Date/Time : 20 Aug 2026 16:00
Venue : S17 #04-04 (Seminar Room 3)
Speaker : Yongnam Lee, Institute for Basic Science

Motivated by DeVleming’s work on moduli of surfaces in P^3 and Chen-Hu-Jiang’s work on moduli of threefolds with volume 2 and geometric genus 4, we study the deformation of pairs of P^3 and hypersurfaces using the classification of Q-Gorenstein degenerations of P^3 with canonical singularities. We prove that if a degenerating threefold has canonical singularities, then the moduli space is smooth at the corresponding pair. Consequently, we find some boundary divisors of the moduli of smooth hypersurfaces. Finally, using the double cover method, we derive some information on the moduli space of threefolds X with canonical singularities with the same volume and geometric genus as a double cover of P^3 branched over a hypersurface. This is joint work with Jungkai Chen and Phin-Sing Soo.

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Date/Time : 19 Aug 2026 13:30
Venue : S16 #05-18
Speaker : Liron Speyer, Okinawa Institute of Science and Technology

I will give a brief account of the combinatorial representation theory of type A Iwahori–Hecke algebras, and their realisation as cyclotomic KLR algebras. In this story, I will largely focus on the decomposition number problem as one of the key problems in this field, and James’s conjecture, which drove a lot of research until Williamson showed it to be false in 2013. While Williamson’s counterexample is incredibly large, and beyond explicit computation, I recently discovered a new counterexample, which is of minimal size. I will explain this counterexample in the talk, as well as touching on how I found it.

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Date/Time : 13 Aug 2026 16:00
Venue : S17 #04-06 (Seminar Room 1)
Speaker : Boaz Klartag, Tel Aviv University and Weizmann Institute of Science

We survey progress from the past five years on the distribution of mass in high-dimensional convex bodies and in probability distributions with convexity properties. The concentration of measure phenomenon has traditionally been studied in highly regular or structured settings, such as spheres, Hamming cubes, Gaussian measures, Markov chains, and martingales. It turns out that convexity assumptions provide an alternative source of regularity in high dimensions with remarkably similar features: Lipschitz functions are highly concentrated, the isoperimetric problem is nearly saturated by half-spaces (up to logarithmic factors), and the central limit theorem is nearly as strong as in the setting of independent random variables. The main developments discussed include the resolution of Bourgain’s slicing problem and the Variance Conjecture, as well as recent progress on the isoperimetric problem for high-dimensional convex bodies. Based on joint work with P. Bizeul and J. Lehec.

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Date/Time : 12 Aug 2026 16:00
Venue : S17 #04-05 (Seminar Room 2)
Speaker : Wenfei Liu, Xiamen University

The set V of volumes of stable surfaces, as a subset of positive rational numbers, satisfies the descending chain condition. Equivalently, any nonempty subset of V attains the minimum.

In this talk, I will report a joint work with Jihao Liu, showing that the minimal volume of a stable surface with Picard rank 1 is 1/6351, uniquely realized by a normal rational stable surface previously constructed from P^2 with 4 lines by Valery Alexeev and Wenfei Liu.

In the proof of the minimum, we use various filters to narrow down the possible basket of singularities on such a surface.

The last and very crucial one, the so-called pluricanonical product-dimension filter, was suggested to us by the AI!

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Date/Time : 12 Aug 2026 15:00
Venue : S17 #04-06 (Seminar Room 1)
Speaker : Boaz Klartag, Tel Aviv University and Weizmann Institute of Science

We prove there exists a lattice sphere packing in R^n whose density is at least c n^2 / 2^n, where c > 0 is a universal constant. Previously known constructions of sphere packings in R^n had densities of the order of magnitude of n / 2^n, up to logarithmic factors. Our proof utilizes a stochastically evolving ellipsoid that accumulates at least c n^2 lattice points on its boundary, while containing no lattice points in its interior except for the origin.

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Date/Time : 12 Aug 2026 13:30
Venue : S16 #05-18
Speaker : Dinesh S. Thakur, University of Rochester

After reviewing some basic facts of classical diophantine approximation, diophantine equations, we will discuss various analogs, contrasts, tools, and open questions in the finite characteristic situation.

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Date/Time : 12 Aug 2026 17:00
Venue : S17 #04-04 (Seminar Room 3)
Speaker : Wang Wei, Sun Yat-Sen University

A (binary) tree is positive iff its infinite paths form a set with positive Lebesgue measure. It is a well-known phenomenon in algorithmic randomness that positive trees contain infinite paths with weak computational power. By Cantor, positive trees always have perfect subtrees and even positive perfect subtrees. Chong et al. [1] studied computational power of perfect subtrees of positive trees, and to some extend showed that positive trees also contain perfect subtrees of weak computational power. This work was followed up by Barmpalias and Wang [2], by Barmpalias and Zhang [3], and also by Greenberg, J. Miller and Nies [4]. This talk will survey the main results in the above works, and also sketch a recent result that every ∆n positive tree contains a lown perfect subtree.

[1] Chong, Chitat and Li, Wei and Wang, Wei and Yang, Yue, On the com-putability of perfect subsets of sets with positive measure, Proceedings of the Amer-ican Mathematical Society, vol. 147 (2019), no. 9, pp. 4021–4028.
[2] Barmpalias, George and Wang, Wei, Pathwise-randomness and models of second-order arithmetic, Information and Computation, vol. 299 (2024), 105181.
[3] Barmpalias, George and Zhang, Xiaoyan, Growth and irreducibility in path-incompressible trees, Information and Computation, vol. 297 (2024), 105136.
[4] Greenberg, Noam and Miller, Joseph S. and Nies, André, Highness prop-erties close to PA completeness, Israel Journal of Mathematics, vol. 244 (2021), pp. 419–465.

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Date/Time : 07 Aug 2026 9:30 am to 12:00 pm
Venue : S17 #04-04 (Seminar Room 3)
Speaker : Various speakers,

The workshop will focus on concrete Mathematics teaching cases, especially AI-supported and blended-learning approaches. It will be discussion-led: we will use case studies and focused group discussions to explore particular teaching topics in a practical and efficient way. We warmly welcome colleagues to participate actively in the discussions.

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Date/Time : 07 Aug 2026 15:00
Venue : S17 #05-11 (Seminar Room 5)
Speaker : Zijian Wang, Nankai University and NUS

In this talk, we will present several new results investigating the (in)stability properties of rotating drops and jets. 

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