У оквиру семинара Групе за гравитацију, честице и поља, у петак, 17. октобра 2025. године у 13:15 у сали 360 Института за физику у Београду, Иван Шупић (Универзитет у Греноблу, Сен Мартен д’Ер, Оверња-Рона-Алпи) одржаће предавање:

Compiled Bell inequalities 

САЖЕТАК:

Bell inequalities quantitatively separate classical from quantum correlations, serving as a cornerstone for experimental tests of entanglement and for device-independent approaches. The compilation of Bell tests enables such scenarios to be implemented without the requirement of physical spatial separation: instead of isolated laboratories, cryptographic protocols are used to constrain and coordinate the behavior of the participants. A key question is to understand the asymptotic quantum values of these compiled tests that is, the limiting correlations achievable when the players have unbounded local dimension and perform sequential measurements. Technically, I will present an operator-algebraic framework connecting sequential measurements with commuting-operator models. This includes the construction of universal C*-algebras generated by sequential PVM/POVM families, the characterization of asymptotic correlations through their representations, and the development of key technical tools (such as a chain rule for
Radon–Nikodym derivatives of completely positive maps) that facilitate comparison between different strategies. Finally, I will outline our main results and open problems arising from the connection between cryptographic compilation of Bell tests, the limits of quantum correlations, and the structure of C*-algebras of sequential measurements.

У оквиру семинара Групе за гравитацију, честице и поља у петак, 17. октобра 2025. године у 11:15 у сали 360 Института за физику у Београду, Ђорђе Богдановић (Физички факултет, Универзитет у Београду) одржаће предавање:

Noncommutative Scalar Quantum Field Theory

САЖЕТАК:

We study a scalar field theory with cubic interaction, quantized using the homological quantization approach within an algebraic framework. Noncommutativity is introduced in two distinct ways, and the resulting theories are compared. In the first case, the underlying L-infinity algebra of the field theory remains undeformed (commutative), while the interaction is defined via the standard star product, yielding results equivalent to those obtained through the path integral approach. In the second case, both the interaction and the underlying L-infinity algebra are twist-deformed, giving rise to a different noncommutative field theory known as braided field theory.

У оквиру семинара Центра за физику чврстог стања и нове материјале Института за физику у Београду, у понедељак, 20. октобра 2025. године у 12 часова у читаоници библиотеке „Др Драган Поповић“, др Срђан Ставрић (Институт за нуклеарне науке „Винча“) одржаће предавање:

Why all that fuss about altermagnets?

САЖЕТАК:

Altermagnets are an emerging class of magnetic materials characterized by a collinear compensated arrangement of magnetic moments and a momentum-dependent spin splitting in the band structure. This peculiar combination, arising from specific crystal symmetries [1], merges the most desirable traits of antiferromagnets – such as ultrafast dynamics without stray fields – with the strong time-reversal-symmetry-breaking responses characteristic for ferromagnets [2]. Found in a diverse range of materials from metals to insulators, altermagnets offer a versatile new platform for next-generation spintronics, paving the way for high-density magnetic memory and terahertz nano-oscillators [3]. This talk will explore the fundamental principles and significant potential of this exciting new class of materials. We will begin by establishing a new taxonomy of collinear magnets, introducing the distinct realms of ferromagnets, antiferromagnets, and altermagnets, and extending the concept to non-collinear p-wave magnets. A special focus will be on recent observation of p-wave magnetism in a spin-spiral type-II multiferroic NiI₂ [4]. We will explore how the symmetry-protected coupling between chirality and polar order enables electrical control of a primarily non-relativistic spin polarization in this material. Finally, we will examine the role of spin-orbit coupling in altermagnets and show what implications it may have on electronic and magnetic properties. In particular, we will focus on two-dimensional altermagnets, where this relativistic interaction cannot be neglected as it is the source of the magnetic anisotropy which is crucial for stabilizing long-range magnetic order at finite temperatures [5].

[1] L. Šmejkal, J. Sinova, T. Jungwirth: Phys. Rev. X 12, 031042 (2022)
[2] L. Šmejkal, J. Sinova, T. Jungwirth: Phys. Rev. X 12, 040501 (2022)
[3] C. Song, H. Bai, Z. Zhou et al.: Nat. Rev. Mater. 10, 473 (2025)
[4] Q. Song, S. Stavrić, P. Barone, A. Droghetti, D. S. Antonenko et al.: Nature 642, 64 (2025)
[5] M. Milivojević, M. Orozović, S. Picozzi, M. Gmitra, S. Stavrić: 2D Mater. 11, 035025 (2024)

У оквиру семинара Центра за изучавање комплексних система Института за физику у Београду, у четвртак, 16. октобра 2025. године у 14 часова у читаоници библиотеке „Др Драган Поповић“, др Ненад Вукмировић (Лабораторија за примену рачунара у науци, Институт за физику у Београду) одржаће предавање:

Grid-Free Evaluation of Phonon-Limited Electronic Relaxation Times and Transport Properties

САЖЕТАК:

This seminar is the first in the series of seminars by the members of the project PolMoReMa [1]. The goals and activities of the project will be briefly presented in the first part of the seminar. In the second part of the seminar, we will present our results on the development of methodology for efficient evaluation of phonon-limited electronic relaxation times and electrical transport properties in semiconducting materials. Namely, present calculations of electrical transport properties of materials require evaluations of electron-phonon coupling constants on dense predefined grids of electron and phonon momenta and performing the sums over these momenta [2, 3]. In this seminar, we present the methodology for calculation of carrier relaxation times and electrical transport properties without the use of a predefined grid [4]. The relaxation times are evaluated by integrating out the delta function that ensures energy conservation and performing an average over the angular components of phonon momentum. The charge carrier mobility is then evaluated as a sum over appropriately sampled electronic momenta. We illustrate our methodology by applying to the Fröhlich model and to a real semiconducting material ZnTe. We find that rather accurate results can be obtained with a modest number of electron and phonon momenta, on the order of one hundred each, regardless of the carrier effective mass.

This research is supported by the Science Fund of the Republic of Serbia, Grant No. 5468, Polaron Mobility in Model Systems and Real Materials – PolMoReMa.

[1] http://polmorema.ipb.ac.rs
[2] S. Poncé, W. Li, S. Reichardt and F. Giustino, Rep. Prog. Phys. 83, 036501 (2020).
[3] N. Vukmirović, Phys. Rev. B 104, 085203 (2021).
[4] N. Vukmirović, Comput. Phys. Commun. 312, 109583 (2025).