Minicourse: Group Graded Azumaya Algebras and Generic Constructions
2023-02-17 11:00 - 2023-02-22 12:00 UTC | Memorial University (St. John’s Campus), St. John's, Newfoundland and Labrador, Canada
Taught by Professor Eli Aljadeff, Technion University, Israel
The main theme of this mini-course is gradings by finite groups on finite-dimensional algebras. Similar to the classical situation of ungraded algebras, we will be interested in finite-dimensional graded simple algebras and finite-dimensional graded division algebras. An important role is played by a generalization of central simple algebras, called Azumaya algebras.
Our main tool will be polynomial identities and, in particular, graded polynomial identities. This tool will allow us to construct generic graded Azumaya algebras.
In the first lecture of the mini-course, as a part of the motivation to discuss group graded algebras, I will recall some classical topics such as division algebras, Brauer groups, crossed products and Galois cohomology. Then I will introduce G-graded polynomial identities, where G is a finite group, and discuss generic constructions. In particular, for an arbitrary finite-dimensional G-graded simple algebra A over an algebraically closed field F of characteristic 0, I will construct a generic G-graded Azumaya algebra from which one can obtain by specialization all forms of A in the sense of Galois descent.
As a key application, I will discuss the following problem. It is not difficult to see that for any finite group G, finite-dimensional G-graded division algebras are G-graded simple and they remain G-graded simple upon any extension of the field of scalars.
We will be interested in the opposite direction. Unlike the situation in the ungraded case, where the algebras of n × n matrices always admit forms which are division algebras, this is not generally true in the setting of G-graded algebras.
Suppose that A is a finite-dimensional G-graded simple algebra over an algebraically closed field F. One of the goals of these lectures is to provide necessary and sufficient conditions on the graded structure of A under which A admits forms that are G-graded division algebras. In particular we show that A must be a G-graded simple algebra for which the corresponding generic G-graded simple algebra is a G-graded division algebra.
The lectures will be delivered during three time periods, as shown below. They will take place at the St. John’s campus of Memorial University and will be broadcast via Webex. All the times are in Newfoundland Time (NST=UTC-3:30).
Friday, February 17, 11-12 am, room A-1045/1046
Monday, February 20, 11-12 am, room A-1045/1046
Wednesday, February 22, 11-12 am, room A-1045/1046
The lectures will be available online via Webex. Contact the organizer for details

Atlantic Graph Theory Seminar: Isaac McMullin and Ian George, Dalhousie University
2023-03-01 15:30 - 16:30 UTC | Online via Zoom
Speaker 1: Isaac McMullin
Existence of Optimal Split Reliability Polynomials
One of the most common models of robustness of a graph against random failures has all vertices operational, but the edges independently operational with probability p. On one hand, one can ask for the probability that all vertices can communicate (all-terminal reliability) while on the other hand, we can ask that two specific vertices (or terminals) can communicate with each other (two-terminal reliability). While both of these questions have been well-studied, they are both increasing functions of the edge probability. One new approach is split reliability, where for two fixed vertices s and t, we consider the probability that every vertex communicates with one of s or t, but not both. The split reliability of G is a polynomial function of p that for connected graphs is 0 both at p=0 and at p=1. In this presentation, we explore the existence for fixed numbers n>=2 and m>=n-1 of an optimal connected (n,m)-graph G_(n,m) for split reliability, that is, a connected graph with n vertices and m edges for which for any other such graph H, the split reliability of G_(n,m) is at least as large as that of H, for all values of p in [0,1]. Unlike the similar problems for all-terminal and two-terminal reliability, where only partial results are known, we completely solve the issue for split reliability, where we show that there is an optimal (n,m)-graph for split reliability if and only if n<=3, m=n-1, or n=m=4.

Speaker 2: Ian George
Degree Polynomials of Graphs
In this talk we introduce the Degree Polynomial of a graph. This polynomial is defined to be the generating function of the sequence (a_0, a_1, a_2, …) where a_k is the number of vertices of degree k in a graph. Little has been published about this polynomial other than its behaviour under graph operations. We will explore some basic properties of this polynomial, and see what information it encodes about a graph. Then we will discuss the roots of degree polynomials, or degree roots, giving some bounds and density results. Along the way, the degree polynomials and degree roots for certain families of graphs will be highlighted.

