Seminar Talks Schedule


Wednesday 22 November 2017, 16.00-17.00 in MA119
Speaker: Kieran Fleming (University of Leicester)
A diagonal approximation for the associahedra
The sequence of associahedra, or Stasheff polytopes, are a series of convex polytopes that effectively model the structure of A-infinity algebras. Constructing a diagonal approximation on the associahedra is therefore equivalent to applying an A-infinity structure to a product of A-infinity algebras. There have been a variety of solutions provided in terms of some deformation of a cubical or simplicial decomposition of the associahedra. For this talk I will construct the diagonal approximation using a simplicial decomposition, show there is an alternative combinatorial formula that can be used to construct it directly, and highlight the obstruction to co-associativity that arises when the construction is iterated. If time allows I will also give some examples of where this material is of use in my current research.

Wednesday 1 March 2017, 14:00-16:00 BEN LT4

Speaker: Scott Balchin (University of Leicester)

Title: Model Categories and Simplicial Presheaves

Abstract: In this talk we will be interested in a certain Quillen model structure on the category of simplicial presheaves over a site.  Such a construction will allow us to define what we mean by ∞-topoi, cohomology theories and derived stacks. In the first half we will introduce the theory of closed Quillen model categories along with some motivating examples and constructions.  In short, a model category is one where we mark special classes of maps which allow us to do homotopy theory in our category. In the second half we will construct a particular model structure on the category of simplicial presheaves on a categorical site (contravariant functors to sSet).  We then discuss some interesting choices of sites and their resulting algebraic and topological theory. If time allows I will make a brief comment on how this theory ties into my PhD research on equivariant homotopical stacks.

Thursday 8 December 2016, 16:00-18:00 MA119

Speaker: Andrew Smith (University of Leicester)

Title: An Introduction to Higher Category Theory.

Abstract   References

Wednesday 5 October at 4 pm in Ben LT10.

Speaker: Matej Dostal (Czech Technical University Prague)

Title: Categorical compositional semantics of natural language with many-valued meaning.

Abstract: We formalise the generalised quantifier theory of natural language (due to Barwise and Cooper) in the setting of compact closed categories with bialgebras. For the case of the category Rel this gives precisely Barwise and Cooper semantics, but it allows us to study many-valued semantics of ``fuzzy'' sentences by computing the meaning of senteces in the category V-Rel of many-valued relations.

  • Alexander Kurz   “Nominal Sets” Friday 22 July 2016 14:00-16:00 , Room G4 Computer Science Building. Reference:  Andrew M. Pitts. An Equivalent Presentation of the  Bez- Coquand-Huber Category of Cubical Sets.


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