First conceptualised in Olaf Stapledon's 1937 novel 'Star Maker', before being popularised by Freeman Dyson in the 1960s, Dyson Spheres are structures which surround a civilisation's sun to collect all the energy being radiated. This article presents a discussion of the features of such a feat of engineering, reviews the viability, scale and likely design of a Dyson structure, and analyses details about each stage of its construction and operation. It is found that a Dyson Swarm, a large array of individual satellites orbiting another celestial body, is the ideal design for such a structure as opposed to the solid sun-surrounding structure which is typically associated with the Dyson Sphere. In our solar system, such a structure based around Mars would be able to generate the Earth's 2019 global power consumption of 18.35 TW within fifty years once its construction has begun, which itself could start by 2040 using biennial launch windows. Alongside a 4.17 km2 ground-based heliostat array, the swarm of over 5.5 billion satellites would be constructed on the surface of Mars before being launched by electromagnetic accelerators into a Martian orbit. Efficiency of the Dyson Swarm ranges from 0.74–2.77% of the Sun's 3.85 × 1026 W output, with large potential for growth as both current technologies improve, and future concepts are brought to reality in the time before and during the swarm's construction. Not only would a Dyson Swarm provide a near-infinite, renewable power source for Earth, it would also allow for significant expansions in human space exploration and for our civilisation as a whole.
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Jack Smith 2022 Phys. Scr. 97 122001
S B Dugdale 2016 Phys. Scr. 91 053009
The concept of the Fermi surface is at the very heart of our understanding of the metallic state. Displaying intricate and often complicated shapes, the Fermi surfaces of real metals are both aesthetically beautiful and subtly powerful. A range of examples is presented of the startling array of physical phenomena whose origin can be traced to the shape of the Fermi surface, together with experimental observations of the particular Fermi surface features.
Gerard 't Hooft et al 2024 Phys. Scr. 99 052501
Despite its amazing quantitative successes and contributions to revolutionary technologies, physics currently faces many unsolved mysteries ranging from the meaning of quantum mechanics to the nature of the dark energy that will determine the future of the Universe. It is clearly prohibitive for the general reader, and even the best informed physicists, to follow the vast number of technical papers published in the thousands of specialized journals. For this reason, we have asked the leading experts across many of the most important areas of physics to summarise their global assessment of some of the most important issues. In lieu of an extremely long abstract summarising the contents, we invite the reader to look at the section headings and their authors, and then to indulge in a feast of stimulating topics spanning the current frontiers of fundamental physics from 'The Future of Physics' by William D Phillips and 'What characterises topological effects in physics?' by Gerard 't Hooft through the contributions of the widest imaginable range of world leaders in their respective areas. This paper is presented as a preface to exciting developments by senior and young scientists in the years that lie ahead, and a complement to the less authoritative popular accounts by journalists.
Ulrik L Andersen et al 2016 Phys. Scr. 91 053001
Squeezed light generation has come of age. Significant advances on squeezed light generation have been made over the last 30 years—from the initial, conceptual experiment in 1985 till today's top-tuned, application-oriented setups. Here we review the main experimental platforms for generating quadrature squeezed light that have been investigated in the last 30 years.
Anton Zeilinger 2017 Phys. Scr. 92 072501
The quantum physics of light is a most fascinating field. Here I present a very personal viewpoint, focusing on my own path to quantum entanglement and then on to applications. I have been fascinated by quantum physics ever since I heard about it for the first time in school. The theory struck me immediately for two reasons: (1) its immense mathematical beauty, and (2) the unparalleled precision to which its predictions have been verified again and again. Particularly fascinating for me were the predictions of quantum mechanics for individual particles, individual quantum systems. Surprisingly, the experimental realization of many of these fundamental phenomena has led to novel ideas for applications. Starting from my early experiments with neutrons, I later became interested in quantum entanglement, initially focusing on multi-particle entanglement like GHZ states. This work opened the experimental possibility to do quantum teleportation and quantum hyper-dense coding. The latter became the first entanglement-based quantum experiment breaking a classical limitation. One of the most fascinating phenomena is entanglement swapping, the teleportation of an entangled state. This phenomenon is fundamentally interesting because it can entangle two pairs of particles which do not share any common past. Surprisingly, it also became an important ingredient in a number of applications, including quantum repeaters which will connect future quantum computers with each other. Another application is entanglement-based quantum cryptography where I present some recent long-distance experiments. Entanglement swapping has also been applied in very recent so-called loophole-free tests of Bell's theorem. Within the physics community such loophole-free experiments are perceived as providing nearly definitive proof that local realism is untenable. While, out of principle, local realism can never be excluded entirely, the 2015 achievements narrow down the remaining possibilities for local realistic explanations of the quantum phenomenon of entanglement in a significant way. These experiments may go down in the history books of science. Future experiments will address particularly the freedom-of-choice loophole using cosmic sources of randomness. Such experiments confirm that unconditionally secure quantum cryptography is possible, since quantum cryptography based on Bell's theorem can provide unconditional security. The fact that the experiments were loophole-free proves that an eavesdropper cannot avoid detection in an experiment that correctly follows the protocol. I finally discuss some recent experiments with single- and entangled-photon states in higher dimensions. Such experiments realized quantum entanglement between two photons, each with quantum numbers beyond 10 000 and also simultaneous entanglement of two photons where each carries more than 100 dimensions. Thus they offer the possibility of quantum communication with more than one bit or qubit per photon. The paper concludes discussing Einstein's contributions and viewpoints of quantum mechanics. Even if some of his positions are not supported by recent experiments, he has to be given credit for the fact that his analysis of fundamental issues gave rise to developments which led to a new information technology. Finally, I reflect on some of the lessons learned by the fact that nature cannot be local, that objective randomness exists and about the emergence of a classical world. It is suggestive that information plays a fundamental role also in the foundations of quantum physics.
