B.A. Haverford College
Ph.D. University of Chicago
Areas of Expertise: Algebraic Geometry, especially Algebraic Cycles
The basic problem in Algebraic Geometry is to describe the solution sets of systems of polynomial equations. As a simple example consider the equation y2 + y - x3 + x = 0. The solution set (with point at infinity added) in real numbers x and y consists of two circles. If x and y are allowed to be complex numbers, the solutions form the surface of a donut. If x and y must be rational numbers, we obtain an infinite set with a natural group structure isomorphic to the integers. Finally, if x and y must be integers, we are asking when the product of two consecutive integers equals the product of three consecutive integers. This occurs only finitely many times. The notion of scheme encodes all this information into a single mathematical object and allows one to use knowledge about the solution set for one number system to deduce information about solution sets for other number systems.
One way to study schemes is by associating to them a number of algebraic ``models''. The idea is that the relatively simple models should detect fundamental properties of the complicated schemes. In fact some of these models such as the cohomology ring are now quite well understood and provide practical computational tools. Others, such as the Chow group, which is constructed using all the subvarieties of the given scheme and is aimed at detecting subtle properties that singular cohomology can not see, remain mysterious. I study the Chow group by trying to understand how it relates to the better understood algebraic invariants. The relationship with l-adic Galois modules and Hodge structures, is a focal point of my research (1,2,3,7,8,9,10). Questions about Chow groups lead to a broad range of geometric problems (4,5,6,11).
More detailed research description, complete publication list
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