Pure Mathematics Research: Recent submissions

Now showing items 11-14 of 14

    • Growth rates for subclasses of Av(321) 

      Albert, M.H.; Atkinson, M.D.; Brignall, R; Ruskuc, Nik; Smith, R; West, J (2010-10-22) - Journal article
      Pattern classes which avoid 321 and other patterns are shown to have the same growth rates as similar (but strictly larger) classes obtained by adding articulation points to any or all of the other patterns. The method of ...

    • Generators and relations for subsemigroups via boundaries in Cayley graphs 

      Gray, R; Ruskuc, Nik (2011-11) - Journal article
      Given a finitely generated semigroup S and subsemigroup T of S we define the notion of the boundary of T in S which, intuitively, describes the position of T inside the left and right Cayley graphs of S. We prove that if ...

    • Presentations of inverse semigroups, their kernels and extensions 

      Carvalho, C.A.; Gray, R; Ruskuc, Nik (2011-06-01) - Journal article
      Let S be an inverse semigroup and let π:S→T be a surjective homomorphism with kernel K. We show how to obtain a presentation for K from a presentation for S, and vice versa. We then investigate the relationship between the ...

    • Simple extensions of combinatorial structures 

      Brignall, R; Ruskuc, Nik; Vatter, V (2011-07) - Journal article
      An interval in a combinatorial structure R is a set I of points which are related to every point in R \ I in the same way. A structure is simple if it has no proper intervals. Every combinatorial structure can be expressed ...