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arXiv 2025年

作者： Delgado, Paola C.M. Ganz, Alexander Lin, Chunshan Thériault, Roxane CEICO FZU - Institute of Physics of the Czech Academy of Sciences Na Slovance 1999/2 Prague182 00 Czech Republic Institute for Theoretical Physics Leibniz University Hannover Appelstraße 2 Hannover30167 Germany Faculty of Physics Astronomy and Applied Computer Science Jagiellonian University Krakow30-348 Poland

Scalar particles traveling faster than a subluminal gravitational wave generate gravitons via gravitational Cherenkov radiation. In this paper, we investigate graviton production by the primordial plasma within the framework of modified gravity in the early Universe, generating a relic graviton background. We find that for the minimal model, where only the speed of gravitational waves is modified and a standard model plasma minimally couples to gravity, the relic graviton background can be enhanced by several orders of magnitude, but still agrees with the Big Bang Nucleosynthesis (BBN) bound in most cases. Moreover, we also find that for Horndeski theories, such as Galileon theory, the relic background produced by the thermalized scalar field can reach significant amplitudes, exceeding the BBN bound for a region of the parameter space. By requiring the relic graviton background to remain consistent with the BBN constraint, we derive limits on the gravitational wave speed at early times in these modified gravity theories. Copyright © 2025, The Authors. All rights reserved.

关键词： Gravitational effects

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Antiferromagnetic domains distribution carried by stoichiometry

Antiferromagnetic domains distribution carried by stoichiome...

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2023 IEEE International Magnetic Conference - Short Papers, INTERMAG Short Papers 2023

作者： Mandziak, Anna De La Figuera, Juan Emilio Prieto, Jose Quesada, Adrian Miralles, Cecilia Granados Berja, Alba Aballe, Lucia Foerster, Michael Nino, Miguel Angel Nita, Pawel Solaris Synchrotron Czerwone Maki 98 Cracow30-392 Poland MadridE-28006 Spain MadridE-28049 Spain Alba Synchrotron Light Facility Cells BarcelonaE-08290 Spain Jagiellonian University Faculty of Physics Astronomy and Applied Computer Science ul. prof. Stanislawa Lojasiewicza 11 Cracow30-348 Poland

ISBN: (纸本)9798350338362

We present a spatially resolved X-ray magnetic linear dichroism study of high quality micron-sized mixed nickel-cobalt oxide (NCO) crystals. NixCo1-xO were prepared in-situ by high-temperature oxygen-assisted molecular beam epitaxy on Ru(0001) single crystal. To check the effect of incorporating Ni in the cobalt oxide films, three different composition were prepared. The element specific XMLD measurements reveal strong antiferromagnetic contrast at room temperature and magnetic domains up to one micron wide, reflecting the high structural quality of the islands. By means of vectorial magnetometry, the spin axis orientation of the domains was determined with nanometer spatial resolution, and found to depend on the stoichiometry of prepared crystals. © 2023 IEEE.

关键词： Nickel oxide

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Exploring Environmentally Friendly Corrosion Inhibitors: Insights from Natural and Biomass Residue-Derived Compounds

SSRN

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SSRN 2024年

作者： Othman, Norinsan Kamil Mohammed, Naba Jasim Yusop, Muhammed Rahimi Al-Gburi, Ahmed Jamal Abdullah Materials Science Program Department of Applied Physics Faculty of Science and Technology University Kebangsaan Malaysia Selangor Bangi43600 Malaysia Faculty of Science and Technology School of Chemical Sciences and Food Technology University Kepangsaan Malaysia Selangor Bangi43600 Malaysia Faculty of Electronics and Computer Engineering Universiti Teknikal Malaysia Melaka Hang Tuah Jaya Melaka Durian Tunggal76100 Malaysia

