Institut for Matematik og Datalogi

Speaker: Yuki Matsubara (University of Southern Denmark)Abstract: A smooth complete intersection X of two quadrics in P^{n+2}  admits an interpretation as a moduli space of bundles.For n = 2, it parametrizes stable rank 2 parabolic bundles on P^1 with five marked points, while for n = 3 it parametrizes stable rank 2 bundles of odd degree with fixed determinant on a genus 2 curve. For general n, it can be interpreted as a moduli space of semistable twisted Spin-bundles. In my talk, I will discuss the topology of the very stable locus X \ W, where W is the wobbly locus, consisting of bundles that admit a nonzero nilpotent Higgs field. The importance of the very stable locus in the geometric Langlands correspondence was emphasized by Laumon. I will explain that W is an irreducible divisor for n >2 and how to compute H_1(X \ W, Z).Using a root stack description, we identify the fundamental group $\pi_1(X \ W)$ with the kernel of a monodromy homomorphism from an orbifold mixed braid group.The Reidemeister—Schreier method then yields an explicit presentation of this fundamental group in every dimension. This talk is based on joint work with S. Bhattacharya (https://arxiv.org/abs/2609.31421).

Speaker: Benjamin Shackleton (​University of Southern Denmark).Abstract: In this pre-PhD work, completed with input from Professor Sir Simon Donaldson and Dr Daniel Platt, I prove the existence of a Ricci flat metric on the Kummer K3 surface. The proof follows the general strategy of Donaldson’s gluing construction. However, we tackle the analysis without appealing to weighted norms or conformal transformations to model spaces, instead relying solely on compact elliptic theory on usual Hölder and Sobolev spaces.The talk will coversetting up the problem and the computation of the estimates used.The paper can be found here: https://arxiv.org/abs/2605.02046.

Speaker: Shing Tak Lam (​University of Warwick).Abstract: In complex geometry, a central theme is the relationship between algebro-geometric stability and the existence of canonical metrics. Examples of this include the Hitchin-Kobayashi correspondence for holomorphic vector bundles, and the Yau-Tian-Donaldson conjecture for varieties. In this talk, I will discuss a parabolic analogue of these results, relating the asymptotics of the associated geometric flows to algebro-geometric filtrations defined by Haiden-Katzarkov-Kontsevich-Pandit and Ibáñez Núñez.

I Danmarks næststørste by flygtede kun et par jøder, da tyskerne startede ’jødeaktionen’ i oktober 1943 – sådan har historikerne hidtil ment.

I Danmarks næststørste by flygtede kun et par jøder, da tyskerne startede ’jødeaktionen’ i oktober 1943 – sådan har historikerne hidtil ment.

Casper Asbjørn Eriksen forsvarer sin ph.d.-afhandling ved et offentligt foredrag: “Computational Methods for Molecular Structures: Biochemical Data Integration and Enumeration”.Professor Kim Skak Larsen vil være ordstyrer ved arrangementet. Ph.d.-forsvaret finder sted i IMADAs Konferencelokale (Ø18-509-2). Alle er velkomne.

Esben Andreas Wrona Bay Sørensen forsvarer sin ph.d.-afhandling ved et offentligt foredrag: “Data Science and Visualization Concerns in Interdisciplinary Research of Changes in the Arctic Ocean”.Lektor Tariq Yousef vil være ordstyrer ved arrangementet. Ph.d.-forsvaret finder sted i U140 (Ø16-501-1). Alle er velkomne.

Studerende udvikler en bred vifte af kompetencer gennem deres uddannelse, men de er ikke altid selv bevidste om alt det, de bliver bedre til undervejs.

Camilla Vang Østergaard forsvarer sin ph.d.-afhandling ved et offentligt foredrag: “Methodological and Practical Considerations of Visual Digital Storytelling for the Heritage of Nazi Persecution”.Lektor Tariq Yousef vil være ordstyrer ved arrangementet. Ph.d.-forsvaret finder sted i U140 (Ø16-501-1). Alle er velkomne.

Speaker: Sebastian Pögel (​University of Zurich).Abstract: TBA

Speaker: Apoorv Tiwari (​University of Southern Denmark).Abstract: Fault-tolerant quantum computation can incur a substantial resource cost when a desired logical operation must be constructed from a restricted set of logical primitives. To make such operations directly available, I will introduce irrep surface codes (ISCs), two-dimensional topological quantum error-correcting codes engineered to transversally implement a prescribed set of logical gates. The target logical gates only need to satisfy two conditions: (i) they generate a finite group, which, up to global phases, is forced by the Eastin-Knill theorem, and (ii) they are irreducible, meaning that any operator commuting with the set of gates must be proportional to the identity. This accommodates arbitrary finite groups of diagonal gates and arbitrary reversible classical gates, since each can be embedded into a larger irreducible finite group of gates. It also enables logical gates outside every finite level of the Clifford hierarchy. To incorporate these operations into surface-code computations, we further develop lattice-surgery protocols to transfer the encoded information between surface codes and ISCs obeying one of two sufficient conditions. Together, these results establish a systematic method for tailoring topological codes to desired logical operations and integrating them into conventional computations.

Rasmus Jensen forsvarer sin ph.d.-afhandling ved et offentligt foredrag: “Geometric Interpolation on the Stiefel and Grassmann Manifolds”.Lektor Benjamin Jäger vil være ordstyrer ved arrangementet. Ph.d.-forsvaret finder sted i U31 (V5-601-1). Alle er velkomne.

Speaker: Arim Song (​Friedrich-Alexander University Erlagen-Nürnberg).Abstract: $W$-algebras are families of vertex algebras associated with Lie algebras and their nilpotent elements. They can be viewed as chiral analogues of the Feigin-Frenkel center of the Lie algebra and exhibit rich structures, including Feigin–Frenkel duality and coset realizations. The $W_\infty$-algebra is a two-parameter family of vertex algebras whose quotients recover type A principal $W$-algebras. It provides a powerful framework for classifying vertex algebras with prescribed strong generating type and has led to the discovery of isomorphisms among various families of vertex algebras, including results that partially establish the celebrated triality conjecture of Gaiotto and Rapčák. The construction of $W$-algebras extends naturally to Lie superalgebras, giving rise to $W$-superalgebras. However, many questions concerning dualities among these algebras remain open. In recent joint work with Creutzig, Kovalchuk, Linshaw, and Suh, we extended the $W_\infty$-algebra framework to type A Lie superalgebras and established dualities for type A principal $W$-superalgebras. In this talk, I will introduce $W$-algebras and $W_\infty$-algebras, and discuss their structural properties. If time permits, I will briefly discuss the recent developments in the super setting.