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September 2020
Dalhousie-AARMS AAMP Seminar: Michael Ward (UBC)
Synchrony and Oscillatory Dynamics for a 2-D PDE-ODE Model of Diffusion-Sensing with Small Signaling Compartments We analyze a class of cell-bulk coupled PDE-ODE models, motivated by quorum and diffusion sensing phenomena in microbial systems, that characterize communication between localized spatially segregated dynamically active signaling compartments or "cells" that have a permeable boundary. In this model, the cells are disks of a common radius and they are spatially coupled through a passive extracellular bulk diffusion field with diffusivity in a bounded…
Find out more »Atlantic GR Seminar: Kam To Billy Chan (MUN)
The Reissner-Nordstrom Near Horizon Geometry is a Tangent Spacetime The near horizon geometry (NHG) of an extremal Reissner-Nordstrom black hole is obtained in conventional global AdS coordinates and in the coordinates of the parent spacetime. Geometrical objects, specifically Killing vectors and spacetime points, are mapped from the boundary and horizon of the NHG into the parent spacetime coordinates. The outcome is that the NHG is a tangent spacetime to the extremal Reissner-Nordstrom black hole’s degenerate horizon and that the degenerate…
Find out more »AARMS COVID-19 Seminar: Karen Phillips (Dept of Health and Wellness, PEI) and Javier Sanchez (Atlantic Veterinary College, UPEI)
The Covid-19 modeling experience in Prince Edward Island Since the beginning of the COVID-19 pandemic, Atlantic Canada and particularly PEI, has experienced a low number of cases with limited community spread. This epidemiological situation has created some unique and challenging opportunities for the modelers to address the questions of interest posed by public health officers. A simple SEIR model was developed to assess the magnitude of the consequences in terms of hospitalizations, PPE, and bed requirements under a set of…
Find out more »October 2020
Dalhousie-AARMS AAMP Seminar: John Toth (McGill University)
Title: Pointwise bounds for joint eigenfunctions of quantum completely integrable (QCI) systems Abstract: I will discuss some recent results on improvements in supremum bounds for joint eigenfunctions of QCI systems together with sharp exponential decay estimates away from the projections of invariant Lagrangian tori (ie. in the microlocally forbidden region). This is joint work with Jeff Galkowski. The Dalhousie-AARMS Analysis-Applied Math-Physics Seminar takes place on Fridays from 4 - 5 pm Atlantic Time over Zoom. If you would like to…
Find out more »Atlantic Graph Theory Seminar: David Pike (Memorial)
Perfect 1-Factorisations A matching in a graph $G$ is a subset $M \subseteq E(G)$ of the edge set of $G$ such that no two edges of $M$ share a vertex. A 1-factor of a graph $G$ is a matching $F$ in which every vertex of $G$ is in one of the edges of $F$. If $G$ is a $\Delta$-regular graph of even order then we can ask whether $G$ admits a 1-factorisation, namely a partition of its edge set into…
Find out more »Dalhousie-AARMS AAMP Seminar: Julie Rowlett (Chalmers, Sweden)
Decisions and Disease Do you usually get a flu shot every year? Do you usually take preventive measures to avoid contracting sexually transmitted infections? It is reasonable to expect that while many people may answer `no‘ to the first question, they may answer `yes‘ to the second question. In recent joint work with my PhD student, Carl-Joar Karlsson, we have discovered a mathematical explanation for these different choices. Here I will explain mathematical models we have developed that combine the…
Find out more »Atlantic Graph Theory Seminar: Dr. Ben Cameron (University of Guelph)
Title: Families of graphs containing only finitely many vertex-critical graphs. In this talk, motivated by algorithmic aspects of graph colouring, we will consider the problem of classifying vertex-critical graphs in families of graphs. We will complete a dichotomy theorem for the number of k-vertex-critical H-free graphs when H is a graph of order four. Our results also reduce the remaining open problem for graphs of all orders to two families of graphs. Toward implementing the corresponding graph colouring algorithms, we then…
Find out more »Dalhousie-AARMS AAMP Seminar: Hari Kunduri (Memorial University)
Title: Geometric inequalities for axisymmetric black holes Abstract: In general relativity, isolated, dynamical black holes arise from asymptotically flat initial data for the Einstein equations. Such data are characterized by invariants such as the ADM mass and angular momentum. When angular momentum is conserved in the evolution, the standard picture of gravitational collapse suggests an inequality relating the ADM mass and angular momentum. Such geometric inequalities have been rigorously proved for axisymmetric, asymptotically flat maximal initial data for the vacuum Einstein…
Find out more »Atlantic GR Seminar: Turkuler Durgut (MUN)
Asymptotically Anti-de Sitter Gravitational Solitons In this talk, I will consider the stability of asymptotically anti-de Sitter gravitational solitons. These are globally stationary, asymptotically (globally) AdS spacetimes with positive energy but without horizons. I will introduce my ongoing project investigating solutions of the linear wave equation in this class of backgrounds. I will provide analytical expressions for the behavior of the scalar field near the soliton bubble and at spatial infinity. The special BPS (supersymmetric) case will then be examined…
Find out more »Atlantic Graph Theory Seminar: Iain Beaton (PhD Candidate, Dalhousie University)
The Average Order of Dominating Sets of a Graph This talk focuses on the average order of dominating sets of a graph. We find the extremal graphs for the maximum and minimum value over all graphs on n vertices, while for trees we prove that the star minimizes the average order of dominating sets. We prove the average order of dominating sets in graphs without isolated vertices is at most 3n/4, but provide evidence that the actual upper bound is…
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