In this investigation, we explored the corrosive effects of date palm seed extracted from natural sources and biomass residues on mild steel in a solution of 0.5 M hydrochloric acid (HCl), employing a combination of experimental and theoretical approaches. Our objective was to scrutinize the interaction of the inhibitor with the metal surface, analyze experimental data, and elucidate how the structural characteristics of the inhibitors influence the corrosion process. The experimental results indicated that as the immersion time and temperature increased, the inhibitory effectiveness declined. Notably, the highest level of inhibition occurred when the concentration of date palm seed extract (DPSE) reached 1100 ppm, showcasing peak inhibitory effects of 95.8% and 97.8% through potentiodynamic polarization and electrochemical impedance spectroscopy techniques, respectively. Additionally, an analysis using X-ray diffraction (XRD) was conducted to scrutinize the chemical composition of the mild steel's surface. The adsorption data were evaluated using adsorption isotherms, revealing that DPSE adhered to the Langmuir adsorption isotherm on the mild steel surface. The Langmuir model exhibited the highest linear regression coefficient value and a slope close to unity. The Gibbs free energy () values suggested that the protection afforded by DPSE involved physical and spontaneous absorption. Examination of the results pertaining to the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) indicated that the carboxyl (COOH) group and the C=C bond were the principal regions exhibiting elevated electron acceptance activity. These components were found to be crucial in the adsorption process on the surface of iron (Fe). © 2024, The Authors. All rights reserved.

关键词： Electrochemical impedance spectroscopy

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Simulating first-order phase transition with hierarchical autoregressive networks

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Physical Review E 2023年第5期107卷 054127-054127页

作者： Piotr Białas Paulina Czarnota Piotr Korcyl Tomasz Stebel Institute of Applied Computer Science Jagiellonian University 30-348 Kraków Poland Faculty of Biochemistry Biophysics and Biotechnology Jagiellonian University 30-387 Kraków Poland Institute of Theoretical Physics Jagiellonian University 30-348 Kraków Poland

We apply the hierarchical autoregressive neural network sampling algorithm to the two-dimensional Q-state Potts model and perform simulations around the phase transition at Q=12. We quantify the performance of the approach in the vicinity of the first-order phase transition and compare it with that of the Wolff cluster algorithm. We find a significant improvement as far as the statistical uncertainty is concerned at a similar numerical effort. In order to efficiently train large neural networks we introduce the technique of pretraining. It allows us to train some neural networks using smaller system sizes and then employ them as starting configurations for larger system sizes. This is possible due to the recursive construction of our hierarchical approach. Our results serve as a demonstration of the performance of the hierarchical approach for systems exhibiting bimodal distributions. Additionally, we provide estimates of the free energy and entropy in the vicinity of the phase transition with statistical uncertainties of the order of 10−7 for the former and 10−3 for the latter based on a statistics of 106 configurations.

关键词： Approximation methods for many-body systems Deep learning Lattice field theory Metropolis algorithm Monte Carlo methods Spin lattice models

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Robust Feature Engineering Techniques for Designing Motor Imagery-Based Bci Systems

SSRN

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SSRN 2025年

作者： Gardezi Ahmed, Syed Saim Khan, Mahnoor Bukhari, Syeda Muneeba Khan, Rizwan Ahmed Jawed, Soyiba Department of Biomedical Engineering Faculty of Engineering Salim Habib University Karachi Pakistan Department of Computer Software Engineering College of Electrical and Mechanical Engineering NUST Islamabad Pakistan Department of Physics Faculty of Applied Sciences Riphah International University Islamabad Pakistan Department of Biomedical Engineering Faculty of Engineering NED University Karachi Pakistan Department of Computer Science Faculty of Information Technology Salim Habib University Karachi Pakistan

A multitude of individuals across the globe grapple with motor disabilities. Neural prosthetics utilizing Brain-computer Interface (BCI) technology exhibit promise for improving motor rehabilitation outcomes. The intricate nature of EEG data poses a significant hurdle for current BCI systems. Recently, a qualitative repository of EEG signals tied to both upper and lower limb execution of motor and motor imagery tasks has been unveiled. Despite this, the productivity of the Machine Learning (ML) Models that were trained on this dataset was alarmingly deficient, and the evaluation framework seemed insufficient. To enhance outcomes, robust feature engineering (signal processing) methodologies are implemented. A collection of time domain, frequency domain, and wavelet-derived features was obtained from 16-channel EEG signals, and the Maximum Relevance Minimum Redundancy (MRMR) approach was employed to identify the four most significant features. For classification K Nearest Neighbors, Support Vector Machine, Decision Tree, and Naive Bayes models were implemented with these selected features, evaluating their effectiveness through metrics such as testing accuracy, precision, recall, and F1 Score. By leveraging SVM with a Gaussian Kernel, a remarkable maximum testing accuracy of 92.50% for motor activities and 95.48% for imagery activities is achieved. These results are notably more dependable and gratifying compared to the previous study, where the peak accuracy was recorded at 74.36%. This research work provide an in-depth analysis of the MI Limb EEG dataset and it will help in designing and developing simple, cost-effective and reliable BCI systems for neuro-rehabilitation. © 2025, The Authors. All rights reserved.

