One of the oldest disciplines in mathematics, geometry goes back to the work of Pythagoras and Euclid. Geometry in modern mathematics takes on a multitude of forms, many of which are studied here at UNSW.

The interests of the Geometry research group are very broad, including algebraic geometry, differential geometry, hyperbolic geometry, Banach space geometry and noncommutative geometry.

Algebraic geometry studies solutions to polynomial equations using techniques from algebra, geometry, topology and analysis. This rich subject is intimately connected to number theory. Differential geometry studies manifolds, a key concept used to formulate many of the ideas in physics, from relativity to string theory. Hyperbolic geometry was developed in the nineteenth century and is a geometry in which there are many lines parallel to a given line through a given point.

Noncommutative geometry is inspired by the tantalising prospect of extending the natural duality between commutative algebra and geometry to the noncommutative setting. It has revolutionised the theory of operator algebras and noncommutative noetherian rings.

### Group Members

- Daniel Chan
- Michael Cowling
- Ian Doust
- David Harvey
- Galina Levitina
- Alessandro Ottazzi
- Fedor Sukochev
- Mircea Voineagu
- Norman Wildberger
- Dmitriy Zanin

**Daniel Chan **works in noncommutative algebraic geometry, a branch of mathematics which explores various connections between non-commutative algebra and algebraic geometry. His main interest is in noncommutative surfaces, the simplest examples of which are sheaves of algebras on projective surfaces called orders. His work includes noncommutative versions of Mori's minimal model program and the study of moduli spaces for noncommutative algebras.

**Michael Cowling **is interested in sub-Finsler geometry, the differential geometry associated to systems of differential equations, and in the geometry of Lie groups, particularly in the question of when algebraic conditions ensure smoothness and so allow the application of differential geometric methods.

**Ian Doust**'s work in functional analysis has had an increasingly geometric aspect. In operator theory his research investigates the relationship between the geometry of compact sets in the plane and the algebraic properties of certain algebras of functions defined on such sets. In a quite different direction he has recently been investigating geometric properties (such as generalised roundness) in the metric space setting.

**David Harvey **is a computational number theorist, whose interest in geometry arises because many problems in number theory can now be turned into algebraic geometric questions. For example, Fermat's Last Theorem which was proved via a very difficult study of elliptic curves, which are the curves that arise as the zero sets of polynomials of degree 3 in two variables.

**Galina Levitina** is interested in the area of noncommutative (matrix) analysis, particularly in the method of multiple operator integral.

**Alessandro Ottazzi** is interested in sub-Riemannian geometry, which is the metric geometry for non-holonomic mechanical systems, and in Lie groups and Lie algebras theory. Lie groups provide a case study for sub-Riemannian spaces, in which the metric is left-invariant. In particular, he is interested in the mappings between such spaces that preserve certain properties of the metric (e.g., isometries, conformal and quasiconformal maps).

**Fedor Sukochev **- Noncommutative geometry is partly motivated by the study of solutions of integral and differential equations. Fedor is interested in the functional-analytical aspects of such a study and its applications to noncommutative geometry.

**Mircea Voineagu** works in algebraic geometry, in particular in the theory of cohomological invariants associated to algebraic varieties. Cohomological invariants like motivic cohomology, Lawson homology or etale cohomology can be used in problems of classification of algebraic varieties. For example, Artin and Mumford give example of a unirational variety that is not rational by using etale cohomology.

**Norman Wildberger **is the discoverer of Rational Trigonometry, a new completely algebraic framework for trigonometry and Euclidean geometry. This is developed in his 2005 book Divine Proportions: Rational Trigonometry to Universal Geometry. He has been extending this approach to Hyperbolic Geometry, to a new threefold symmetry in planar geometry called Chromogeometry, to Spherical Geometry and recently to Triangle Geometry. He is particularly interested in Pascal's Hexagrammum Mysticum. His video series WildTrig and UnivHypGeom at his *YouTube* channel are bringing geometry to a wide audience.

**Dmitriy Zanin** studies functions and the functions of functions, with applications ranging from quantum physics to signal processing.