## Archived seminars in MathematicsSeminars 1 to 50 | Next 50 seminars |

### Christian Lubich

*Mathematisches Institut Universitaet Tuebingen*

Date: Tuesday 12 November 2019

### Yiming Ma

*Mathematics and Statistics, University of Otago*

Date: Tuesday 8 October 2019

### Phillip Wilcox

*Mathematics and Statistics, University of Otago*

Date: Thursday 3 October 2019

### Tom McCone

*Department of Mathematics and Statistics*

Date: Tuesday 1 October 2019

### Paul Gardner

*Department of Biochemistry, Otago*

Date: Tuesday 24 September 2019

### Travis Scrimshaw

*University of Queensland*

Date: Tuesday 17 September 2019

### Radek Erban

*University of Oxford*

Date: Tuesday 10 September 2019

### Ronald Peeters

*Economics Department*

Date: Tuesday 3 September 2019

### Jinge Lu

*Otago Computer Science*

Date: Tuesday 20 August 2019

### Fabien Montiel

*Department of Mathematics and Statistics*

Date: Tuesday 13 August 2019

### Dmitry Jakobson

*McGill University*

Date: Tuesday 6 August 2019

### Steven Mills

*Department of Computer Science*

Date: Tuesday 30 July 2019

### Zach Weber

*Philosophy Department University of Otago*

Date: Tuesday 23 July 2019

### Arkadii Slinko

*Department of Mathematics. University of Auckland*

Date: Tuesday 9 July 2019

### Leo Tzou

*University of Sydney*

Date: Tuesday 11 June 2019

### Florian Beyer

*Mathematics and Statistics, University of Otago*

Date: Tuesday 28 May 2019

### Brendan Creutz

*School of Mathematics and Statistics, University of Canterbury*

Date: Tuesday 14 May 2019

### Michael Albert

*University of Otago Computer Science*

Date: Tuesday 7 May 2019

### Geertrui van de Voorde

*School of Mathematics and Statistics University of Canterbury*

Date: Tuesday 16 April 2019

### Sarah Wakes

*Department of Mathematics and Statistics*

Date: Tuesday 9 April 2019

### Tim Candy

*Department of Mathematics and Statistics*

Date: Tuesday 2 April 2019

### Conor Finnegan

*University College Dublin*

Date: Tuesday 26 March 2019

### Andrew Robinson

*University of Melbourne*

Date: Thursday 21 March 2019

### Lech Szymanski

*Department of Computer Science, University of Otago*

Date: Tuesday 19 March 2019

### Robert van Gorder

*Department of Mathematics and Statistics, University of Otago*

Date: Tuesday 12 March 2019

These conditions generalize a variety of results known in the literature, such as the algebraic inequalities commonly used as sufficient criteria for the Turing instability on static domains, and approximate or asymptotic results valid for specific types of growth, or for specific domains.

### Russell Higgs

*School of Mathematics and Statistics, University College Dublin*

Date: Tuesday 5 March 2019

### Alex Gavryushkin

*Department of Computer Science University of Otago*

Date: Tuesday 16 October 2018

### Marnus Stoltz

*Department of Mathematics and Statistics*

Date: Tuesday 9 October 2018

### Nikola Stoilov

*University of Burgundy*

Date: Tuesday 25 September 2018

### Mike Hendy

*Department of Mathematics and Statistics*

Date: Tuesday 18 September 2018

$|a_{ij} |≤1,∀i,j⟹|det(A) |≤n^{(n⁄2)}$,

and found matrices satisfying this bound for many values of $n$.

An $n×n$ real matrix $A=(a_{ij})$ with entries $|a_{ij}|≤1$ satisfying

$| det(A)|=n^{(n∕2)}$

is now referred to as a Hadamard matrix. We will see that for $n≥4$, Hadamard matrices can exist only for $n≡0$ (mod 4). Although there are Hadamard matrices for an infinite number of multiples of 4, the Hadamard conjecture that postulates there exists a Hadamard matrix of order $n$, for each positive integer multiple of 4, has remained unresolved for 125 years.