The talks will be held in room 227 in the Chase building at Dalhousie, and streamed via zoom
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Meeting ID: 864 1523 0827
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Atlantic Graph Theory Seminar: Lucas Mol, Thomson Rivers University
2023-03-08 15:30 - 16:30 UTC | Online via Zoom
Avoiding additive powers in words
A word is a sequence of symbols taken from some finite alphabet. A square is a word of the form xx, where x is a nonempty word. It is well-known that there are infinite words over an alphabet of size 3 that contain no squares. Suppose now that the alphabet is some finite subset of the integers. An additive square is a word of the form xx’, where x and x’ have the same nonzero length and the same sum. Additive cubes, fourth powers, etc., are defined similarly. We present a method for proving that certain types of infinite words contain no additive k-powers. This is joint work with James Currie, Narad Rampersad, and Jeffrey Shallit.

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Dalhousie-AARMS AAMP Seminar: Katrina Morgan (Northwestern University)
2023-03-10 16:00 - 17:00 (America/Halifax) | Dalhousie University, Halifax, Nova Scotia, Canada
Title + Abstract: TBD
The Dalhousie-AARMS Analysis-Applied Math-Physics Seminar takes place on Fridays from 4 – 5 pm Atlantic Time over either Zoom and/or in Chase 227 depending on the speaker. If you would like to attend, please email the organizers for connection details.

Automorphisms And Derivations In Affine Algebraic Geometry
2023-03-13 - 2023-03-17 | Memorial University (St. John’s Campus), St. John's, Newfoundland and Labrador, Canada
Mini-course by Professor Leonid Makar-Limanov, Wayne University, USA
Brief description of the mini course
After this course you will know the proofs of several classical theorems of Affine Algebraic Geometry. The original proofs of these theorems were quite involved and a much longer course would be needed for their exposition.
In the first lecture we will discuss the theorems of Heinrich Jung and Rudolf Rentschler. The first one describes all invertible transformations of the plane by polynomials and the second all generalized shifts of the plane. Algebraically speaking, Jung’s theorem describes all automorphisms of the ring of polynomials with two variables and Rentschler theorem describes all subgroups of this group which are isomorphic to the group of complex numbers under addition. If we have time, we will discuss the groups of polynomial automorphisms of several other surfaces.
The second lecture is devoted to the following topic: if a cylinder is given, is it possible to recover the base of this cylinder. In general the answer is no, but we discuss two cases when this is possible. We show that if the cylinder over a curve is given then we can recover this curve (this is the theorem of Shreeram Abhyankar, Paul Eakin, and William Heinzer). If the cylinder over a surface is isomorphic to a three-dimensional space then the surface is isomorphic to a plane (this is a theorem of Takao Fujita).
Here is an algebraic translation:
If A is an integral domain of transcendence degree one and A[x1, x2,…, xn] is given, we can recover A up to an isomorphism. If A is an integral domain of transcendence degree two and A[x] is isomorphic to C[y1,y2,y3] then A is isomorphic to C[z1,z2]. The main tool used in these two lectures is locally nilpotent derivations.
In the third lecture we prove one of the most famous theorems in affine algebraic geometry, the AMS Theorem (after Abhyankar, Tsuong-tsieng Moh, Masakazu Suzuki): any smooth “good” embedding of a line to a plane is the image of a coordinate line under an automorphism of the plane. Algebraically, this means the following: if two polynomials f(t), g(t)∈ C[t] generate C[t] then the smaller of the degrees of f(t), g(t) divides the larger of the degrees of f(t), g(t). The main tool here is a new algorithm for finding an irreducible dependence between two polynomials in one variable.
The lectures will be delivered during three time periods, as shown below. They will take place at the St. John’s campus of Memorial University and will be broadcast via Webex. All the times are in Newfoundland Time (NST=UTC-3:30).
Monday, March 13th: TBA
Tuesday, March 14th: TBA
Thursday, March 16th: TBA
The lectures will be available online via Webex. The details will be given later. Contact the organizers for more information: Mikhail Kotchetov <mikhail@mun.ca>; Yuri A Bakhturin <bahturin@mun.ca>

