The Midwest Computability Seminar is a joint venture between the University of Chicago, the University of Notre Dame, and the University of Wisconsin-Madison. It meets once or twice per semester at the University of Chicago, and is attended by faculty and students from these universities and others in the area. The seminar started in the fall of 2008.

We are holding a special meeting to honor Carl Jockusch's exceptional and fundamental contributions to computability theory in general and the Midwest logic community in particular.

DATES: Saturday and Sunday, October 22-23, 2016.

PLACE: Ryerson Hall 352 (the Barn) and Eckhart Hall 206, The University of Chicago.

Organizers:

- Peter Cholak (University of Notre Dame)
- Denis Hirschfeldt (University of Chicago)
- Stuart Kurtz (University of Chicago)
- Tami Lakins (Allegheny College)
- Joe Mileti (Grinnell College)
- Joe Miller (University of Wisconsin-Madison)

Speakers:

- Eric Astor (University of Connecticut)
- Damir Dzhafarov (University of Connecticut)
- Denis Hirschfeldt (University of Chicago)
- Julia Knight (Universty of Notre Dame)
- Joe Mileti (Grinnell College)
- Ludovic Patey (University of California, Berkeley)
- Paul Schupp (University of Illinois at Urbana-Champaign)
- Ted Slaman (University of California, Berkeley)
- Bob Soare (University of Chicago)
- Linda Brown Westrick (University of Connecticut)

Schedule: All talks and coffee breaks will be in Ryerson 352 (the Barn), except as noted.

Saturday, October 22nd

- 9:00-9:50: Julia Knight
- 10:20-10:50: Joe Mileti
- 11:00-11:50: Paul Schupp

- 2:00-2:50: Ted Slaman (Eckhart 206)
- 3:00-3:50: Bob Soare (Eckhart 206)
- 4:20-5:10: Damir Dzhafarov
- 5:20-5:50: Ludovic Patey

- 6:30: Dinner at The Snail, 1649 East 55th Street.

Sunday, October 23rd

- 9:00-9:50: Denis Hirschfeldt
- 10:20-10:50: Eric Astor
- 11:00-11:30: Linda Brown Westrick

Titles and Abstracts:

Eric Astor

Title: Letting the Natural Numbers Vote (or, Upper Cones for Asymptotic Computation)

Abstract: It is well-known that upper cones for Turing computation have measure 0... or, in other words, that any set that is computable from "any meaningful fraction of sets

Damir Dzhafarov

Title: Ramsey's Theorem and Products in the Weihrauch Degrees

Abstract: One of Carl Jockusch's seminal contributions to computability theory was his 1972 paper on Ramsey's theorem, which spawned an industry of research into computable combinatorics, and gave rise to one of the most active and fruitful areas of study in reverse mathematics. Ramsey's theorem for pairs, RT(2), has proven to be a particularly rich source of questions in this area. A recent focus has been to try to understand RT(2) using the tools of computable reducibility and Weihrauch reducibility, which can be regarded as extending and refining the traditional framework of reverse mathematics. Much of this work has focused on teasing apart differences between variants of RT(2) that are either undetectable in the traditional framework of provability over RCA

Denis Hirschfeldt

Title: Notions of Computability-Theoretic Reducibility between Π

Abstract: I will discuss computable reducibility, Weihrauch reducibility, and some other notions of computability-theoretic reducibility between mathematical principles, including ones introduced in a recent joint paper with Carl, focusing in particular on Ramsey-theoretic principles.

Julia Knight

Title: Lengths of Roots of Polynomials in a Hahn Field (joint work with Karen Lange)

Abstract: For a divisible ordered Abelian group

Joe Mileti

Title: Reflections on Carl as a Researcher, Teacher, and Adviser

Ludovic Patey

Title: Coloring Trees in Reverse Mathematics

Abstract: The tree theorem asserts that given a finite coloring of pairs of comparable nodes in the full binary tree 2

Paul Schupp

Title: Reflections on Asymptotic Density and Computability

Abstract: Following the recent survey of the development of generic and coarse computability by Carl Jockusch and myself, I will try to outline the subject and make some comments on the general idea of the overall goal.

