**SMS scnews item created by John Enyang at Sun 11 Mar 2012 1140**

Type: Seminar

Modified: Sun 11 Mar 2012 1142

Distribution: World

Expiry: 17 Mar 2012

**Calendar1: 16 Mar 2012 1205-1255**

**CalLoc1: Carslaw 175**

Auth: enyang@penyang.pc (assumed)

### Algebra Seminar

# Global Lie-Tresse theorem

### Kruglikov

#### Friday March 16, 12:05--12:55pm, Carslaw 175

###### Speaker:

Boris Kruglikov (University of Tromsų, Norway)

###### Title:

Global Lie-Tresse theorem

###### Abstract:

Consider an algebraic pseudogroup transitively acting on a smooth manifold (more generally on a geometric structure, more generally on an algebraic differential equation). This action naturally extends to the space of infinite jets (partial case: actions by Lie groups). By differential invariant we will understand a rational function on this space, which is invariant with respect to the prolonged action. Alternatively this is a non-linear scalar differential operator (defined globally except for singularities). The main theorem states that the algebra of all scalar differential invariants is generated by a finite number of differential invariants and invariant derivatives. This is the base for solution of the equivalence problem. A number of examples and counter-examples from geometry, algebra and physics (with both finite- and infinite-dimensional groups) will be presented.

The talk is based on joint work with Valentin Lychagin.

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After the seminar we will take the speaker to lunch.

See the Algebra Seminar web page for information about other seminars in the series.

John Enyang John.Enyang@sydney.edu.au