Atlantic Graph Theory Seminar: Caleb Jones and Rylo Ashmore (Memorial University)
2023-03-15 15:30 - 16:30 UTC | Online via Zoom
Speaker 1: Caleb Jones, Memorial University

Title: Extending Graph Burning to Hypergraphs

Abstract:
We introduce a round-based model much like graph burning which applies to hypergraphs. The rules for this new model are very natural,and generalize the original model of graph burning. We also introduce a variant called lazy hypergraph burning, along with a new parameter, the lazy burning number. Interestingly, lazily burning a graph is trivial, while lazily burning a hypergraph can be quite complicated. Moreover, the lazy burning model is a useful tool for analyzing the round-based model on hypergraphs. We obtain bounds on the burning number and lazy burning number of a hypergraph in terms of its parameters.

Speaker 2: Rylo Ashmore, Memorial University

Title: Herding Cats Stuck in Trees.

Abstract:
In the game of Cat Herding on a graph, one player (the herder) will omnipresently delete edges, while the other player (the cat) is on a vertex of the graph, and will move along any path to a new vertex. Eventually, the cat is isolated on a single vertex, and the cat’s objective is to delay this event, while the herder tries to hasten it. In an optimally played game, the number of cuts the herder made to isolate the cat is the cat number of the graph. In this talk, we will investigate this graph parameter for both dense and sparse graphs. We will see an argument that the asymptotic behaviour of the cat number of complete graphs is n^2/3. We also look at an unexpected connection between cat herding on trees and Fibonacci numbers. In particular, we will see that trees with maximum cat number amongst graphs with n vertices have cat number asymptotically log_φ (n).

Zoom link: https://us02web.zoom.us/j/86415230827?pwd=[REDACTED]

Meeting ID: 864 1523 0827
Passcode: [REDACTED]

Dalhousie-AARMS AAMP Seminar: Milivoje Lukic (Rice U.)
2023-03-17 16:00 - 17:00 (America/Halifax) | Dalhousie University, Halifax, Nova Scotia, Canada
Title: Universality limits for orthogonal polynomialsAbstract: It is often expected that the local statistical behavior ofeigenvalues of some system depends only on its local properties; forinstance, the local distribution of zeros of orthogonal polynomials shoulddepend only on the local properties of the measure of orthogonality. Thisphenomenon is studied using an object called the Christoffel-Darbouxkernel. The most commonly studied case is known as bulk universality,where the rescaled limit of Christoffel-Darboux kernels converges to thesine kernel.In this talk, we will survey this subject, prior results, and a recentresult which gives for the first time a completely local sufficientcondition for bulk universality. The new approach is based on a matrixversion of the Christoffel-Darboux kernel and the de Branges theory ofcanonical systems, and it applies to other self-adjoint systems with 2×2transfer matrices such as continuum Schrodinger and Dirac operators.The talk is based on joint work with Benjamin Eichinger (TechnicalUniversity Wien) and Brian Simanek (Baylor University).
The Dalhousie-AARMS Analysis-Applied Math-Physics Seminar takes place on Fridays from 4 – 5 pm Atlantic Time over either Zoom and/or in Chase 227 depending on the speaker. If you would like to attend, please email the organizers for connection details.

