NORTHEASTERNUNIVERSITY
MATHEMATICSDEPARTMENT


Geometry-Algebra-Singularities-Combinatorics 
Seminar

 
Some families of  Gorenstein algebras of height four,  and Hilbert schemes of curves on P³

 

Anthony Iarrobino

(Northeastern University)


Northeastern University

511 Lake Hall

1:30 p.m., Monday, January 14, 2002

 
 
 

  Abstract: Gorenstein Artinian (GA) algebras of given Hilbert function and socle degree j, quotients of a polynomial ring R in r-variables, may be parametrized as a locally closed subvariety of the projective space P(Rj) of degree-j forms in r up to k* multiple.  We ask:  Are the families PGor(H) of GA algebras of fixed Hilbert function H irreducible? What is the closure of PGor(H) in P(Rj)?

  We begin by answering these questions for complete interesections in two variables where there is a connection to determinantal ideals of Hankel matrices. This problem is also well understood in three variables, due to work of S.J. Diesel, J.-O. Kleppe, M. Boij, and others, based on the Buchsbaum-Eisenbud Pfaffian structure theorem for height three Gorenstein ideals. 

  I will give an overview of work joint with Hema Srinivasan, on certain families for r=4, where H=Hh=(1,4,7,h,7,4,1), 7< h< 11. When h=8,9 the components of PGor(H) are closely related to components of certain Hilbert schemes of curves in

  Which sequences H may occur is known for r=2,3, but not for r=4. We show
Theorem. Any Gorenstein sequence H=(1,4,7,... ) satisfies the condition, DH< j/2 is an O-sequence  so in particular is unimodal.  If also 8< h< 10, then PGOR(H) has several irreducible components.

The proofs use properties of minimal resolutions, the Hilbert schemes of curves in, the smoothness of
PGOR(H') for embedding dimension three (J. O. Kleppe), and the Gotzmann Hilbert scheme theorems. 


Home Web page: Alexandru I. Suciu Created: January 9, 2002
Maintained by:  Misha Kogan URL: http://www.math.neu.edu/~GASC/gas/anderson.html