Time: Friday, July 6 from 2:00 – 4:00 pm

Location: Keller 401

Draft of dissertation

Abstract: \

We provide some general tools that can be used for polynomials in any degree to show $G_\infty = \text{Aut}(T_\infty)$. We introduce the idea of Newton irreducibility to help push us closer to a proof to Odoni’s conjecture for monic integer polynomials when $d=4$. We also show that current techniques used in the literature will not work in proving Odoni’s conjecture for monic quartic polynomials. Finally, we look at how certain behaviors of the critical points of a polynomial $f(x) \in \mathbb{Q}[x]$ force it to not have full Galois image.

Draft of dissertation:

In this paper we study properties of groupoids by looking at their $C^∗$-algebras. We introduce a notion of rapid decay for transformation groupoids and we show that this is equivalent to the underlying group having the property of rapid decay. We show that our definition is equivalent to a number of other properties which are in direct correspondence to the group case. Additionally, given two bilipschitz equivalent discrete groups we construct an isomorphism of the corresponding transformation groupoids and are able to reformulate the open problem of showing invariance of rapid decay under quasi-isometry.

We then begin to examine various notions of amenability when abstracted to measured ́etale groupoids. In the group case, the following properties are equivalent:

1) $G$ is amenable

2) $C_r^∗(G)=C^∗(G)$

3) The trivial representation decends from ^C^∗(G)$ to $C_r^∗(G)$.

In the groupoid, $G$, case we have 1) ⇒ 2) ⇒ 3), but it was shown by Rufus Willett that $C_r^∗(G) = C^∗(G)$ is not enough in general to give amenability of G. In this paper we study property 3) for groupoids, formulate some equivalent statements and show that 3) ⇒ 2) is also false in general.

Kuykendall 210

Draft report

To fulfill the specialty exam requirement, Sarah Berner will give a presentation on “p-adic analogs of the Mandelbrot set” in Keller 403. Please join us if you can.

Title: Universes of sets

Abstract: As is well-known, all mathematical objects can be coded as sets and thereby all of mathematics can be formally founded in set theory. What is perhaps less well-known is that there are many different models of set theory, each of which is powerful enough to function as a universe of sets and found (most) of mathematics, but these models can have very different properties.

This talk will aim to explore the question: what is a model of set theory? We will learn about Skolem’s paradox, that there are countable models of set theory, even though these countable models think they contain uncountable sets like the set of reals. We will be introduced to transitive models, usually considered to be the best behaved, but also meet ill-founded models, such as models which think ZFC is inconsistent. To conclude we will briefly discuss two positions in the philosophy of set theory: universism, the view that there is a unique maximal universe of sets, and multiversism, the view that there are many equally valid universes of sets.

This is an introductory talk, aimed to be understandable by those with little background in set theory. It is a prequel to my next talk, which is in turn a prequel to my talk after that.