Atlantic Graph Theory Seminar: Mohammad Salavatipour, U. Alberta
2023-03-22 15:30 - 16:30 UTC | Online via Zoom
Approximation Schemes for Resource Minimization for Fire Containment
Resource Minimization Fire Containment (RMFC) is a natural model for optimal inhibition of
harmful spreading phenomena on a graph. In the RMFC problem on trees, we are given an undirected
tree G, and a vertex r where the fire starts at, called root. At each time step, the firefighters
can protect up to B vertices of the graph while the fire spreads from burning vertices to all their
neighbors that have not been protected so far. The task is to find the smallest B that allows for
saving all the leaves of the tree. The problem is hard to approximate up to any factor better than 2
even on trees unless P = NP.
In this talk we present an asymptotic QPTAS for RMFC on trees. More specifically, let eps > 0,
and F be an instance of RMFC where the optimum number of firefighters to save all the leaves is
OPT(F). We present an algorithm which uses at most ceil(1 + eps )OPT(F)rceil many firefighters at each
time step and runs in time n^O(loglog n). This suggests that the existence of an asymptotic PTAS is
plausible especially since the exponent is O(log log n).
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Atlantic Graph Theory Seminar: Calum MacRury, University of Toronto
2023-03-29 15:30 - 16:30 UTC | Online via Zoom
Approximation Schemes for Resource Minimization for Fire Containment
The semi-random graph process is an example of an adaptive process for constructing a graph in which random edges are added step by step. It is adaptive in that there is an online algorithm which has partial control over which random edges are added. Through intelligent decision-making, the objective of the algorithm is to force the graph to satisfy a fixed graph property with high probability in as few rounds as possible. We first provide upper and lower bounds on the performance of an optimal algorithm when the property corresponds to being Hamiltonian or to containing a perfect matching. This part of the talk is based on joint works with Pawel Pralat and Jane Gao.Afterwards, we introduce a formal definition of an adaptive random graph process which generalizes both the semi-random graph process, as well as the Achlioptas process. In this model, we define a condition called edge-replaceability which we prove is sufficient for a property to have a sharp threshold. Intuitively, a property has a sharp threshold if the optimal algorithm’s “success probability” transitions from almost $0$ to almost $1$ in a negligible number of steps. We apply our result to the semi-random graph process to show that the properties of being Hamiltonian and of containing a perfect matching each have a sharp threshold. This part of the talk is based on a joint work with Erlang Surya.

Dalhousie-AARMS AAMP Seminar: Erick Schulz (ETH Zürich)
2023-03-31 16:00 - 17:00 (America/Halifax) | Dalhousie University, Halifax, Nova Scotia, Canada

Topological Quantum Field Theory Spring School
2023-05-01 - 2023-05-05 | Old Orchard Inn and Conference Centre, 153 Greenwich Road S., Wolfville, Nova Scotia, Canada
Topological Quantum Field Theory lives at the intersection of category theory, algebraic topology, representation theory, and theoretical physics. Physically, TQFTs describe and control the symmetries of quantum systems, including quantum symmetries, anomalous symmetries, and higher-form symmetries. Mathematically, TQFTs provide a dictionary between manifold topology and structures in representation theory, and as such allow computations and results to move between these separate fields. This school, aimed at math PhD students from Atlantic Canada, will consist of three 5-hour minicourses related to TQFTs, plus problem sessions and discussion time; students are expected to be familiar with the basic language of category theory, but are not expected to have any specialized knowledge in the field. The minicourses will be: Factorization Algebras (Araminta Amabel); Spectral Sequences (Arun Debray); Fusion Categories (Colleen Delaney).

East Coast Combinatorics Conference 2023
2023-05-10 - 2023-05-11 | Acadia University, Wolfville, Nova Scotia, Canada
The East Coast Combinatorics Conference is a 2-day annual event that brings together researchers in graph theory, design theory, and other areas of combinatorics. There will be two plenary speakers, and a number of contributed talks, in addition to opportunities for collaboration. The event brings together established researchers and those in the early stages of their academic careers and provides opportunities for subsequent collaborative research projects. We encourage participation by students since they greatly benefit from the opportunity to meet and interact with their peers across the region, as well as to hear about the many and varied research interests of faculty.

Canadian Discrete and Algorithmic Mathematics conference
2023-06-05 - 2023-06-08 | Winnipeg, Manitoba, Canada
The Canadian Discrete and Algorithmic Mathematics (CanaDAM) is the pre-eminent conference in its area in Canada. It has been
held every two years since its founding in 2009. The general topic of the conference is the theory and application of
discrete structures; the goal is to highlight the most salient trends in the field. CanaDAM will bring together researchers
from the various disciplines with which discrete and algorithmic mathematics interact. Particular areas of interest include
graphs and digraphs, hypergraphs, matroids, ordered sets, designs, coding theory, enumeration, combinatorics of words,
discrete optimization, discrete and computational geometry, lattice point enumeration, combinatorial algorithms,
computational complexity, and applications of discrete and algorithmic mathematics, such as web graphs, computational
biology, telecommunication networks, and information processing. CanaDAM strongly encourages participation from students and
postdocs. We hope to see you there!

