Logic Seminar in AY 2026/2027 at NUS

• Wednesday 12/08/2026, 17:00 hrs, Week 1, Department of Mathematics, Room S17#04-04.
  Wang Wei. Iterated jumps of perfect subtrees of positive trees.
  Talk announcement.
  
  
• Wednesday 19/08/2026, 17:00 hrs, Week 2, Department of Mathematics, Room S17#04-04.
  Clement Yung. Weak A2 spaces, the Kastanas game and strategically Ramsey sets.
  In the past century, the insight behind the original Ramsey's theorem proved to be applicable to a wide range of mathematics, such as number theory, functional analysis and topology. This spurred two particular directions of Ramsey theory: The first one is known as topological Ramsey theory, a general procedure developed by Carlson and Simpson to prove many seemingly unrelated Ramsey's theorem-like results. The second one is the Ramsey theory of Banach spaces, kickstarted by Gowers' unexpected application of Ramsey theory to resolve a long-standing open problem in Banach space theory. In this talk, I introduce the theory of weak A2 spaces, which serves as a possible intersection between these two Ramsey theories and discuss how several infinite games that appeared in these Ramsey theories (the Kastanas game, the Gowers game and the asymptotic game) are closely related.
  
  
• Wednesday 26/08/2026, 17:00 hrs, Week 3, Department of Mathematics, Room S17#04-04.
  Rod Downey. The geometry of computable Banach spaces.
  A computable Banach space X = (X, || · ||, +, ·) is a Banach space with a computable dense sequence of points which makes X a computable metric space using the norm, for which the operations are computable functions. Most, but not all, familiar spaces of analysis and physics commonly met are such spaces. In the same way as classical vector space theory revolves around (Hamel) bases, Banach spaces are best understood using what is called a Schauder basis. There are many, many questions around this concept, both classically and in the effective content.
  In this talk I will overview many of the questions and results we have so far, and particularly report on some recent work seeking to understand the effective content of Kadets’ Theorem, which states (more or less) that all infinite dimensional Banach spaces look the same if we forget the norm: any two infinite-dimensional, separable Banach spaces are homeomorphic as topological spaces. Surprisingly, this result can be proven for computable Banach spaces using only the halting problem, which seems rare in effective topology.
  
  
• Wednesday 02/09/2026, 16:00 hrs Week 4, Department of Mathematics, Room S17#04-05.
  Eric Walsberg, Trace definability and model-theoretic linearity.
  I will introduce trace definability between first order structures / theories and explain how it can be used to give dichotomies between linearity and field structure in certain settings.
  
  
• Wednesday 02/09/2026, 17:00 hrs Week 4 Department of Mathematics, Room S17#04-04.
  Roy Shalev. The small Dowker space problem.
  It is well-known that the product of two normal topological spaces need not be normal, but what about the normality of the product of a normal space X with the unit interval [0, 1]? A counterexample space X is called a "Dowker space". In 1971, Rudin proved that such a space exists, but it remains open whether there must exist a Dowker space of size ℵ₁. In this talk, I shall report on a joint work with Rinot and Todorčević in which we present a weak sufficient condition for the existence of a small Dowker space.
  
  
• Wednesday 09/09/2026, 17:00 hrs, Week 5, Department of Mathematics, Room S17#04-04.
  
  
  
• Wednesday 16/09/2026, 17.00 hrs, Week 6, Department of Mathematics, Room S17#04-04.
  
  
  
• Wednesday 30/09/2026, 17:00 hrs, Week 7, Department of Mathematics, Room S17#04-04.
  
  
  
• Wednesday 07/10/2026, 17:00 hrs, Week 8, Department of Mathematics, Room S17#04-04.
  
  
  
• Wednesday 14/10/2026, 17:00 hrs, Week 9, Department of Mathematics, Room S17#04-04.
  
  
  
• Wednesday 21/10/2026, 17:00 hrs, Week 10, Department of Mathematics, Room S17#04-04.
  
  
  
• Wednesday 28/10/2026, 17.00 hrs, Week 11, Department of Mathematics, Room S17#04-04.
  
  
  
• Wednesday 04/11/2026, 17:00 hrs, Week 12, Department of Mathematics, Room S17#04-04.
  
  
  
• Wednesday 11/11/2026, 17:00 hrs, Week 13, Department of Mathematics, Room S17#04-04.