Department of

# Mathematics

Seminar Calendar
for events the day of Thursday, October 18, 2018.

.
events for the
events containing

Questions regarding events or the calendar should be directed to Tori Corkery.
    September 2018          October 2018          November 2018
Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa
1       1  2  3  4  5  6                1  2  3
2  3  4  5  6  7  8    7  8  9 10 11 12 13    4  5  6  7  8  9 10
9 10 11 12 13 14 15   14 15 16 17 18 19 20   11 12 13 14 15 16 17
16 17 18 19 20 21 22   21 22 23 24 25 26 27   18 19 20 21 22 23 24
23 24 25 26 27 28 29   28 29 30 31            25 26 27 28 29 30
30


Thursday, October 18, 2018

11:00 am in 241 Altgeld Hall,Thursday, October 18, 2018

#### Arithmetic properties of Hurwitz numbers

###### David Hansen (University of Notre Dame)

Abstract: Hurwitz numbers are the "$\mathbf{Q}(i)$-analogue" of Bernoulli numbers; they show a remarkable number of patterns and properties, and deserve to be better-known than they are. I'll discuss some old results on these numbers due to Hurwitz and Katz, and some newer results obtained by four Columbia undergraduates during a summer REU I supervised. No background knowledge will be assumed.

12:30 pm in 464 Loomis,Thursday, October 18, 2018

#### Particle-vortex statistics and the nature of dense quark matter

###### Aleksey Cherman (INT Washington)

Abstract: Dense nuclear matter is expected to be a superfluid. Quark matter, which is expected to appear at higher densities, is also a superfluid. But quark matter turns out to be sharply distinct from a standard superfluid, because it supports Z3-valued particle-vortex braiding phases, and its effective action includes a coupling to a topological quantum field theory. Physically, our results imply that certain mesonic and baryonic excitations have orbital angular momentum quantized in units of ħ/3 in the presence of a superfluid vortex. If Z3 braiding phases and angular momentum fractionalization are absent in lower density hadronic matter, as is widely expected, then the quark matter and hadronic matter regimes of dense QCD must be separated by at least one phase transition. Since the low-density regime is a confined' phase, while the high-density regime is a Higgs' phase due to color superconductivity, our results also have interesting implications for Higgs-confinement complementarity.

2:00 pm in 241 Altgeld Hall,Thursday, October 18, 2018

#### The Fifth Arithmetic Operation

###### Eric Wawerczyk (University of Notre Dame)

Abstract: Martin Eichler is attributed to saying: “There are five elementary operations in Number Theory: addition, subtraction, multiplication, division, and modular forms.” The point of this talk is to demonstrate a variety of amazing arithmetic formulas which can be derived using these five “basic” operations. We will be presenting amazing proofs by Euler, Riemann, and Ramanujan.

3:00 pm in 345 Altgeld Hall,Thursday, October 18, 2018

#### The $Q$-system of type $A_2^{(2)}$

###### Minyan Simon Lin (UIUC)

Abstract: In this talk, I will introduce the $Q$-system of type $A_2^{(2)}$, which is a recursion relation that is satisfied by the characters of certain finite-dimensional $\mathfrak{sl}_2$-modules. I will derive some properties of this system, such as its integrability and Laurent properties, and discuss how these properties have a natural extension to the noncommutative case. If time permits, I will discuss some of the consequences of the properties of the noncommutative $Q$-system of type $A_2^{(2)}$.

4:00 pm in 245 Altgeld Hall,Thursday, October 18, 2018

#### Resonance rigidity for Schrödinger operators

###### Tanya Christiansen (University of Missouri)

Abstract: From a mathematical point of view, resonances may provide a replacement for discrete spectral data for a class of operators with continuous spectrum. Physically, resonances may correspond to decaying waves. This talk will introduce the notion of resonances for Schrödinger operators. We discuss results, both by the speaker and others, related to the rigidity of the set of resonances of a Schrödinger operator on ${\mathbb R}^d$ with potential $V\in L^\infty_c({\mathbb R}^d)$. For example, within this class of operators, is the Schrödinger operator with $0$ potential determined by its resonances? What can we say about other sets of isoresonant potentials?