Theory Canada 15
2023-06-16 - 2023-06-18 | Mount Allison University, Sackville, New Brunswick, Canada
Theory Canada is an annual meeting which brings together Canadian theorists from across the country in order to foster collaborations and exchange of ideas across the disciplines of theoretical physics. It is organized by the Division of Theoretical Physics of the Canadian Association of Physicists (CAP). Theory Canada 15 will be held at Mount Allison University from June 16-18, 2023, just before the main CAP meeting which will be in Fredericton.

Junior Math and Computer Science Camp
2023-07-10 - 2023-07-14 | Acadia University, Wolfville, Nova Scotia, Canada
This week-long day camp is an opportunity for students entering grades 5 or 6 in the Annapolis Valley to participate in fun and enriching science-based activities with Acadia faculty and students to develop their curiosity and enjoyment of math and computer science. It represents an important piece of a multi-year plan to develop the science skills of young students in the Annapolis Valley by bringing young students into the Acadia University outreach program. This will begin the process of positively engaging students with math and computer science at a critical time in their education. Bursaries are provided for those who qualify for financial assistance.

29th Workshop on Logic, Language, Information and Computation
2023-07-11 - 2023-07-14 | Dalhousie University, Halifax, Nova Scotia, Canada
WoLLIC is an annual international forum on inter-disciplinary research involving formal logic, computing and programming theory, and natural language and reasoning. Each meeting includes invited talks and tutorials as well as contributed papers. The 29th WoLLIC will be held at Dalhousie University in Halifax, Nova Scotia, Canada, July 11–14, 2023. The conference typically covers the following topics: foundations of computing, programming and Artificial Intelligence (AI); novel computation models and paradigms; broad notions of proof and belief; proof mining, type theory, effective learnability and explainable AI; formal methods in software and hardware development; logical approach to natural language and reasoning; logics of programs, actions and resources; foundational aspects of information organization, search, flow, sharing, and protection; foundations of mathematics; philosophical logic; philosophy of language.

Bridges Halifax 2023
2023-07-27 - 2023-07-31 | Dalhousie University, Halifax, Nova Scotia, Canada
This conference is the premier international, interdisciplinary conference connecting mathematics and art. The goal of the Bridges meetings is to foster research, practice, and new interest in mathematical connections to art, music, architecture, education and culture. All too often, mathematics can seem disconnected from or even antithetical to these other topics. We believe that mathematics and art can inform and enrich each other, that there are great ideas waiting to be found in the mathematical analysis of art, and that artistic thinking and activities can enliven what we understand about mathematics.
The Bridges conference brings together an interdisciplinary group of mathematicians, scientists, engineers, artists, educators, musicians, writers, computer scientists, sculptors, dancers, weavers, model builders and many others in an atmosphere of mutual exchange and inspiration.

Public Lecture: The hat, the turtle and the spectre
2023-07-27 20:00 - 21:30 UTC | Dalhousie University, Halifax, Nova Scotia, Canada
Come hear about the recent solution to a longstanding unsolved problem in geometry: it is possible for a single shape to tile the plane without any sort of repeating pattern? The “hat”, it turns out, solves this problem. It’s the first known aperiodic monotile, also known as an “Einstein”. In this public lecture, Craig Kaplan from the University of Waterloo (a member of the collaboration that discovered the “hat”), will talk about some background concepts from tiling theory and the history of the search for aperiodic shapes. The story of this discovery of the hat and the proof of its aperiodicity, as well as two other closely related shapes, the “turtle” and the “spectre”, will dazzle you with their application to derive more results about aperiodic tilings.
This talk will be in the Irving Oil Auditorium in the Richard Murray Design Building on Thursday, July 27 from 8:00 pm – 9:30 pm.
Read more about the recent discovery of the aperiodic monotile:

Elusive ‘Einstein’ Solves a Longstanding Math Problem (New York Times)
Newfound Mathematical ‘Einstein’ Shape Creates a Never-Repeating Pattern (Scientific American)
‘The miracle that disrupts order’: mathematicians invent new ‘einstein’ shape (The Guardian)
Mathematicians say they have invented an ‘impossible’ tile that never repeats (CTV news)

Bridges Math and Art Family Day
2023-07-30 13:00 - 17:30 UTC | Halifax Central Library
AARMS would like to invite everyone to the Bridges 2023 Math and Art family day! This exciting event is part of the Bridges 2023 conference on Math and Art, and will be held at the Halifax Central Library on Sunday, July 30 from 1:00 pm to 5:30 pm. Family day incorporates hands-on workshops, mathematical poetry reading, a short film festival, and a mathematical art exhibition in the nearby Medjuck Building on Dalhousie’s Sexton Campus.