S Pfalzner et al 2015 Phys. Scr. 90 068001
The solar system started to form about 4.56 Gyr ago and despite the long intervening time span, there still exist several clues about its formation. The three major sources for this information are meteorites, the present solar system structure and the planet-forming systems around young stars. In this introduction we give an overview of the current understanding of the solar system formation from all these different research fields. This includes the question of the lifetime of the solar protoplanetary disc, the different stages of planet formation, their duration, and their relative importance. We consider whether meteorite evidence and observations of protoplanetary discs point in the same direction. This will tell us whether our solar system had a typical formation history or an exceptional one. There are also many indications that the solar system formed as part of a star cluster. Here we examine the types of cluster the Sun could have formed in, especially whether its stellar density was at any stage high enough to influence the properties of today's solar system. The likelihood of identifying siblings of the Sun is discussed. Finally, the possible dynamical evolution of the solar system since its formation and its future are considered.
Kaj Sotala and Roman V Yampolskiy 2015 Phys. Scr. 90 018001
Many researchers have argued that humanity will create artificial general intelligence (AGI) within the next twenty to one hundred years. It has been suggested that AGI may inflict serious damage to human well-being on a global scale ('catastrophic risk'). After summarizing the arguments for why AGI may pose such a risk, we review the fieldʼs proposed responses to AGI risk. We consider societal proposals, proposals for external constraints on AGI behaviors and proposals for creating AGIs that are safe due to their internal design.
Gerianne Alexander et al 2020 Phys. Scr. 95 062501
Sounds of Science is the first movement of a symphony for many (scientific) instruments and voices, united in celebration of the frontiers of science and intended for a general audience. John Goodenough, the maestro who transformed energy usage and technology through the invention of the lithium-ion battery, opens the programme, reflecting on the ultimate limits of battery technology. This applied theme continues through the subsequent pieces on energy-related topics—the sodium-ion battery and artificial fuels, by Martin Månsson—and the ultimate challenge for 3D printing, the eventual production of life, by Anthony Atala. A passage by Gerianne Alexander follows, contemplating a related issue: How might an artificially produced human being behave? Next comes a consideration of consciousness and free will by Roland Allen and Suzy Lidström. Further voices and new instruments enter as Warwick Bowen, Nicolas Mauranyapin and Lars Madsen discuss whether dynamical processes of single molecules might be observed in their native state. The exploitation of chaos in science and technology, applications of Bose–Einstein condensates and the significance of entropy follow in pieces by Linda Reichl, Ernst Rasel and Roland Allen, respectively. Mikhail Katsnelson and Eugene Koonin then discuss the potential generalisation of thermodynamic concepts in the context of biological evolution. Entering with the music of the cosmos, Philip Yasskin discusses whether we might be able to observe torsion in the geometry of the Universe. The crescendo comes with the crisis of singularities, their nature and whether they can be resolved through quantum effects, in the composition of Alan Coley. The climax is Mario Krenn, Art Melvin and Anton Zeilinger's consideration of how computer code can be autonomously surprising and creative. In a harmonious counterpoint, his 'Guidelines for considering AIs as coauthors', Roman Yampolskiy concludes that code is not yet able to take responsibility for coauthoring a paper. An interlude summarises a speech by Zdeněk Papoušek. In a subsequent movement, new themes emerge as we seek to comprehend how far we have travelled along the path to understanding, and speculate on where new physics might arise. Who would have imagined, 100 years ago, a global society permeated by smartphones and scientific instruments so sophisticated that genes can be modified and gravitational waves detected?
