Institute of Mathematics and Informatics

Семинар на МЦМН и съвместно заседание със семинара АГТ
2025-12-02 13:00 - 16:00 (Europe/Sofia) | Институт по математика и информатика – БАН, Block 8, 1113 БАН IV км., София, Bulgaria
Следващото заседание на семинара на МЦМН ще се състои във вторник, 2 декември 2025 г. Доклади ще изнесат Рой Маген от МЦМН и Ливиу Орнеа от Букурещския университет, като вторият доклад е в рамките на съвместно заседание със семинара на секция “Анализ, Геометрия и Топология”. Програмата е следната.

ICMS Seminar and AGT Seminar

Tuesday, December 2nd, room 403 IMI-BAS.

13:00 — Roy Magen (ICMS, IMI-BAS)

Flavours of homotopy theory

14:00 — Liviu Ornea (University of Bucarest)

Distinguished non-Kähler metrics on compact complex manifolds

Abstract (Magen):
In this talk we will consider different flavours of homotopy theory for different types of geometric contexts. First we will recall the usual definitions of the homotopy category, and equivariant homotopy categories, and we will show how we can think of these in terms of (equivariant) smooth manifolds. This will give us a suitable framework with which to adapt the notion of homotopy theory to different geometries.
We first use this framework to give a brief overview of the story in algebraic geometry, which produces motivic homotopy theory. Next, we will use our framework to discuss notions of homotopy theories parametrized by a geometric object, and discuss some consequences.
Depending on time constraints and interest, we will end either by discussing work relating this homotopical framework to 6-functor formalisms, by going over a version of this story in the complex analytic setting, or by introducing C∞-schemes and discussing possibilities for an extension of the story for manifolds to this setting.
Abstract (Ornea):

I shall review the definitions of LCK, pluriclosed and balanced metrics and discuss their incompatibility on the same compact complex manifold.

Съвместно заседание на семинара на МЦМН и семинара на секция МОИ
2025-11-26 16:00 - 17:30
26 ноември 2025 г., сряда, от 16:00 ч. в Зала 403 на ИМИ – БАН.
Съвместно заседание на Семинара на МЦМН и Семинара на секция Математически основи на информатиката
Frank Vallentin (Universität zu Köln)
Least distortion Euclidean embeddings of flat tori
Резюме: In the emerging field of bi-Lipschitz invariant theory, one studies embeddings of orbit spaces H/G (H a Hilbert space, G a subgroup of its automorphisms) into simpler Hilbert spaces via distance-preserving maps up to a constant factor.

In this talk, I present an infinite-dimensional semidefinite program that computes least-distortion embeddings of flat tori Rn/L, where L is an n-dimensional lattice, into Hilbert spaces. Using symmetry reduction techniques, this infinite-dimensional semidefinite program reduces to an infinite-dimensional linear program.
Even with this simplification, solving the program remains challenging. By combining this approach with the linear programming bound for spherical designs, combined with brute-force methods, we finally are able to determine the least-distortion embeddings of Rn/Zn, R2/A2, and R8/E8.
(Based on joint work with Arne Heimendahl, Moritz Lücke, Philippe Moustrou, and Marc Christian Zimmermann)

Least distortion Euclidean embeddings of flat tori, ICMS seminar talk by Frank Vallentin

Семинар на МЦМН
2025-11-25 13:00 - 14:30
Вторник, 25 ноември 2025 г., 13:00, room 403, IMI-BAS.

Deepanshu Prasad (МЦМН, ИМИ – БАН)
An Extension of Sato-Kimura Theorem for Semi-invariant rings

Резюме: We give an analog of a result of Sato-Kimura in the context of a semi-invariant ring for a finite dimensional algebra over an algebraically closed field K of characteristics 0. Then, we examine the case of finite dimensional hereditary algebras over K. This is joint work with Charles Paquette and David Wehlau.

An Extension of Sato-Kimura Theorem for Semi-invariant rings, ICMS seminar talk by Deepanshu Prasad

Съвместно заседание на Семинара по особености и Семинара на МЦМН
2025-11-18 13:00 - 15:30
Joint meeting of the Seminar on Singularities and the ICMS Seminar, with a lecture by Pablo Cuadrado. The program is as follows.

Tuesday, November 18, room 403, IMI-BAS.

13:00 — Giovane Galindo (ICMS, IMI-BAS)
Bundle-type sub-Riemannian structures on holonomy bundles

14:00 — Pablo Portilla Cuadrado (Universidad Politécnica de Madrid)
The medial axis of the Milnor fiber

Abstract (Galindo): In this talk we present the notion of Gromov-Hausdorff distance, a novel field of study that aims to understand the topology of the moduli space of Riemannian metrics on a given manifold. We will then present new results on the subject concerning the collapse of principal bundles onto reductive homogeneous spaces.

