Alexandra A. Soskova
(Sofia University)
Enumeration Degree Spectra

The enumeration degree spectrum DS(A) of a countable structure A is the set of all enumeration degrees of the presentations of A on the natural numbers. The co-spectrum of A is the set of all lower bounds of DS(A). The talk is a survey on the relationships between the degree spectrum and the co-spectrum of A.

We will discuss also a Jump inversion theorem for degree spectra and some applications of it.