6th International Conference on Applied Category Theory
2023-07-31 - 2023-08-04 | University of Maryland, college Park, MD, United States
Established in 2018, the annual International Conference on Applied Category Theory brings together researchers, programmers, scientists and industry who seek to apply the foundational field of category theory to fields outside of mathematics. The ACT Adjoint School is annual research school adjoining the conference. The research school is aimed at fostering an open-hearted and open-minded environment where new applied category theorists develop the skills of research, welcoming new researchers into cutting-edge research programs in applied category theory, and to grow and strengthen the applied category theory community. The research school convenes online once every two weeks for 4 months before the conference and concludes research projects during the in-person research week before the conference.

2nd workshop of AARMS CRG on Mathematical Foundations of Scientific Machine Learning
2023-07-31 - 2023-08-01 | University of New Brunswick (Fredericton Campus), Fredericton, New Brunswick, Canada
This is the 2nd workshop of the AARMS Collaborative Research Group on Mathematical Foundations in Scientific Machine Learning, which will be held on the Fredericton Campus of the University of New Brunswick on Jul 31 – Aug 01, 2023.
The theme of the workshop is as broad as the scientific research programs of the partners in the AARMS CRG group, including Machine Learning approaches in Mathematics, Geophysics, Chemistry, Statistics, etc.

Groups, Rings, Lie and Hopf Algebras. Fifth Edition
2023-08-21 - 2023-08-27 | Memorial University (Harlow Campus), 44 Market Street, Harlow, United Kingdom
Our next International workshop “Groups, Rings, Lie and Hopf Algebras. V” will be held at the Harlow campus of Memorial University in the United Kingdom on August 21 – 27, 2022. This is the first time the venue of our workshop will be outside North America. The web site of their campus is here.
The organizing committee consists of Yuri Bahturin (Memorial University), Mikhail Kotchetov (Memorial University), Kirill Zaynullin (University of Ottawa), and Alexander Premet (University of Manchester).
A preliminary list of speakers includes:

Aljadeff, Eli (Technion)
Ara, Pere (Universitat Autònoma de Barcelona)
Baird, Tom (Memorial University)
Baranov, Alexander (University of Leicester)
Billig, Yuly (Carleton University)
Brzeziński, Tomasz (Swansea University)
Elduque, Alberto (Universidad de Zaragoza)
Jespers, Eric (Vrije Universiteit Brussel)
Martinez-Pedroza, Eduardo (Memorial University)
Minasyan, Ashot (University of Southampton)
Neher, Erhard (University of Ottawa)
Schweigert, Christoph (University of Hamburg)
Sierra, Susan (University of Edinburgh)
Shpektorov, Sergei (University of Birmingham)
Smoktunowicz, Agata (University of Edinburgh)
Sommerhäuser, Yorck (Memorial University)
Traustason, Gunnar (University of Bath)
Vaughan-Lee, Michael (University of Oxford)
Zalesski, Alexandre (University of East Anglia)

The workshop is organized in the framework of the collaborative research group “Groups, Rings, Lie and Hopf Algebras” of the Atlantic Association for Research in the Mathematical Sciences (AARMS). An updated list of speakers and other information will be posted on this page.
If you are interested in attending the workshop, please send an email to this address (aac@mun.ca) with GRLHA23 in the subject line by May 15, 2023. If you would like to give a talk, please include the title and abstract.
There are limited funds available to cover accommodation on the Harlow campus. If you would like to request this support, please write to aac@mun.ca; if you are not a member of the collaborative research group, please attach your CV.