In this talk I will present some practical applications of Hadamard matrices, including my own discovery of their application in phylogenetics, and reveal a personal encounter with Hadamard's ghost.

### Alex Gavryushkin

*Department of Computer Science*

Date: Tuesday 11 September 2018

### Chris Stevens

*Rhodes University, South Africa*

Date: Tuesday 4 September 2018

We are now in the exciting new era of gravitational wave astronomy, where we can study the universe through the gravitational waves emitted by massive events such as coalescing black holes or neutron stars.

An important part of gravitational wave astronomy is the numerical simulations that compute the emitted gravitational radiation, which are non-trivial since the simulations are on a physical domain of finite extent but gravitational waves are unambiguously defined only at future null infinity (scri+). There are a number of methods for waveform estimation, but only in characteristic extraction is the waveform calculated at scri+.

We present a new algorithm and implementation of characteristic extraction. It has the key feature of being simply extendable to characteristic matching, in which the characteristic evolution provides outer boundary data for the "3+1" simulation. The key advantage of characteristic matching is that it would lead to a significant speed-up in the time required to complete a numerical simulation.

### Melissa Tacy

*Department of Mathematics and Statistics*

Date: Tuesday 21 August 2018

### Dominic Searles

*Department of Mathematics and Statistics*

Date: Tuesday 14 August 2018

### David Bryant

*Department of Mathematics and Statistics*

Date: Thursday 9 August 2018

### Ilija Tolich

*Department of Mathematics and Statistics*

Date: Tuesday 31 July 2018

The Baumslag-Solitar group is an example of an amenable quasi-lattice ordered group. In particular, it is an HNN-extension of the integers. Studying the Baumslag-Solitar group gave us the insight to prove a new means of detecting amenability in quasi-lattice ordered groups and also to construct new examples of amenable quasi-lattice ordered groups.

### Dominic Searles

*Department of Mathematics and Statistics*

Date: Tuesday 29 May 2018

In joint work with Assaf, we consider the application of Kohnert's algorithm to arbitrary box diagrams in the positive quadrant; we call the resulting polynomials Kohnert polynomials. We establish some structural results about Kohnert polynomials, including that their stable limits are quasisymmetric. Certain choices of box diagrams yield bases of the polynomial ring in a natural way; as an application, we use these results to introduce a new basis of polynomials whose stable limit is a new basis of quasisymmetric functions that contains the Schur functions. Some further conjectures regarding Kohnert polynomials will be presented.

### Honours and PGDip students

*Department of Mathematics and Statistics*

Date: Friday 25 May 2018

Qing Ruan : ~~Bootstrap selection in kernel density estimation with edge correction~~

Willie Huang : ~~Autoregressive hidden Markov model - an application to tremor data~~

MATHEMATICS

Tom Blennerhassett : ~~Modelling groundwater flow using Finite Elements in FEniCS~~

Peixiong Kang : ~~Numerical solution of the geodesic equation in cosmological spacetimes with acausal regions~~

Lydia Turley : ~~Modelling character evolution using the Ornstein Uhlenbeck process~~

Ben Wilks : ~~Analytic continuation of the scattering function in water waves~~

Shonaugh Wright : ~~Hilbert spaces and orthogonality~~

Jay Bhana : ~~Visualising black holes using MATLAB~~

### Boris Daszuta

*Department of Mathematics and Statistics*

Date: Tuesday 22 May 2018

In particular, assuming a moment in time symmetry in vacuum reduces the problem of solving the constraints to a restriction of zero scalar curvature associated with the initial data set. A result due to [1] at the analytical level provides a technique for local control on the aforementioned set and may be used to engineer initial data with well-defined asymptotics. In short, one may glue together distinct, known solutions from differing regions in a controlled manner forming new data.

The aim of this talk is to demonstrate how a numerical scheme may be fashioned out of the above and present results pertaining to a numerical gluing construction.

