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On Voronoi visibility maps of 1.5D terrains with multiple viewpoints

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arXiv 2023年

作者： Keikha, Vahideh Saumell, Maria The Czech Academy of Sciences Institute of Computer Science Czech Republic Faculty of Mathematics and Physics Department of Applied Mathematics Charles University Prague Czech Republic Department of Theoretical Computer Science Faculty of Information Technology Czech Technical University Prague Czech Republic

Given an n-vertex 1.5D terrain T and a set P of m 2 + kc) log n) time, where kc and kv denote the total complexity of ColVis(T, P) and VorVis(T, P), respectively. This improves upon a previous algorithm for this problem. We also generalize our algorithm to higher order Voronoi visibility maps, and to Voronoi visibility maps with respect to other distances. Finally, we prove bounds relating kv to kc, and we show an application of our algorithm to a problem on limited range of sight. © 2023, CC BY.

关键词： Visibility

Interplay between the extended s-wave symmetry of the gap and the spin-orbit coupling in the low-electron concentration regime of quasi-two-dimensional superconductors

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arXiv 2022年

作者： Zegrodnik, Michal Wójcik, P. Academic Centre for Materials and Nanotechnology AGH University of Science and Technology Al. Mickiewicza 30 Krakow30-059 Poland AGH University of Science and Technology Faculty of Physics and Applied Computer Science Krakow30-059 Poland Al. Mickiewicza 30 Krakow30-059 Poland

We analyze the real-space paired state with the k-dependent superconducting gap in the presence of Rashba type spin-orbit coupling and external magnetic field. We show that the extended s-wave pairing symmetry is the most probable scenario to appear in the low-electron concentration regime. According to our study, the van Hove singularity induced by the spin-orbit coupling may lead to a significant enhancement of the superconducting gap, critical temperature and critical magnetic field. Moreover, the combined effect of the spin-orbit coupling and the external magnetic field results in a non-zero total momentum of the Cooper pairs, which is a characteristic feature of the so-called helical state. In such situation, due to the C4 symmetry breaking, a small d-wave and p-wave contributions to the pairing appear, which significantly change the character of the helical state. The obtained results are discussed in the context of the experimental data related with the unconventional superconducting features of the transition metal oxide interfaces as well as the recently reported supercurrent diode effect. Copyright © 2022, The Authors. All rights reserved.

关键词： Transition metals

Disformal symmetry in the Universe: mimetic gravity and beyond

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arXiv 2023年

作者： Domènech, Guillem Ganz, Alexander Institute for Theoretical Physics Leibniz University Hannover Appelstraße 2 Hannover30167 Germany Faculty of Physics Astronomy and Applied Computer Science Jagiellonian University Krakow30-348 Poland

Symmetries play an important role in fundamental physics. In gravity and field theories, particular attention has been paid to Weyl (or conformal) symmetry. However, once the theory contains a scalar field, conformal transformations of the metric can be considered a subclass of a more general type of transformation, so-called disformal transformation. Here, we investigate the implications of pure disformal symmetry in the Universe. We derive the form of general disformal invariant tensors from which we build the most general disformal invariant action. We argue that, in cosmology, disformal symmetry amounts to require that the lapse function is fully replaced by a (time-like) scalar field at the level of the action. We then show that disformal symmetry is in general an exactly equivalent formulation of general mimetic gravity. Lastly, we go beyond mimetic gravity and find that a particular class of invariance leads to seemingly Ostrogradski-like (with higher derivatives) Lagrangians, which are nevertheless absent of Ostrogradski ghosts in a cosmological background, despite having an additional degree of freedom. We also propose an application of our formalism to find new invertible disformal transformations, where the coefficient involves higher derivatives and curvature, further expanding the theory space of scalar-tensor theories. Copyright © 2023, The Authors. All rights reserved.