Ted Slaman

Title: Scott Sets and Turing Degrees

Abstract: In the 1970's Jockusch and Soare laid the foundation for the study of the Turing degrees of elements of Π

Robert Soare

Title: Fifty Years With Carl

Abstract: I first met Carl exactly fifty years ago at a meeting at Cornell in May, 1966 when we were both finishing our Ph.D. theses. We discovered we were working on similar topics. A year later we both moved to Illinois, Carl to UIUC and I to UIC. Our collaboration began then on a number of topics and continued over the next decades. I will describe some of the anecdotes and memories of my time with Carl with only a brief hint at the mathematics, but with the emphasis on the memories.

Linda Brown Westrick

Title: Dimension 1 Sequences Are Close to Randoms

Abstract: We give another answer to the informal question: are sequences of effective Hausdorff dimension 1 just random sequences that have been "messed up"? We show that a sequence has effective Hausdorff dimension 1 if and only if it differs from a Martin-Löf random sequence on a set of density zero. The proof makes essential use of Harper's Theorem concerning finite combinatorics of Hamming spheres. We also ask and answer similar questions for sequences of effective dimension

We have reserved blocks of rooms at two local hotels, LaQuinta Inn & Suites and the Chicago Lake Shore Hotel, for the nights of Oct. 21st and 22nd. These are adjacent to each other and under the same management, but have separate reservation numbers. In both cases, the rooms are under "Midwest Computability Seminar" and will be held until September 15th (so please book as soon as possible, since local hotel availability is quite limited). The rates we have been quoted and the phone numbers are as follows (when calling, ask for reservations):

LaQuinta Inn & Suites:

$149+tax / night

773-324-3000

Chicago Lake Shore Hotel:

$119+tax / night

773-288-5800

- Sept 23rd 2008. Antonio Montalbán - Logan Axon - Joe Miller
- Nov 11th 2008. Chris Conidis - Keng Meng (Selwyn) Ng - Peter Gerdes
- Feb 3rd 2009. David Diamondstone - Bart Kastermans - Richard A. Shore
- April 21st 2009. Dan Turetsky - Julia Knight - Ted Slaman
- Sept 29th 2009. Carl Jockusch - Rachel Epstein - Rebecca Weber
- Jan 26th 2010. Sara Quinn - John Wallbaum - Steffen Lempp - Reed Solomon
- May 11th 2010. Adam Day - Liang Yu - Rod Downey - Boris Zilber
- Sept 28th 2010. Maurice Chiodo - Peter Gerdes - Damir Dzhafarov - Andy Lewis
- Feb 15th 2011. Uri Andrews - Paola D'Aquino - David Diamondstone - Christopher Porter - Rebecca Steiner.
- Nov 1st 2011. Mingzhong Cai - Chris Conidis - Stephen Flood - Jeff Hirst - Asher Kach.
- Nov 15th 2012 Achilles Beros - Rod Downey - Jesse Johnson - Sam Sanders - Steven VanDendriessche - Matthew Wright.
- April 2nd 2013 Howard Becker - Denis Hirschfeldt - Paul Schupp.
- October 1st 2013 Peter Cholak - Mushfeq Khan - Victor Ocasio-González - Jonathan Stephenson
- April 29th, 2014 Rod Downey - Noam Greenberg - Gregory Igusa - Alexander Melnikov - Kyle Riggs
- September 30th, 2014 Eric Astor - Quinn Culver - Jack Lutz - Timothy McNicholl
- February 17th, 2015 Carl Jockusch - Julia Knight - Steffen Lempp
- January 28th, 2016 Reese Johnston - Rutger Kuyper - Mariya Soskova - Mars Yamaleev

If you haven't been receiving the announcements and would like to be included in the list, send an email to drh@math.uchicago.edu.