Dartmouth Logic Seminar

## Winter 2008

Seminar this term will meet Fridays at 2:00 pm in Kemeny 008.

DateSpeakerTitle
Jan 18
Jared Corduan
Dartmouth College
Recursion theoretic analysis of the Nash Williams Barrier Partition Theorem
Jan 25
Jared Corduan
Dartmouth College
$\omega^{\omega}$ is a partition ordinal
Feb 8
Jared Corduan
Dartmouth College
A partition result of Erdos and Milner
Feb 15
No seminar this week - Penelope Maddy will be giving a joint math/philosophy colloquium at 4.
Feb 22
Mia Minnes
Cornell University
Complexity of tree questions based on their presentations

How hard is it to tell if two trees are isomorphic? We use isomorphism invariants to place this question on the analytical hierarchy for different classes of trees (namely, recursive partial order trees, automatic partial order trees, and automatic successor trees). This is joint work with Bakhadyr Khoussainov.
Feb 29
Asher Kach
University of Connecticut
Computable embeddings of computable linear orders

In this talk, we'll discuss what the existence of a classical embedding between computable linear orders implies about the complexity (from a computability viewpoint) of such embeddings. Specifically, we'll demonstrate the existence of a non-scattered linear order having no computable presentation into which the rationals computably embed; and the existence of a non-well-ordered linear order having no computable presentation into which the negative integers computably embed. As time permits, we'll sharpen these results by increasing the minimal complexity of any embedding and by demonstrating the minimality (in terms of rank) of the examples presented. This work is joint with Joe Miller and Reed Solomon.
Mar 7
Brooke Andersen
Dartmouth College
Sets that fail to be $D$-complete
Mar 21
Francois Dorais
Cornell University
Class forcing in small universes