关键词： Tensors

Kinetics of transformation, border of metastable miscibility gap in Fe-Cr alloy and limit of Cr solubility in iron at 858 K

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arXiv 2022年

作者： Dubiel, Stanislaw M. Żukrowski, Jan AGH University of Science and Technology Faculty of Physics and Applied Computer Science al. A. Mickiewicza 30 Kraków30-059 Poland AGH University of Science and Technology Academic Center for Materials and Nanotechnology al. A. Mickiewicza 30 Kraków30-059 Poland

The study was aimed at determination of the position of the Fe-rich border of the metastable miscibility gap (MMG) and of the solubility limit of Cr in iron at 858 K. Towards this end a Fe73.7Cr26.3 alloy was isothermally annealed at 858 K in vacuum up to 8144 hours and Mössbauer spectra were recorded at room temperature after every step of the annealing. Three spectral parameters viz. the average hyperfine field, , the average isomer shift, , and the probability of the atomic configuration with no Cr atoms in the two-shell vicinity of the probe Fe atoms, P(0,0), gave evidence that the transformation process takes place in two stages. All three parameters could have been well described in terms of the Johnson-Mehl-Avrami-Kolmogorov equation, yielding kinetics parameters. The first stage, associated with the phase decomposition, proceeded much faster than the second stage, associated with the alpha-to-sigma phase transformation. The most reliable estimation of the position of the MMG and that of the value of the Cr solubility limit was obtained from the annealing time dependence of , namely 24.5 at.% Cr for the former and 20.3 at.% Cr for the latter. A comparison of these figures with the recent phase diagrams pertinent to Fe-Cr system was done. © 2022, CC BY-NC-ND.

关键词： Binary alloys

Testing Discrete Symmetries in Ortho-Positronium Decays with the J-PET Detector

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arXiv 2023年

作者： Nski, Eryk Czerwi Marian Smoluchowski Institute of Physics Faculty of Physics Astronomy and Applied Computer Science Jagiellonian University Kraków30-348 Poland Center for Theranostics Jagiellonian University Kraków Poland

A first result related to a CPT test in the decay of ortho-positronium based on data collected by means of the J-PET detector is already available,1 and a new test of CP symmetry is under investigation.2 Both results are based on the determination of angular correlations between momenta of gamma rays and other vector properties of the investigated system.3 Here, arguments for the possible usage of data collected by the J-PET group to test CPT symmetry within the Standard-Model Extension framework4 are shortly presented. © 2023, CC BY.

关键词： Gamma rays

Strong-coupling superconductivity of SrIr2 and SrRh2: Phonon engineering of metallic Ir and Rh

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Physical Review B 2021年第5期104卷 054505-054505页

作者： Sylwia Gutowska Karolina Górnicka Paweł Wójcik Tomasz Klimczuk Bartlomiej Wiendlocha Faculty of Physics and Applied Computer Science AGH University of Science and Technology Aleja Mickiewicza 30 30-059 Krakow Poland Faculty of Applied Physics and Mathematics and Advanced Materials Centre Gdansk University of Technology ul. Narutowicza 11/12 80-233 Gdańsk Poland

Experimental and theoretical studies on superconductivity in SrIr2 and SrRh2 Laves phases are presented. The measured resistivity, heat capacity, and magnetic susceptibility confirm the superconductivity of these compounds with Tc=6.07 and 5.41 K, respectively. Electronic structure calculations show that the Fermi surface is mostly contributed by 5d (4d) electrons of Ir (Rh), with Sr atoms playing the role of electron donors. The effect of the spin-orbit coupling is analyzed and found to be important in both materials. Lattice dynamics and electron-phonon coupling (EPC) are studied and the strong electron-phonon interaction is found, contributed mostly by the low-frequency Ir and Rh vibrations. The enhancement of EPC, when compared to weakly coupled metallic Ir and Rh, is explained by the strong modifications in the propagation of phonons in the network of Ir (Rh) tetrahedrons, which are the building blocks of the Laves phase, and originate from the metallic fcc structures of elemental iridium and rhodium.

关键词： Electron-phonon coupling Electronic structure Superconductivity Transition metals Density functional theory

Rényi entanglement entropy of a spin chain with generative neural networks

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Physical Review E 2024年第4期110卷 044116页

作者： Piotr Białas Piotr Korcyl Tomasz Stebel Dawid Zapolski Institute of Applied Computer Science <a href="https://***/03bqmcz70">Jagiellonian University</a> ul. Łojasiewicza 11 30-348 Kraków Poland. Institute of Theoretical Physics <a href="https://***/03bqmcz70">Jagiellonian University</a> ul. Łojasiewicza 11 30-348 Kraków Poland. Faculty of Mathematics and Computer Science <a href="https://***/03bqmcz70">Jagiellonian University</a> ul. Łojasiewicza 6 30-348 Kraków Poland.

