The next meeting of the Joint Seminar of Analysis, Geometry and Topology Department will be held on April 4, 2023 at 2:00 pm (UTC+3)  in Room 478 of IMI. A talk on: Introduction to spectral graph theory  will be delivered by Peter Petrov, Institute of Mathematics and Informatics, Bulgarian Academy of Sciences. Everybody is invited. Abstract. This is the first lecture of a series of 2-3 lectures on algebraic graph theory. A very basic knowledge in linear algebra should be enough as a prerequisite, so that the talk could be understood by people from informatics or biology, also by students. Simple examples will accompany any notion. All knowledge needed from graph theory will be given. The Laplacian of a simple graph will be defined, showing [...]

The next meeting of the Joint Seminar of Analysis, Geometry and Topology Department will be held on November 15, 2022 at 11:00 am (UTC+3)  in Room 478 of IMI. A talk on: Zener model with General fractional calculus: Thermodynamical Restrictions  will be delivered by Teodor M. Atanackovic and Stevan Pilipovic, Serbian Academy of Sciences and Arts and University of Novi Sad, Serbia. Everybody is invited. Abstract. We study a Zener type model of viscoelastic body within the context of general fractional calculus and derive restrictions on coefficients that follow from the dissipation inequality that is, the entropy inequality under isothermal conditions. We show, for a stress relaxation and a wave propagation, that the restrictions that follow from the entropy inequality are sufficient to guarantee the existence [...]

The next meeting of the Joint Seminar of Analysis, Geometry and Topology Department will be held on November 8, 2022 at 1:30 pm (UTC+3)  in Room 478 of IMI. A talk on: Surfaces Associated with Pascal and Catalan Triangles  will be delivered by Leonard DAUS1, Marilena JIANU1 and Adela MIHAI1,2 1 Technical University of Civil Engineering Bucharest, Romania 2 Transilvania University of Brasov, Romania. Everybody is invited. Abstract. An open problem in reliability theory is that of finding all the coefficients of the reliability polynomial associated with particular networks. Because reliability polynomials can be expressed in Bernstein form (hence linked to binomial coefficients), it is clear that an extension of the classical discrete Pascal’s triangle (comprising all the binomial coefficients) to a continuous version [...]

The next meeting of the Joint Seminar of Analysis, Geometry and Topology Department will be held on April 28, 2022 at 1:00 pm (UTC+3)  in Room 478 of IMI. A talk on: Isotropic Killing vector fields and structures on complex surfaces  will be delivered by Gueo Grantcharov, Florida International University, USA. Everybody is invited. Abstract. In a 4-dimensional vector space with scalar product of signature (2,2), two independent vectors spanning a maximal isotropic (null) plane determine a canonical action of the para-quaternioins. We noticed that on an oriented 4-manifold with such pseudo-Riemannian metric, existence of two isotropic (null) Killing vector fields leads to integrability of the induced structure - called para-hypercomplex, and the metric is anti-selfdual. Using the Kodaira classification one can describe the [...]

The next meeting of the Joint Seminar of Analysis, Geometry and Topology Department will be held on March 29, 2022, at 1:30 pm (UTC+2) in Room 478 of IMI-BAS.. A talk on: On Squeezing Function for Planar Domains will be delivered by Ahmed Yekta Ökten, Institut de Mathématiques de Toulouse, France. Everybody is invited. Abstract. Let Ω be a domain in ℂ𝑛 such that the set 𝐸(Ω, 𝐵𝑛) of injective holomorphic maps from Ω into the unit ball 𝐵𝑛 ⊂ ℂ𝑛 is non-empty. The squeezing function of Ω, denoted by 𝑆Ω is defined as 𝑆Ω(𝑧) = sup{𝑟 ∈ (0, 1): 𝑟𝐵𝑛 ⊂ 𝑓(Ω),      𝑓 ∈ 𝐸(Ω, 𝐵𝑛),      𝑓 (𝑧) = 0}. It follows from the definition that the squeezing function is biholomorphically [...]

The next meeting of the Joint Seminar of Analysis, Geometry and Topology Department will be held on February 15, 2022, at 1:00 pm (UTC+2) via Zoom. A talk on: Kähler Manifolds of Quasi-constant Holomorphic Sectional Curvature and Generalized Sasakian Space Forms will be delivered by Cornelia-Livia Bejan,  “Gheorghe Asachi” Technical University of Iasi, Romania. Everybody is invited. Abstract. Two geometric notions, namely Kähler manifolds of quasi-constant holomorphic sectional curvature and generalized Sasakian space forms, are related to each other, for the first time. Some conditions under which each of these structures induces the other one, are provided here. Several results are obtained on direct products (which are special cases of Naveira’s classification), warped products or hypersurfaces of manifolds and relevant examples are included. A result [...]

The next meeting of the Joint Seminar of Analysis, Geometry and Topology Department will be held on  December 14, 2021 at 1:00 p.m. (GMT+2:00) via Zoom. A talk on: Towards Homological Mirror Symmetry for weighted projective planes over the complex numbers will be delivered by: Marin Genov. Everybody is invited. Join Zoom link: https://miami.zoom.us/j/93060507383?pwd=Y2MremVpcmJrdkRiN3N3QVVZZC9HQT09 Meeting ID: 930 6050 7383 Passcode: 825839  

The next meeting of the Joint Seminar of Analysis, Geometry and Topology Department will be held online on  October 19, 2021 at 2:00 p.m. (GMT+3:00). A talk on: Index counting theories and  linear stability of  periodic waves will be delivered by: Sevdzhan Hakkaev, Shumen University. Everybody is invited. Abstract. In this talk, we will present some results on the stability of periodic waves. In the models that we will consider, stability problem leads to the study of the spectral problems of the form and computations of the quantities involved in the stability index. Contact : V. Milousheva, vmil@math.bas.bg Join Zoom link: https://us02web.zoom.us/j/83064361660?pwd=T2tJVmswdFgzWmdUYkdWQWtUM3owQT09 Meeting ID: 830 6436 1660 Passcode: 453424  

The next meeting of the Joint Seminar of Analysis, Geometry and Topology Department will be held on June 22, 2021, from 11:30 via Zoom. A talk on: General Rotational Surfaces in Pseudo-Euclidean 4-Spaces will be delivered by: Victoria Bencheva. Everybody is invited. Abstract. Rotational surfaces are rich source of examples both in Euclidean and pseudo-Euclidean spaces. We consider the so-called general rotational surfaces of elliptic and hyperbolic type in the Minkowski 4-space and the pseudo-Euclidean 4-space with neutral metric which are analogous to the general rotational surfaces introduced by C. Moore in the Euclidean space R^4. We describe analytically some basic subclasses of general rotational surfaces, namely: minimal, flat, with flat normal connection, with parallel normalized mean curvature vector field. Topic: Общ семинар на [...]