У оквиру семинара Центра за физику чврстог стања и нове материјале Института за физику у Београду, у уторак, 10. јуна 2025. године у 13 часова у читаоници библиотеке „Др Драган Поповић“, проф. Али Генчер (Универзитет у Анкари, Центар за примену и истраживања суперпроводничких технологија) одржаће предавање:

Influence of Reaction Kinetics on MgB2 Wires with Enhanced Properties: Optimization of Copper-Coated Magnesium Rod and Carbon-Coated Nano-Boron Powders in IMD Process

САЖЕТАК:

Magnesium diboride (MgB₂) wires fabricated by Internal Magnesium Diffusion (IMD) process are of renewed recent interest for potential superconducting applications due to their improved superconducting properties with flux pinning, high critical temperature (Tc ≈ 39 K), cost-effectiveness, and potential for large-scale production. This talk focuses on the impacts of varying copper coatings on magnesium rods and the incorporation of different carbon-coated boron powders with experimental works on the microstructural and superconducting properties of MgB₂ wires. By systematically varying the copper coating content on Mg rods at various percentages and the carbon coated boron powder precursors, we aim to optimize the enhanced critical current density (Jc) especially in the applied magnetic fields. Characterization techniques such as optical microscopy, scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS), DTA analysis for reaction kinetics and electrical transport measurements were carried out to investigate the effects of porosity, grain connectivity, morphology, and superconducting physical properties of the MgB₂ wires.

The results show that both carbon and copper doping play an important role in enhancing flux pinning by introducing nanoscale defects and impurities that act as pinning centers for the vortices. However, excessive doping or improper copper coating thickness can lead to the formation of unwanted secondary phases and defects, which may a negative effect the superconducting properties and mechanical stability.

In conclusion, this study provides valuable insights into optimizing the IMD process for the fabrication of high performance MgB₂ wires. By balancing the thickness of the copper coating and the concentration of
carbon doping, improved superconducting properties can be achieved, making the processed MgB₂ wires highly suitable for applications such as magnetic resonance imaging (MRI), particle accelerators, and high-field magnets. Experimental results with model dependent analysis will be presented to achieve higher critical current density at fields exceeding from 1 to 12 T.

This work has been supported by TÜBİTAK and Chinese Academy of Sciences (CAS) via Bilateral Cooperation under contract No: 123N624

У оквиру семинара Strings, Holography & Chaos, у среду, 11. јуна 2025. године у 12 часова путем Zoom платформе, Хуан Педраза (Институт за теоријску физику UAM/CSIC, Мадрид, Шпанија) одржаће предавање:

A holographic look into the black hole interior

САЖЕТАК:

Holography provides a powerful framework for probing the intricate structure of black hole interiors. Remarkably, the seminal BKL analysis from the early ’70s has recently found a natural realization within AdS/CFT, offering a way to obtain and study Kasner-like dynamics inside AdS black holes. In this talk, I’ll discuss how these behaviors manifest in the dual CFT as exotic RG flows, and how CFT observables can sometimes capture — or fail to capture — the physics near the singularity. I will highlight various probes, including the thermal c-function, two-sided correlators, and holographic complexity. Time permitting, I will also touch on the role of higher-derivative corrections and their impact on the structure of deep interiors.

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Meeting ID: 927 0226 2512
Passcode: 658229

У оквиру семинара Центра за изучавање комплексних система Института за физику у Београду, у четвртак, 5. јуна 2025. године у 14 часова у сали „Звонко Марић“ Института за физику у Београду, др Марија Шиндик (Центар за изучавање комплексних система, Институт за физику у Београду) одржаће предавање:

Sound in Dipolar Supersolids

САЖЕТАК:

Supersolid is an intriguing state of matter characterized by the spontaneous and simultaneous breaking of phase and continuous translational symmetry, resulting in the non-intuitive coexistence of superfluid and crystalline features. This phase has recently been realized experimentally in dipolar Bose-Einstein condensates. In one-dimensional ring-trap geometries, superolids exhibit two Goldstone modes, which can be excited by the sudden removal of a weak periodic perturbation. In this talk we will present a numerical investigation of the resulting collective oscillations using the extended Gross-Pitaevskii theory and extract the corresponding sound velocities. Comparing these with predictions from supersolid hydrodynamic theory will enable us to identify the superfluid fraction –  a key parameter characterizing the supersolid phase. In the presence of persistent currents, the excitation spectrum is modified by a Doppler effect, resulting in a doubling of the sound velocities. We will demonstrate that the Doppler shifts differ for the two modes, with analytical predictions from hydrodynamics showing good agreement with Gross-Pitaevskii simulations.

У оквиру семинара Групе за гравитацију, честице и поља, у петак, 30. маја 2025. године у 11:15 у сали 360 Института за физику у Београду, др Горан Ђорђевић (Природно-математички факултет, Универзитет у Нишу) одржаће предавање:

Scaling Invariance of Perturbations in k-Inflation Models

САЕЖТАК:

The study of the background and perturbations in k-essence inflation models is presented. It is shown that a general k-essence exhibits a simple scaling property. The accent is given on study of the two classes of k-inflation models with the potential characterized by an inflection point. This study allow to redefine input parameters so that the perturbations spectra satisfy the correct normalization at the CMB
pivot scale. The background and perturbation equations are integrated numerically for two specific models. The abundance of primordial black holes today within the two models is briefly reviewed.

У оквиру семинара Центра за изучавање комплексних система Института за физику у Београду, у уторак, 27. маја 2025. у 14 часова у читаоници библиотеке „Др Драган Поповић“, проф. др Мигел А. Ф. Санхуан (Универзитет Реј Хуан Карлос, Мадрид, Шпанија) одржаће предавање:

Symphony of the uncertainty in three movements

САЖЕТАК:

In this talk, akin to a symphony in three movements, we will provide an overview of various concepts related to uncertainty and unpredictability in nonlinear dynamics. We will start from the topological concept of indecomposable continua to Wada basins. Then, we will continue with the Wada basins of the Hénon-Heiles Hamiltonian system, to finally culminate with the concept of basin entropy. Additionally, we will discuss recent advancements in using basin entropy for classifying basins, as well as for exploring bifurcations.

[1] J. Aguirre, R. L. Viana, and M. A. F. Sanjuán, Rev. Mod. Phys. 81, 333 (2009).
[2] A. Daza, A. Wagemakers, B. Georgeot et al., Sci. Rep. 6, 31416 (2016).
[3] A. Daza, A. Wagemakers, and M. A. F. Sanjuán, EPL 141, 43001 (2023).
[4] A. Daza, A. Wagemakers, and M. A. F. Sanjuán, Chaos Solit. Fractals 159, 112112 (2022).
[5] A. Wagemakers, A. Daza, and M. A. F. Sanjuán. Chaos Solit. Fractals 175, 113963 (2023).
[6] A. Daza, A. Wagemakers, and M. A. F. Sanjuán, Phys. Today 77, 44 (2024).

У оквиру семинара Групе за гравитацију, честице и поља, у петак, 23. маја 2025. године у 11:15 у сали 360 Института за физику у Београду, др Биљана Николић (Физички факултет, Универзитет у Београду) одржаће предавање:

Homological quantization of scalar electrodynamics

САЖЕТАК:

Costello and Gwilliam developed an algebraic version of Batalin-Vilkoviski quantization, which provides an alternative to the path integral formalism for computing Green’s functions of gauge field theories. This method is suitable for generalization to the non-commutative case with so-called braided noncommutativity. I will present methods of homological quantization in the commutative setting and will consider an example of scalar electrodynamics.