Atlantic Graph Theory Seminar
2023-09-20 15:30 - 16:30 UTC | Online via Zoom
Time: 3.30pm, Atlantic time, Wednesday Sept.20
Speaker: Jessica McDonald, Auburn University

Title: On flows (and group-connectivity) in signed graphs
Abstract:

In this talk we’ll start by discussing flows in signed graphs and how it generalizes the usual notion of integer flows in graphs. In particular, flow-colouring duality of graphs in the plane can be re-interpreted using signed graphs in the projective plane. Also, where a flow in a graph can be viewed as a sum of flows on cycles, in a signed graph, positive cycles and barbells are the key structures to consider. We’ll share a new result, joint with K. Nurse and A. Brewer-Castano, about flows in 3-edge-connected signed graphs. In fact, this result holds for the stronger notion of group-connectivity, which was introduced as a generalization of flows by Jaeger, Linial, Payan, and Tarsi in 1992. Building on their work and also on work by Li, Luo, Ma and Zhang (2018), we (mostly) establish a group-connected analog of Seymour’s 6-flow Theorem for signed graphs.

Zoom link:
https://us02web.zoom.us/j/86415230827?pwd=[REDACTED]

Meeting ID: 864 1523 0827
Passcode: [REDACTED]

Atlantic Graph Theory Seminar
2023-10-04 15:30 - 16:30 UTC | Online via Zoom
Speaker: Iain Beaton, Acadia University
Title: On the Unimodality of Nearly-Well Dominated Trees

Abstract: A polynomial is said to be unimodal if its coefficients are non-decreasing and then non-increasing. The domination polynomial of a graph G is the generating function of the number of dominating sets of each cardinality in G, and its coefficients have been conjectured to be unimodal. In this talk we will show the domination polynomial of a tree T is unimodal so long as the sizes of the minimal dominating sets of T do not differ by too much. We will also discuss a version of this result for directed trees and its connection to the unimodality conjecture for the independence polynomial of a well-covered tree.

Zoom link:

https://us02web.zoom.us/j/86415230827?pwd=[REDACTED]

Meeting ID: 864 1523 0827
Passcode: [REDACTED]

2023 Science Atlantic MSCS Conference
2023-10-13 - 2023-10-15 | University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada
The Science Atlantic Mathematics, Statistics, and Computer Science Conference is an annual regional event. It provides a platform for undergraduate students in Mathematics, Statistics and Computer Science at Atlantic Canadian universities to disseminate their research projects, participate in contests, and network with other students in the region. It also serves as a networking event for faculty members of Atlantic Canadian universities. In 2023, University of Prince Edward Island will host the conference in Charlottetown, PEI. The dates of the conference is October 13- 15, 2023. Some of the major programs are as follows: Field Lecture, Blundon Lecture, Sedgewick Lecture, Contributed Student’s talks, Mathematics Competition, CS Programming Competition, AARMS Session, Science Atlantic joint Math/CS meeting, Science Atlantic Math and Stats. meeting, Science Atlantic CS meeting, Graduate Student’s Session etc.

Women in Commutative Algebra II
2023-10-16 - 2023-10-20 | Trento, Trento, Italy
The purpose of this event is to establish and enhance research networks among women and female identifying mathematicians who work in the areas of mathematics related to commutative algebra. It will be the second of its kind. The first one (Banff 2019) was an amazing success, with many of the groups still working together. It has led to a strong network that besides research, provides visibility for women and many opportunities for professional development. It has also served as an example for younger women. We are hoping that WICA II, with its European location, will be more accessible to a larger geographic area.
We need general funds, as most of the sources we apply to are targetted to special regions. Any support from AARMS will be appreciated. If we do not raise enough funds, the event will go ahead but we will have to reduce the number of participants.

Atlantic Graph Theory Seminar
2023-10-18 15:30 - 16:30 UTC | Online via Zoom
Two short talks by grad students Alex Clow and William Kellough. ‘Live’ viewing in Chase 227 for those at Dalhousie.
Talk 1:
Alex Clow, Simon Fraser University
Polynomially Bounding the Oriented Chromatic Number in Euler Genus
In this talk we consider the oriented chromatic number of graphs with bounded Euler genus. In particular, we present our proofs that the oriented chromatic number is at most $g^{6400}$ for sufficiently large $g$ and at least $Omega((frac{g^2}{log g})^{1/3})$. This is a major improvement over the previous best upper bound which is exponential in genus. We conclude the talk by discussing directions for future study. Joint work with Peter Bradshaw and Jingwei Xu from the University of Illinois at Urbana Champaign.
Talk 2:
William Kellough, Memorial University
How to Catch a Cheating Robber on Strong Products
Cops and Robbers is a pursuit-evasion game played on the vertices of a graph. One player controls a set of cops and the other player controls a robber. The cops win if a cop can move to the vertex occupied by the robber in finitely many turns, otherwise the robber wins. In this talk, we consider a variation of Cops and Robbers where both players move simultaneously and the robber “cheats” by knowing how the cops will move each round. We will give bounds on the minimum number of cops needed to win this game when played on the strong product of two graphs. This is joint work with Nancy Clarke and Danny Dyer.
Join Zoom Meeting
https://us02web.zoom.us/j/86415230827?pwd=[REDACTED]