Abstract (Cuadrado): Let f(x,y) define an isolated singularity at the origin. In this talk we explore a new flat metric induced on the Milnor fiber of f by the associated complex Hamiltonian vector field. With the help of this metric we can define a spine on each Milnor fiber via the classical method of the medial axis. This spine depends on the choice of boundary for the Milnor fiber. It is subanalytic and comes equipped with a retraction from the boundary onto it. We hope to understand the geometry of the versal unfolding space via these spines. This ongoing joint work with Norbert A’Campo.

Семинар на МЦМН
2025-11-04 13:00 - 14:30
Семинар на МЦМН
Вторник, 4.11.2025, 13:00 ч., Зала 403, ИМИ – БАН
Лектор: Leonardo Cavenaghi (МЦМН, ИМИ – БАН)
Тема на доклада: Exotic phenomena in topology and geometry

Резюме: This talk, aimed at a general audience of mathematicians, discusses very geometric models of exotic spheres.
Exotic spheres are manifolds homeomorphic to classical spheres but not diffeomorphic to them. We will outline some constructions via group actions and discuss their admissible geometries. For instance, until this day, it is not known whether an exotic sphere admits a metric of positive sectional curvature, but some do not even admit positive scalar curvature.
In this talk, we also outline how one can indirectly study their geometries, aiming to gain a better understanding of their admissible geometries, for example, regarding the existence of Lorentzian metrics and the spectral problem.

Семинар на МЦМН
2025-06-20 15:30 - 18:00
Следващото заседание на семинара на МЦМН ще се състои в петък, с доклади на Алексанър Стоколос и Ернесто Луперсио.
ICMS Seminar
Friday, June 20-th. Room 403 IMI-BAS.
15:30 – 16:30. Alexander Stokolos (Georgia Southern University)
On extremal polynomials
Abstract: I will present known and new polynomials emerging from the extremal problems of geometric complex analysis.
16:45 – 17:45. Ernesto Lupercio (IMI-BAS and Cinvestav IPN México)
Analysis in Loop Spaces and Genera
Abstract: Analysis on loop spaces, motivated by ideas from conformal field theory, leads naturally to the construction of elliptic genera—topological invariants with deep modular and representation-theoretic properties.
Мore information can be found at the seminar’s website
https://icms.bg/category/icms-seminar/

Семинар на МЦМН
2025-06-13 14:00 - 17:00
Семинарът на МЦМН продължава със серия от четири лекции на д-р Петър Далаков, както следва:
Дата: 13-ти юни
Място: стая 403, ИМИ-БАН
14:00 – 15:30. Peter Dalakov
Special Kaehler geometry and some applications (Part IV)
16:00 – 17:00. Ernesto Lupercio
Elliptic genera and the geometry of loop spaces and applications
Резюмета и допълнителна информация можете да намерите на страницата на семинара:
https://icms.bg/category/icms-seminar/

Семинар на МЦМН
2025-06-10 14:00 - 15:30, 2025-06-06 14:00 - 15:30, 2025-06-03 14:00 - 15:30
Семинарът на МЦМН продължава със серия от четири лекции на д-р Петър Далаков, както следва:
Дати: 3, 6, 10, 13-ти юни, 14:00 часа
Място: стая 403, ИМИ-БАН
Лектор: Петър Далаков (ИМИ и АУБГ)
Тема: Special Kaehler Geometry and some applications
Резюме: In this short sequence of lectures we will discuss the notion of special Kaehler structure and some of its links to complex algebraic geometry, in particular, complex Lagrangians, variations of Hodge structures and algebraic integrable systems. The sequence will conclude with examples related to various moduli spaces of Higgs bundles on curves.
Повече информация можете да намерите на страницата на семинара:
https://icms.bg/category/icms-seminar/

Семинар на МЦМН
2025-06-06 14:00 - 17:00
The ICMS Seminar will meet this Friday, June 6-th, at 14:00, with three lectures by
Peter Dalakov, Lyudmil Katzarkov and Ernesto Lupercio from IMI-BAS.
The schedule is the following.
June 6-th. Room 403 IMI-BAS.
14:00 – 14:50. Peter Dalakov
Special Kaehler Geometry and some applications (Part II)
15:00 – 15:50. Lyudmil Katzarkov
Atoms and Minimal Model Program
16:00 – 16:50. Ernesto Lupercio
Elliptic genus and applications
Abstracts and more information can be found at
https://icms.bg/category/icms-seminar/
