Colloquium: Pamela Harris (Williams)
Sep 7 @ 3:30 pm – 4:30 pm
Logic Seminar: Kameryn Williams
Sep 10 @ 2:30 pm – 3:20 pm

Title: A conceptual overview of forcing

Abstract: Paul Cohen—who visited UH Mānoa in the 1990s—introduced the method of forcing to prove that the failure of the continuum hypothesis is consistent with ZFC, the standard base axioms for set theory. Since then it has become a cardinal tool within set theory, being the main method for proving independence results and even enjoys use in proving ZFC results. In this talk I will give an introduction to forcing, focusing on the big picture ideas.

This talk is a sequel to my previous talk and a prequel to my next talk.

Logic Seminar: Kameryn Williams
Sep 17 @ 2:30 pm – 3:20 pm

Title: Forcing as a computational process

Abstract: In this talk we will consider computable structure theoretical aspects of forcing. Given an oracle for a countable model of set theory $M$, to what extent can we compute information about forcing extensions $M[G]$? The main theorem I will present gives a robustly affirmative answer in several senses.

* Given an oracle for the atomic diagram of a countable model of set theory $M$, then for any forcing notion $\mathbb P \in M$ we can compute an $M$-generic filter $G \subseteq \mathbb P$.

* From the $\Delta_0$ diagram for $M$ we can moreover compute the atomic diagram of the forcing extension $M[G]$, and indeed its $\Delta_0$ diagram.

* From the elementary for $M$ we can compute the elementary diagram of the forcing extension $M[G]$, and this goes level by level for the $\Sigma_n$ diagrams.

On the other hand, there is no functorial process for computing forcing extensions.

* If ZFC is consistent then there is no computable procedure (nor even a Borel procedure) which takes as input the elementary diagram for a countable model $M$ of ZFC and a partial order $\mathbb P \in M$ and returns a generic $G$ so that isomorphic copies of the same input model always result in the same corresponding isomorphic copy of $G$.

This talk is a sequel to my previous talk. The work in this talk is joint with Joel David Hamkins and Russell Miller.

Colloquium: Pamela Harris (Williams)
Oct 5 @ 3:30 pm – 4:30 pm
Logic seminar: Sam Birns
Oct 8 @ 2:30 pm – 3:30 pm
Colloquium- Yuriy Mileyko
Oct 12 @ 3:30 pm – 4:30 pm

Speaker: Yuriy Mileyko (UHM)
Title: Another look at recovering local homology from samples of stratified sets.

Recovering homological features of spaces from samples has become one of
the central themes in topological data analysis, which has led to many
successful applications. Most of the results in this area focus on
global homological features, whose recovery predicates on imposing well
understood geometric conditions on the underlying space. Existing work
on recovering local homological information of a space from samples has
been much less abundant, since the required local geometric conditions on
the underlying space may vary from point to point and are not easily
integrated into a global condition, unless the space is a smooth
manifold. In this talk, we show that such global conditions for
recovering local homological information can be obtained for a fairly
large class of stratified sets.

Logic seminar: David Ross
Oct 15 @ 2:30 pm – 3:30 pm

Prof. Ross will speak about Nathanson’s “Generalized Egyptian Fractions.” Usual time and place (2:30, K314).

In a paper earlier this year Mel Nathanson generalized the notion of
“Egyptian Fraction” and extended some results of Sierpinski to sets of
these generalized Egyptian fractions. I’ll give short nonstandard proofs of
further generalizations of these results.

Colloquium: Ricardo Teixeira (U. Houston-Victoria) @ Keller 301
Oct 19 @ 3:30 pm – 4:30 pm

Speaker: Ricardo Teixeira (U. Houston-Victoria)
Title: Teaching Precalculus in Hawaii

Abstract: Most students enjoy learning about applications of math concepts. In
this talk, we will show how Precalculus concepts can motivate students
in the University of Hawai`i at Mānoa. Some interesting and recreational
use of certain concepts will be explored. At the end, we will cover
other ideas such as how to develop and maintain an effective culture of
assessment that may be used for future improvement and more.