关键词： Image enhancement

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Development and study of the impacts of automated walking aids on the elderly 20

Development and study of the impacts of automated walking ai...

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20th International Conference on Electrical Engineering/Electronics, computer, Telecommunications and Information Technology, ECTI-CON 2023

作者： Tangjitjetsada, Maleeya Thianthong, Tawan Rakluea, Chawalit Loedhammacakra, Wisit Rakluea, Paitoon Tangthong, Nipont Mahatthanajatuphat, Chatree Chudpooti, Nonchanutt Rajamangala University of Technology Suvarnabhumi Faculty of Engineering and Architecture Department of Electronics and Telecommunication Engineering Nonthaburi Thailand Siam Airport Ground Services Co. Ltd Bangkok Thailand Rajamangala University of Technology Thanyaburi Faculty of Engineering Department of Electronics and Telecommunication Engineering Pathum Thani Thailand King Mongkut's University of Technology North Bangkok Faculty of Engineering Department of Electrical and Computer Engineering Bangkok Thailand King Mongkut's University of Technology North Bangkok Faculty of Applied Science Department of Industrial Physics and Medical Instrumentation Bangkok Thailand

ISBN: (纸本)9798350310467

Since Thailand has now completely stepped into an aged society there are more than 20% of the population aged 60 years and over. There was also an increase in those who had problems with their balance. One of the main difficulties for these people is walking on their own. This paper presents an automatic walking aid for people with balance or walking problems. A specially designed automatic walking aid can be adjusted to six levels of height. It has an anti-collision warning system at a distance of up to 40 centimeters and displays GPS coordinates via SMS when falling. The experimental results of the prototype automatic walking aid showed that the walking aid could work as designed and could help people with balance problems walk more comfortably. © 2023 IEEE.

关键词： Walking aids

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Radiation-dominated bouncing model with slow contraction and inflation

引用

Physical Review D 2024年第4期109卷 043531-043531页

作者： Piero A. P. Molinari Paola C. M. Delgado Rodrigo F. Pinheiro Nelson Pinto-Neto Centro Brasileiro de Pesquisas Físicas - CBPF Rua Dr. Xavier Sigaud 150 Urca 22290-180 Rio de Janeiro RJ Brazil Faculty of Physics Astronomy and Applied Computer Science Jagiellonian University 30-348 Krakow Poland

A very simple nonsingular inflationary model is presented where the unique matter content is a radiation fluid. The model slowly contracts from a very large, almost empty and flat spacetime and realizes a bounce. It is then launched to a quasi-de Sitter inflationary expansion with more than sixty e-folds, which smoothly changes to the usual classical, decelerated radiation-dominated expansion before nucleosynthesis. The initial contracting and final expanding phases are classical, but the intermediate bounce and inflationary phases are induced by quantum cosmological effects emerging from a Gaussian wave function quickly moving in configuration space. During this quantum era, a huge number of photons is created. The scale factor describing all this rich evolution is a surprisingly simple analytic function of conformal time. The cosmological scalar perturbations arising from quantum vacuum fluctuations in the far past of the model present an almost scale invariant spectrum with an amplitude compatible with observations for reasonable values of the free parameters of the model.

