Calendar

Apr
28
Fri
Logic Seminar: Jack Yoon @ Keller 404
Apr 28 @ 2:30 pm – 3:30 pm

Jack Yoon will continue his explication of Proof Mining.

May
5
Fri
Logic Seminar: David Webb
May 5 @ 1:00 pm – May 5 @ 2:00 pm

David Webb will speak at 1:00-2:00 in Keller 402

Title: Every Function Can be Computable

Abstract: I will relay an interesting result of Joel David Hamkins: that
there is an algorithm which can compute any function f of natural
numbers, if it is carried out in the right model of arithmetic
(corresponding to f). In particular, I will construct the necessary
models using Rosser sentences and describe the algorithm.

Aug
31
Thu
Logic seminar: David Ross
Aug 31 @ 2:50 pm – 3:40 pm

This semester the Logic Seminar will meet on Thursdays, 2:50 – 3:40 pm in Keller 402.

This Thursday we will have a (probably brief) organizational meeting.

Title: Some nonstandard remarks about Egyptian fractions

Abstract: An Egyptian fraction is a finite sum of fractions of the form $1/n$, where $n$ is a natural number. I’ll give simple proofs of some results about such fractions (also about Znám fractions). The proofs only require the compactness theorem from first order logic, though I’ll use the language of nonstandard analysis.

Sep
14
Thu
Logic Seminar: David Webb @ Keller 402
Sep 14 @ 2:50 pm – 3:40 pm

Title: A Simple Proof of a Theorem of Woodin

Abstract: In a similar spirit as my talk last semester about computing
and non-standard models, I will relay Joel David Hamkins’ new proof of a
theorem of Woodin: that there is a function that enumerates any finite
set (if computed in the correct model M of arithmetic), and which can
enumerate any extension of that set (if run in the correct end-extension
of M).

Sep
21
Thu
Logic seminar: Mushfeq Khan @ Keller 402
Sep 21 @ 2:55 pm – 3:55 pm

Title: Measure-Risking Arguments in Recursion Theory

Abstract: By way of introducing the idea of measure-risking, I will present a proof of Kurtz’s theorem that the Turing upward closure of the set of 1-generic reals is of full Lebesgue measure. Then I will show how a stronger form of the theorem (due originally to Kautz) can be obtained by framing the proof as a “fireworks argument”, following a recent paper of Bienvenu and Patey.

Sep
28
Thu
Logic Seminar: Mushfeq Khan @ Keller 402
Sep 28 @ 2:55 pm – 3:55 pm

Continuation of last week’s talk

Oct
5
Thu
Logic Seminar: Borel Determinacy I (Umar Gaffar) @ Keller 402
Oct 5 @ 2:55 pm – 3:55 pm

Title: Borel Determinacy I
Speaker: Umar Gaffar

We’re going through Ross Bryant’s presentation of Martin’s theorem (in ZFC) that Borel games are determined.

Oct
12
Thu
Logic Seminar: Borel Determinacy II (Khan) @ Keller 402
Oct 12 @ 2:55 pm – 3:55 pm