Steffen Lempp
Department of Mathematics
University of Wisconsin, Madison
Madison, WI 53706
lempp@math.wisc.edu

Title: The structure of the Sigma_2 enumeration degrees

Abstract: I will report on progress on deciding the AE theory of the Sigma_2
enumeration degrees (under partial ordering), in particular, that all finite
lattices are embeddable into the Sigma_2 enumeration degrees preserving 0 and
1 (joint work with A. Sorbi), and on progress toward a decision procedure for
the extension of embeddings problem (joint work with T. A. Slaman and A.
Sorbi).