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November 2020
Atlantic GR Seminar: Jinzhao Wang (ETH Zurich) and Saikat Mondal (MUN)
Outer entropy equals Bartnik-Bray inner mass, and the gravitational ant conjecture Jinzhao Wang (ETH Zurich) Entropy and energy are found to be closely tied on our quest for quantum gravity. We point out an interesting connection between the recently proposed outer entropy, a coarse-grained entropy defined for a compact spacetime domain motivated by the holographic duality, and the Bartnik-Bray quasilocal mass long known in the mathematics community. In both scenarios, one seeks an optimal spacetime fill-in of a given closed,…
Find out more »Atlantic Graph Theory Seminar: Dr Jared Howell (Memorial University of Newfoundland, Grenfell Campus)
Gracefully labelling windmills using Skolem-like sequences To gracefully label a graph G, assign each vertex v ∊ V(G) a distinct label l(v) from {0,1,2,...,|E(G)|}, such that {|l(u)-l(v)| : uv ∊ E(G)}={1,2,3,...,|E(G)|}. In this talk we will examine constructive techniques using Skolem-like sequences to gracefully label windmills of cycles. This includes new constructive techniques for known results as well as new results on windmills with vanes of mixed cycle length. The Atlantic Graph Theory Seminar series will take place every Wednesday…
Find out more »Dalhousie-AARMS AAMP Seminar: Graham Cox (Memorial University)
Title: Nodal deficiency via equipartition energy functionals and the Dirichlet-to-Neumann map Abstract: A classic result in differential equations is that the nth eigenfunction of a Sturm-Liouville boundary value problem has precisely n-1 zeros. Courant’s nodal domain theorem provides a natural generalization of this result to higher dimensions, but it is generally not sharp. The lack of sharpness is measured by the “nodal deficiency” of an eigenfunction. Despite over a century of intensive study, this quantity is still not very well…
Find out more »December 2020
Atlantic Graph Theory Seminar: Dr Melissa Huggan (Ryerson University)
The Cheating Robot and Insider Information Throughout this talk, we explore a deterministic model as an alternative approach to studying simultaneous play combinatorial games. We call this the Cheating Robot model. This model forces both players to move at the same time, but one player has extra information about where their opponent is going to move and can react accordingly. We discuss some general theory and explore a case study to get some insight into this model. This is joint…
Find out more »Dalhousie-AARMS AAMP Seminar: Peter Hintz (MIT)
Title: Linear stability of slowly rotating Kerr spacetimes Abstract: I will describe joint work with Dietrich Häfner and András Vasy in which we study the asymptotic behavior of linearized gravitational perturbations of Schwarzschild or slowly rotating Kerr black hole spacetimes. We show that solutions of the linearized Einstein equation decay at an inverse polynomial rate to a stationary solution (given by an infinitesimal variation of the mass and angular momentum of the black hole), plus a pure gauge term. The proof uses…
Find out more »Atlantic Graph Theory Seminar: Dr Erin Meger (Université du Québec à Montréal)
The Iterated Local Model for Social Networks Complex networks are said to exhibit four key properties: large scale, evolving over time, small world properties, and power law degree distribution. The Preferential Attachment Model (Barab´asi–Albert, 1999) and the ACL Preferential Attachment Model (Aiello, Chung, Lu, 2001) for random networks, evolve over time and rely on the structure of the graph at the previous time step. Further models of complex networks include: the Iterated Local Transitivity Model (Bonato, Hadi, Horn, Pralat, Wang,…
Find out more »AARMS COVID-19 Seminar: Ali Gharouni (McMaster)
COVID-19 Outbreak Dynamics and Testing-Isolation Efficacy; Insights from a Simple Epidemic Model One of the main challenges in understanding COVID-19 dynamics is to estimate changes in the total level of infection in a population. The daily case count is a highly accessible form of data where observations are driven by two types of processes: (i) epidemic processes and (ii) testing processes. The challenge is then to separate these processes and understand how they interact. We developed a model that incorporates…
Find out more »January 2021
Atlantic Graph Theory Seminar: Dr Stephen Finbow, Saint Francis Xavier University
The γ-graph of a graph For a graph G = (V, E), the γ-graph of G, G(γ) = (V (γ), E(γ)), is the reconfiguration graph whose vertex set is the collection of minimum dominating sets, or γ-sets of G, and two γ-sets are adjacent in G(γ) if they differ by a single vertex and the two different vertices are adjacent in G. The γ-graph of G was introduced by Fricke et al. in 2011 where they studied properties of γ-graphs,…
Find out more »Atlantic Graph Theory Seminar: Dr. Hugh Thomas, UQAM
Dynamical algebraic combinatorics and independence sets of graphs Dynamical algebraic combinatorics is a relatively new (and fun!) topic, which looks at cyclic group actions on objects from algebraic combinatorics, inspired by some questions coming from dynamical systems. I will give an introduction to the area, focusing on an action I have defined with Nathan Williams on the independent sets of a graph (arXiv:1805.00815). We also construct a partial order on the set of independent sets of a graph, which may…
Find out more »Dalhousie-AARMS AAMP Seminar: Allan Greenleaf (Rochester)
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 attend, please email the organizers for connection details.
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