Calendar

Oct
26
Thu
Logic seminar: Borel determinacy IV (David Webb)
Oct 26 @ 2:55 pm – 3:55 pm
Nov
2
Thu
Logic Seminar: Borel Determinacy V
Nov 2 @ 2:55 pm – 3:55 pm
Nov
9
Thu
Logic seminar: Boreal Determinacy VI (Khan)
Nov 9 @ 2:55 pm – 3:55 pm
Nov
30
Thu
David Webb’s specialty exam: A new notion of effective dimension @ Keller Hall 402
Nov 30 @ 2:50 pm – 3:40 pm

David Webb will present a new notion of effective dimension, inescapable dimension, which is in a sense dual to complex packing dimension.

The latter was introduced by Freer and Kjos-Hanssen in 2013 in the context of trying to show that the reals of effective Hausdorff dimension 1 are not Medvedev above the bi-immune sets.

Webb will show that the two notions are incomparable, among other results.

Dec
7
Thu
Joint Analysis/Logic Seminar @ Keller 402
Dec 7 @ 2:55 pm – 3:45 pm

Speaker : Michael Yampolsky (University of Toronto)

Title : Computability of Julia sets.

Abstract : Informally speaking, a compact set in the plane is computable if there exists an algorithm to draw it on a computer screen with an arbitrary resolution. Julia sets are some of the best-known mathematical images, however, the questions of their computability and computational complexity are surprisingly subtle. I will survey joint results with M. Braverman and others on computability and complexity of Julia sets.

Feb
2
Fri
Logic seminar: David Ross
Feb 2 @ 2:30 pm – 3:20 pm

This semester the Logic Seminar continues at a new day and time, Fridays at 2:30 in Keller 314.

For the first meeting this Friday I will (probably) speak about _Skolem polynomials_:

Abstract:
Over 100 years ago Hardy proved that a certain large class of real functions
was linearly ordered by eventual domination. In 1956 Skolem asked
whether the subclass of integer exponential polynomials is *well*-ordered
by the Hardy ordering, and conjectured that its order type
is epsilon_0. (This class is the smallest containing 1, x, and closed
under +, x, and f^g.) In 1973 Ehrenfeucht proved that the class is
well-ordered, and since then there has been some progress on the order
type.

The proof of well-ordering is rather remarkable and very short, and I
will attempt to expose it (which is to say, cover it) in the hour.

David Ross

Feb
9
Fri
Logic seminar: Mushfeq Khan
Feb 9 @ 2:30 pm – 3:30 pm

Mushfeq Khan will speak on amenability and symbolic dynamics.
As usual the seminar is in Keller 314.

Feb
16
Fri
Logic seminar: David Webb
Feb 16 @ 2:30 pm – 3:30 pm

Continuing the theme of symbolic dynamics, I will demonstrate a proof of Simpson’s result that “Entropy = Dimension” for N^d and Z^d, and discuss some of Adam Day’s work generalizing these results to amenable groups.