• Counting endomorphisms of crown-like orders 

      Currie, James D.; Visentin, Terry I. (Springer, 2002-12)
      The authors introduce the notion of crown-like orders and introduce powerful tools for counting the endomorphisms of orders of this type.
    • COVID-19’s Second Wave: How are teachers faring with the return to physical schools? 

      EdCan. Well at Work; Ranby, Sarah; Rebeiz, André; Sokal, Laura; Eblie Trudel, Lesley; Babb, Jeff (Canadian Education Network, 2020-11-20)
    • Cyclically t-complementary uniform hypergraphs 

      Gosselin, Shonda (European Journal of Combinatorics, 2010-05)
      A cyclically t-complementary k-hypergraph is a k-uniform hypergraph with vertex set V and edge set E for which there exists a permutation 2 Sym.V/ such that the sets E; E ; E 2; : : : ; E t􀀀1 partition the set of all ...
    • Dejean's conjecture holds for n ≥ 27 

      Currie, James; Rampersad, Narad (EDP Sciences, 2009)
      We show that Dejean’s conjecture holds for n ≥ 27. This brings the final resolution of the conjecture by the approach of Moulin Ollagnier within range of the computationally feasible.
    • A direct proof of a result of Thue 

      Currie, James D. (Utilitas Mathematica, 1984)
    • Extremal words in morphic subshifts 

      Zamboni, Luca Q.; Saari, Kalle; Rampersad, Narad; Currie, James D. (Elsevier, 2014-01-22)
      Given an infinite word x over an alphabet A, a letter b occurring in x, and a total order \sigma on A, we call the smallest word with respect to \sigma starting with b in the shift orbit closure of x an extremal word of ...
    • A family of formulas with reversal of high avoidability index 

      Currie, James; Mol, Lucas; Rampersad, Narad (World Scientific, 2017)
      We present an infinite family of formulas with reversal whose avoidability index is bounded between 4 and 5, and we show that several members of the family have avoidability index 5. This family is particularly interesting ...
    • For each a > 2 there is an Infinite Binary Word with Critical Exponent a 

      Currie, James D.; Rampersad, Narad (The Electronic Journal of Combinatorics, 2008-08-31)
      The critical exponent of an infinite word w is the supremum of all rational numbers α such that w contains an α-power. We resolve an open question of Krieger and Shallit by showing that for each α>2 there is an infinite ...
    • Least Periods of Factors of Infinite Words 

      Currie, James D.; Saari, Kalle (EDP Sciences, 2009)
      We show that any positive integer is the least period of a factor of the Thue-Morse word. We also characterize the set of least periods of factors of a Sturmian word. In particular, the corresponding set for the Fibonacci ...
    • Mathematical Concepts and Proofs from Nicole Oresme: Using the History of Calculus to Teach Mathematics 

      Babb, Jeff (2005)
      This paper examines the mathematical work of the French bishop, Nicole Oresme (c. 1323–1382), and his contributions towards the development of the concept of graphing functions and approaches to investigating infinite ...
    • The metric dimension and metric independence of a graph 

      Currie, James; Oellerman, Ortrud R. (The Charles Babbage Research Centre, 2001)
      A vertex x of a graph G resolves two vertices u and v of G if the distance from x to u does not equal the distance from x to v. A set S of vertices of G is a resolving set for G if every two distinct vertices of G are ...
    • Multi-dimensional sets recognizable in all abstract numeration systems 

      Charlier, Émilie; Lacroix, Anne; Rampersad, Narad (EDP Sciences, 2011)
      We prove that the subsets of Nd that are S-recognizable for all abstract numeration systems S are exactly the 1-recognizable sets. This generalizes a result of Lecomte and Rigo in the one-dimensional setting.
    • The number of order–preserving maps of fences and crowns 

      Currie, James; Visentin, Terry I. (Springer, 1991-06)
      We perform an exact enumeration of the order-preserving maps of fences (zig-zags) and crowns (cycles). From this we derive asymptotic results.
    • On avoidability of formulas with reversal 

      Currie, James D.; Mol, Lucas; Rampersad, Narad (EDP Sciences, 2018-02-13)
      While a characterization of unavoidable formulas (without reversal) is well-known, little is known about the avoidability of formulas with reversal in general. In this article, we characterize the unavoidable formulas ...
    • Opportunity solving: Ordinary people doing extraordinary things, every day 

      Sokal, Laura; Eblie Trudel, Lesley; Babb, Jeff (Canadian Education Network, 2020-10-16)
    • Regular Two-Graphs and Equiangular Lines 

      Gosselin, Shonda (University of WinnipegUniversity of Waterloo, 2004)
      Regular two-graphs are antipodal distance-regular double coverings of the complete graph, and they have many interesting combinatorial properties. We derive a construction for regular two-graphs containing cliques of ...
    • Self-Complementary Hypergraphs 

      Gosselin, Shonda (University of OttawaUniversity of Ottawa and Carleton University (joint program), 2009)
      In this thesis, we survey the current research into self-complementary hypergraphs, and present several new results. We characterize the cycle type of the permutations on n elements with order equal to a power of 2 which ...
    • Shuffling and unshuffling 

      Henshall, Dane; Rampersad, Narad; Shallit, Jeffrey (Bulletin of the European Association for Theoretical Computer Science, 2012)
      We consider various shuffling and unshuffling operations on languages and words, and examine their closure properties. Although the main goal is to provide some good and novel exercises and examples for undergraduate formal ...
    • Skeleton Cave, Leigh Woods, Bristol 

      Mullan, G. J.; Meiklejohn, C.; Babb, J. (University of Bristol Spelaeological Society, 2017)
      An account is given of the discovery and excavation of this small cave in the 1960s. It is recorded that archaeological finds were made, but of these, only a single human mandible can now be traced. Radiocarbon dating shows ...
    • Sliding Down Inclines with Fixed Descent Time: a Converse to Galileo's Law of Chords 

      Babb, Jeff (Canadian Mathematical Society, 2008-12)