关键词： Canonical quantum gravity Cosmology Inflation Quantum cosmology

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Enhancement and anisotropy of electron Landé factor due to spin-orbit interaction in semiconductor nanowires

arXiv

引用

arXiv 2023年

作者： Czarnecki, Julian Bertoni, Andrea Goldoni, Guido Wójcik, Pawel AGH University of Krakow Faculty of Physics and Applied Computer Science al. A. Mickiewicza 30 Krakow30-059 Poland CNR-NANO S3 Istituto Nanoscienze Via Campi 213/a Modena41125 Italy Department of Physics Informatics and Mathematics University of Modena and Reggio Emilia via Campi 213/a Modena41125 Italy

We investigate the effective Landé factor in semiconductor nanowires with strong Rashba spin-orbit coupling. Using the k · p theory and the envelope function approach we derive a conduction band Hamiltonian where g∗ is explicitly related to the spin-orbit coupling contants αR. Our model includes orbital effects from the Rashba spin-orbit term, leading to a significant enhancement of the effective Landé factor which is naturally anisotropic. For nanowires based on the low-gap, high spin-orbit coupled material InSb, we investigate the anisotropy of the effective Landé factor with respect to the magnetic field direction, exposing a twofold symmetry for the bottom gate architecture. The anisotropy results from the competition between the localization of the envelope function and the spin polarization of the electronic state, both determined by the magnetic field direction. Copyright © 2023, The Authors. All rights reserved.

关键词： Anisotropy

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Holes in Convex and Simple Drawings 32

Holes in Convex and Simple Drawings

引用

32nd International Symposium on Graph Drawing and Network Visualization, GD 2024

作者： Bergold, Helena Orthaber, Joachim Scheucher, Manfred Schröder, Felix Institute of Computer Science Freie Universität Berlin Germany TUM School of Computation Information and Technology Technische Universität München Germany Institute of Software Technology Graz University of Technology Austria Institut Für Mathematik Technische Universität Berlin Germany Department of Applied Mathematics Faculty of Mathematics and Physics Charles University Prague Czech Republic Institute of Mathematics Technische Universität Berlin Germany

ISBN: (纸本)9783959773430

Gons and holes in point sets have been extensively studied in the literature. For simple drawings of the complete graph a generalization of the Erdos-Szekeres theorem is known and empty triangles have been investigated. We introduce a notion of k-holes for simple drawings and study their existence with respect to the convexity hierarchy. We present a family of simple drawings without 4-holes and prove a generalization of Gerken's empty hexagon theorem for convex drawings. A crucial intermediate step will be the structural investigation of pseudolinear subdrawings in convex drawings. © Helena Bergold, Joachim Orthaber, Manfred Scheucher, and Felix Schröder.

关键词： Geometry

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Pseudo-observables and Deep Neural Network for mixed CP H → ττ decays at LHC

arXiv

引用

arXiv 2024年

作者： Richter-Was, E. Yerniyazov, T. Was, Z. Institute of Physics Jagiellonian University Lojasiewicza 11 Kraków30-348 Poland Faculty of Physics Astronomy and Applied Computer Science Jagiellonian University Lojasiewicza 11 Kraków30-348 Poland Institute of Nuclear Physics IFJ-PAN Radzikowskiego 152 Kraków31-342 Poland

The consecutive steps of cascade decay initiated by H → ττ can be useful for the measurement of Higgs couplings and in particular of the Higgs boson parity. The standard analysis method applied so far by ATLAS and CMS Collaborations was to fit a one-dimensional distribution of the angle between reconstructed decay planes of the τ lepton decays, ∗, which is sensitive to transverse spin correlations of the τ decays and, hence, to the CP state mixing angle, CP. Machine Learning techniques (ML) offer opportunities to manage such complex multidimensional signatures. The multidimensional signatures, the 4-momenta of the τ decay products can be used directly as input information to the machine learning algorithms to predict the CP-sensitive pseudo-observables and/or provide discrimination between different CP hypotheses. In the previous papers, we have shown that multidimensional signatures, the 4-momenta of the τ decay products can be used as input information to the machine learning algorithms to predict the CP-sensitive pseudo-observables and/or provide discrimination between different CP hypotheses. In this paper we show how the classification or regression methods can be used to train an ML model to predict the spin weight sensitive to the CP state of the decaying Higgs boson, parameters of the functional form of the spin weight, or the most preferred CP mixing angle of the analysed sample. The one-dimensional distribution of the predicted spin weight or the most preferred CP mixing angle of the experimental data can be examined further, with the statistical methods, to derive the measurement of the CP mixing state of the Higgs signal events in decay H → ττ. This paper extends studies presented in our previous publication, with more experimentally realistic scenarios for the features lists and further development of strategies how proposed pseudo-observables can be used in the measurement. Copyright © 2024, The Authors. All rights reserved.

关键词： Bosons

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