Atlantic Graph Theory Seminar
2023-11-01 15:30 - 16:30 UTC | Online via Zoom
Detecting (Di)Graphical Regular Representations
Speaker: Joy Morris, U. Lethbridge
Abstract: Graphical and Digraphical Regular Representations (GRRs and DRRs) are a concrete way to visualise the regular action of a group, using (di)graphs. More precisely, a GRR or DRR on the group $G$ is a (di)graph whose automorphism group is isomorphic to the regular action of $G$ on itself by right-multiplication.

For a (di)graph to be a DRR or GRR on $G$, it must be a Cayley (di)graph on $G$. Whenever the group $G$ admits an automorphism that fixes the connection set of the Cayley (di)graph setwise, this induces a nontrivial graph automorphism that fixes the identity vertex, which means that the (di)graph is not a DRR or GRR. Checking whether or not there is any group automorphism that fixes a particular connection set can be done very quickly and easily compared with checking whether or not any nontrivial graph automorphism fixes some vertex, so it would be nice to know if there are circumstances under which the simpler test is enough to guarantee whether or not the Cayley graph is a GRR or DRR. I will present a number of results on this question.

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https://us02web.zoom.us/j/86415230827?pwd=[REDACTED]

Atlantic Graph Theory Seminar
2023-11-22 15:30 - 16:30 UTC | Online via Zoom
Speaker: Santiago Guzman-Pro, TU Dresden
Title: Forbidden Tournaments and the Orientation (Completion) Problem

Abstract: For a fixed finite set of oriented graphs F, the F-free orientation problem asks
whether a given finite undirected graph G has an F-free orientation, i.e., whether the edges
of G can be oriented so that the resulting oriented graph does not contain any oriented
graph from F as an oriented (induced) subgraph. It was first noted by Bang-Jensen, Huang,
and Prisner that when F is a set of oriented paths on 3 vertices, this problem easily reduces
to 2-SAT, and thus is solvable in polynomial-time. This was later extended to sets of oriented
graphs on 3 vertices (G.P. and Hernández-Cruz 2017). Towards a complete understanding
of the complexity of the F-free orientation problem, we consider the case when F is a set of
finite tournaments. We prove that for every such F, this problem is in P or NP-complete.Specifically, we show that either the F-free orientation problem can be reduced (in polynomial-
time) to a system of Boolean linear equations, or the F-free orientation problem is NP-complete.
This dichotomy result is accompanied by a classification statement which, given a set of
tournaments F, allows us to decide whether the F-free orientation problem is in P or
NP-complete. We reduce this classification task to a complete complexity classification of the
orientation completion problem for F, which is the variant of the problem above where the input
is a partially oriented graph instead of an undirected graph, introduced by Bang-Jensen, Huang,
and Zhu (2017). Our proof uses results from the theory of constraint satisfaction, and a result
of Agarwal and Kompatscher (2018) about infinite permutation groups and transformation monoids.

This is joint work with Manuel Bodirsky.

University of New Brunswick Data Challenge 2023
2023-11-24 | University of New Brunswick (Fredericton Campus), Fredericton, New Brunswick, Canada
The UNB Data Challenge 2023 will bring together two competitive tracks, Data Visualization (8th Annual), and Data Analytics (4th Annual) on Nov. 24, 2023, in a virtual format! Take up the challenge and demonstrate the power of data.
Participants and teams will have the chance to showcase their ability to tell a story driven by data in unique competitive formats. Teams can participate in both tracks. It is an ideal setting for citizens to get engaged, meet leaders in academia, government, and private organizations, and explore the world of data science.