Ref:

[1]: (Corvino, J.) Scalar Curvature Deformation and a Gluing Construction for the Einstein Constraint Equations. ~~Communications in Mathematical Physics~~ 214, 1 (2000), 137-189.

### Markus Antoni

*Department of Mathematics and Statistics*

Date: Tuesday 15 May 2018

### Joshua Ritchie

*Department of Mathematics and Statistics*

Date: Tuesday 8 May 2018

### Lettie Roach

*Victoria University Wellington and NIWA*

Date: Tuesday 1 May 2018

### Valerie Isham, NZMS 2018 Forder Lecturer

*University College London*

Date: Tuesday 24 April 2018

In this talk, I will review some stochastic point process-based models constructed in continuous time and continuous space using spatial-temporal examples from hydrology such as rainfall (where flood control is a particular application) and soil moisture. By working with continuous spaces, consistent properties can be obtained analytically at any spatial and temporal resolutions, as required for fitting and applications. I will start by covering basic model components and properties, and then go on to discuss model construction, fitting and validation, including ways to incorporate nonstationarity and climate change scenarios. I will also describe some thoughts about using similar models for wildfires.

### Valerie Isham, NZMS 2018 Forder Lecturer

*University College London*

Date: Monday 23 April 2018

Epidemic models are developed as a means of gaining understanding about the dynamics of the spread of infection (human and animal pathogens, computer viruses etc.) and of rumours and other information. This understanding can then inform control measures to limit spread, or in some cases enhance it (e.g., viral marketing). In this talk, I will give an introduction to simple generic epidemic models and their properties, the role of stochasticity and the effects of population structure (metapopulations and networks) on transmission dynamics, illustrating some past successes and outlining some future challenges.

### Robert Aldred

*Department of Mathematics and Statistics*

Date: Tuesday 17 April 2018

Several attempts at proving the famous 4-colour theorem involved the existence of Hamiltonian cycles in planar graphs related to triangulations of the plane. We will discuss some of these and outline a proof that that the number of Hamiltonian cycles in a 5-connected planar triangulation on $n$ vertices grows exponentially with $n$.

### Mihály Kovács

*Chalmers University of Technology and Gothenburg University*

Date: Tuesday 10 April 2018

### Sergei Fedotov

*The University of Manchester*

Date: Tuesday 27 March 2018

### Yawen Chen

*Department of Computer Science*

Date: Tuesday 20 March 2018

In this talk, I would like to introduce my recent graph-related research problems on Optical Network-on-Chips, which need to be investigated with the knowledge of graph theory and combinatorial optimisation. Feedback and suggestions would be much appreciated from the math department. Below is the background of this research.

Nowadays microprocessor development has moved into a new era of many-core on-chip design, with tens or even hundreds of cores fitting within a single processor chip to speed up computing. However, conventional electrical interconnect for inter-core communication is limited by both bandwidth and power density, which creates a performance bottleneck for microchips in modern computer systems - from smartphones to supercomputers, and to large-scale data centers. Optical Network-on-Chip (ONoC), a silicon-based optical interconnection among cores at the chip level, overcomes the limitations of conventional electrical interconnects by supporting greater bandwidth with less energy consumption, and opens the door to bandwidth- and power-hungry applications. This talk will introduce graph-related research problems on ONoCs from a networking perspective and present our current results and challenging problems for designing efficient multicast routing schemes specific for ONoCs.

### Cornelia Schneider

*University Erlangen-Nuremberg*

Date: Tuesday 13 March 2018

### Bernard Deconinck

*University of Washington*

Date: Tuesday 6 March 2018

I will provide an overview of what is known about the stability of spatially periodic water waves, discussing historically significant results, skipping all mathematical details. Then I will introduce different asymptotic models that are used to describe water waves in different regimes (long waves in shallow water, modulated waves in deep water, etc) and I will discuss how the stability results in this context do or do not make sense compared to those in the context of the full water wave problem.

Time permitting, I will give more detail on recent work to understand the stability of modulated waves in deep water with respect to so-called subharmonic perturbations.