• CARMA COLLOQUIUM
  • Speaker: Dr Michal Ferov, CARMA, The University of Newcastle
  • Title: Groups, machines, algae and trees
  • Location: Room V205, Mathematics Building (Callaghan Campus) The University of Newcastle
  • Time and Date: 4:00 pm, Tue, 4th Apr 2017
  • Abstract:

    In a way, mathematics can be seen as a language game, where we use symbols, together with some rewriting rules, to represent objects we are interested in and then ask what can be said about the sequences of symbols (languages) that capture certain phenomena. For example, given a group G with generators a and b, can we recognise (using a computer) the sequences of generators that correspond to non-trivial elements of G? If yes, how strong computer do we need, i.e. how complicated is the language we are studying?

    There is a natural duality between various types of computational models and classes of languages that can be recognised by them. Until recently most problems/languages in group theory were classified within the Chomsky hierarchy, but there are more computational models to consider. In the talk I will briefly introduce L-systems, a family of classes of languages originally developed to model growth of algae, and show that the co-word problem in Grigorchuk's group, a group of particularly nice transformations of infinite binary tree, can be seen as a language corresponding to a fairly simple L-system.

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  • CARMA GROUP THEORY RHD MEETING
  • Speaker: Dr Michal Ferov, CARMA, The University of Newcastle
  • Title: Galois theory
  • Location: Room V206, Mathematics Building (Callaghan Campus) The University of Newcastle
  • Time and Date: 11:00 am, Thu, 23rd Feb 2017
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  • CARMA GROUP THEORY RHD MEETING
  • Speaker: Dr Michal Ferov, CARMA, The University of Newcastle
  • Title: Galois theory for infinite algebraic extensions
  • Location: Room V205, Mathematics Building (Callaghan Campus) The University of Newcastle
  • Time and Date: 11:00 am, Fri, 17th Feb 2017
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  • CARMA GROUP THEORY RHD MEETING
  • Speaker: Dr Michal Ferov, CARMA, The University of Newcastle
  • Title: Separating cyclic subgroups in graph products
  • Location: Room V205, Mathematics Building (Callaghan Campus) The University of Newcastle
  • Time and Date: 11:00 am, Thu, 17th Nov 2016
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  • CSSE SEMINAR
  • Speaker: Dr Michal Ferov, CARMA, The University of Newcastle
  • Title: Enhancing LambdaMART Using Oblivious Trees
  • Location: Room EF122, Engineering Building EF (Callaghan Campus) The University of Newcastle
  • Time and Date: 2:00 pm, Fri, 28th Oct 2016
  • Note change of date.
  • Abstract:

    Learning to rank is a machine learning technique broadly used in many areas such as document retrieval, collaborative filtering or question answering. We present experimental results which suggest that the performance of the current state-of-the-art learning to rank algorithm LambdaMART, when used for document retrieval for search engines, can be improved if standard regression trees are replaced by oblivious trees. This paper provides a comparison of both variants and our results demonstrate that the use of oblivious trees can improve the performance by more than 2:2%. Additional experimental analysis of the inuence of a number of features and of a size of the training set is also provided and confirms the desirability of properties of oblivious decision trees.

    About the Speaker: Dr Michal Ferov is a Postdoctoral Research Fellow in the School of Mathematical and Physical Sciences,Faculty of Science and Information Technology.

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  • CARMA GROUP THEORY RHD MEETING
  • Speaker: Dr Michal Ferov, CARMA, The University of Newcastle
  • Title: Separability properties and graph products of groups
  • Location: Room V205, Mathematics Building (Callaghan Campus) The University of Newcastle
  • Time and Date: 11:00 am, Thu, 20th Oct 2016
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