We describe a method to estimate Rényi entanglement entropy of a spin system which is based on the replica trick and generative neural networks with explicit probability estimation. It can be extended to any spin system or lattice field theory. We demonstrate our method on a one-dimensional quantum Ising spin chain. As the generative model, we use a hierarchy of autoregressive networks, allowing us to simulate up to 32 spins. We calculate the second Rényi entropy and its derivative and cross-check our results with the numerical evaluation of entropy and results available in the literature.

关键词： Entanglement entropy Quantum statistical mechanics Deep learning Information theory Ising model Monte Carlo methods Neural network simulations

A Comprehensive Study of Double pion Photoproduction: A Regge Approach 10

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A Comprehensive Study of Double pion Photoproduction: A Regg...

10th International Conference on Quarks and Nuclear physics, QNP 2024

作者： Hammoud, Nadine Bibrzycki, Lukasz Mathieu, Vincent Perry, Robert J. Szczepaniak, Adam P. Departament de Física Quàntica i Astrofísica Institut de Ciències del Cosmos Universitat de Barcelona BarcelonaE-08028 Spain AGH University of Krakow Faculty of Physics and Applied Computer Science al. Mickiewicza 30 KrakówPL-30059 Poland Departamento de Física Teórica Universidad Complutense de Madrid IPARCOS MadridE-28040 Spain Theory Center Thomas Jefferson National Accelerator Facility Newport NewsVA23606 United States Center for Exploration of Energy and Matter Indiana University BloomingtonIN47403 United States Department of Physics Indiana University BloomingtonIN47405 United States

Presented here is a theoretical model designed to investigate double pion photoproduction, within the photon energy range of 3.0 to 3.8 GeV and momentum transfer range of 0.4 2. This model integrates contributions from resonances such as the ρ(770), as well as the primary background from the Deck mechanism. Utilizing the Regge formalism and incorporating the established Deck mechanism, the model emphasizes the significance of the ρ(770) resonance, highlighting its role in representing P-wave contributions arising from pomeron alongside other exchanges. However, at high momentum transfers, indications of s-channel helicity non-conservation emerge, suggesting the involvement of additional partial waves, notably the S and D waves. The model is further extended to include scalar mesons such as f0(500), f0(980), and f0(1370), along with the tensor meson f2(1270), influencing S- and D-wave effects, respectively. Predictions of angular moments are compared with CLAS data, and the analysis further explores the t-dependence of the Regge amplitude residue function for subdominant exchanges. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0).

关键词： Momentum transfer

The In-Plane Band Bending Effect Around AU Islands Grown on the Bi2te3 Topological Insulator

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SSRN

SSRN 2023年

作者： Naumov, Andrii Chrobak, Maciej Trembulowicz, Artur Jurczyszyn, Michal Maćkosz, Krzysztof Stępień, Joanna Sikora, Marcin Przybylski, Marek Academic Centre for Materials and Nanotechnology Poland Faculty of Physics and Applied Computer Science AGH University of Krakow Mickiewicza Av. 30 Krakow30-059 Poland Institute of Experimental Physics University of Wroclaw pl. M. Borna 9 Wroclaw50-204 Poland Empa-Swiss Federal Laboratories for Materials Science and Technology Laboratory for Mechanics of Materials and Nanostructures Feuerwerkerstrasse 39 ThunCH-3602 Switzerland AGH University of Science and Technology Poland

We have utilized scanning tunneling microscopy and spectroscopy (STM/STS) as well as x-ray linear dichroism (XLD) along with DFT calculations to determine the structural and electronic changes of the gold-covered nonstoichiometric Bi2Te3 single crystal surface. XLD spectra supported by a numerical simulation of several configurations show that at low coverage ( 1.0 ML) mixing at the Au/Bi2Te3 interface may occur. For local electronic characterization around stand-alone Au islands, small coverages were selected for which the inter-island distance is large enough to avoid overlapping island-wide effects. STS spectra reveal that for small coverages the topological surface states (TSS) are preserved. However, at a distance of about 10 nm from an Au island, by approaching the islands, the electronic structure gradually changes. This is manifested by a gradual shift of the STS spectra to more negative energies with respect to the pristine surface. The results are discussed in view of possible Au-Bi2Te3 mixing, a local charge transfer and the presence of in-plane downward band bending. © 2023, The Authors. All rights reserved.

关键词： Electronic structure