -algebra .

**Construction of differential operators**

Let be an algebra which is the cartesian product of the algebras and over the algebra . Let , then there exists a unique linear map , for such belongs to Diff.

In Sorokina’s paper, she considers as example, we’re going to consider and .

**Example**

Let us consider coordinate cross on the plane:

Algebra of smooth functions on the cross is given by the formula:

Applying the algorithm:

The differential operators:

For a non-zero order:

plus, and if

Poisson bracket:

where

So, we get the following conditions:

The algebra of symbols is Smbl

**Lemma**

**Proof:**
Let us define homomorphism from the algebra of symbols to

, we know that , let Smbl by Hadamard’s Lemma:

where

Since

Therefore, .

As we can see, work on spaces with singularities is nice, in my next post I’ll talk about how we can describe a poisson structure on manifolds with corners, the definition of manifolds with corners was given by Mr. Dominic Joyce in his paper: On manifolds with corners.