Michael G Raymer and Ian A Walmsley 2020 Phys. Scr. 95 064002
We review the concepts of temporal modes (TMs) in quantum optics, highlighting Roy Glauber's crucial and historic contributions to their development, and their growing importance in quantum information science. TMs are orthogonal sets of wave packets that can be used to represent a multimode light field. They are temporal counterparts to transverse spatial modes of light and play analogous roles—decomposing multimode light into the most natural basis for isolating statistically independent degrees of freedom. We discuss how TMs were developed to describe compactly various processes: superfluorescence, stimulated Raman scattering, spontaneous parametric down conversion, and spontaneous four-wave mixing. TMs can be manipulated, converted, demultiplexed, and detected using nonlinear optical processes such as three-wave mixing and quantum optical memories. As such, they play an increasingly important role in constructing quantum information networks.
Jawad Mirza et al 2024 Phys. Scr. 99 055513
The spectrum required for future optical communication systems is being extended towards the C-, L- and U-bands, resulting in a significant interest in the spectral region around 2 μm wavelength. Since Holmium doped fiber amplifiers (HDFAs) provide amplification in this spectral region, they have become a focus of researchers working on doped fiber amplifiers. A major factor resulting in the performance degradation of HDFAs is the inhomogeneous energy transfer within Ho3+ ion-pairs in high-concentration Holmium-doped fibers (HDFs), an effect generally known as pair-induced quenching (PIQ). In this paper, we study the luminal and temporal dynamics of pulses of different repetition rates at 2.05 μm in high-concentration HDFs considering the effects of ion-pairs. Input pulses having repetition rates of 25 GHz and 500 kHz are generated using wavelength tunable actively mode-locked Holmium-doped fiber laser (AML-HDFL) based on a single ring cavity and bidirectional pumping. The characteristics of the pulses propagating through high-concentration HDF are analyzed based on different metrics such as average power, peak power, pulse energy, full-width at half maximum (FWHM), and time delay without and with ion-pairs for values of fraction of ion-pairs k = 0 and k = 10%, respectively. The results obtained at optimized length of HDF show that ion-pairs significantly degrade the average power, peak power, and energy of the output pulses for both of the repetition rates. For both k = 0 and k = 10%, the FWHM and shape of the output pulses remain same in the presence of the ion-pairs while, time delay of 4 ps and 19 ns is observed in the output pulses at repetition rates of 25 GHz and 500 kHz, respectively. The effects of increasing the pump and signal power on the average power and energy of the output pulses for k = 0 and k = 10% are also discussed for both repetition rates. This analysis provides important guidelines for designers of 2 μm fiber lasers and amplifiers based on high-concentration HDFs.
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A Davlatov et al 2024 Phys. Scr. 99 075933
In this research, electron energy levels were calculated analytically using Nelson's formula, the shooting method, and Garrett's formula for effective mass. These calculations were performed for a rectangular finite deep potential well, focusing on the InP/InAs/InP heterostructure, which is a narrow-bandgap semiconductor system. Our results demonstrate that the nonparabolicity of the dispersion has a more significant effect on higher energy levels compared to lower ones, with deviations of up to 15% for the third energy level. An equation estimating the number of observable energy levels in the potential well is suggested, revealing that considering nonparabolicity leads to a 20% increase in the number of levels compared to the parabolic dispersion case. The relationship between the widths of infinite and finite potential wells for equivalent energy levels follows a linear behaviour, with bonding coefficients ranging from 95,93% to 97,49% and a maximum difference of 1.5% between parabolic and non-parabolic cases. The transcendental equation for the energy levels is linearized, yielding a fourth-order equation that provides results within 98% accuracy compared to the original equation. These findings contribute to the understanding of the energy distribution in InP/InAs/InP heterostructures with a view to their application in optoelectronic devices such as lasers, light-emitting diodes
Anuj Kumar et al 2024 Phys. Scr. 99 075927
Due to its ideal optical and electrical properties for upcoming electronic devices, Cu2O is commonly regarded as one of the most promising p-type oxides. Copper (Cu) rapidly deposits mixed phases of its oxides. This article describes the spray deposition method for developing copper oxide thin films at temperatures between 200 and 400 °C on glass substrates coated with ITO. Through optimization of the deposition temperature, Cu2O-rich phases were attained in the copper oxide films, typically around 300 °C. A Cu-rich phase was seen at 200 °C deposition temperature, and this phase progressively diminished at higher temperatures. At 400 °C, the CuO phase began to enrich the films in the meantime. Analysis using an x-ray diffraction (XRD) verified the existence of Cu2O phases (111), (200), and (220). The crystallites were discovered to be between 17.49 and 20.32 nm in size for the films deposited between 300 and 400 °C. The x-ray Photoelectron Spectroscopy (XPS) identifies Cu and oxygen as the main components. Furthermore, it is demonstrated that the deposition temperature significantly affects the copper's oxidation state. The Atomic Force Microscopy (AFM) investigation showed that as the temperature increased, surface roughness decreased. As the deposition temperature increased, the energy band gap of the deposited films widened from 1.67 to 2.85 eV, as observed by the UV–vis-NIR spectrophotometer. Moreover, the fabrication of Schottky diodes with Cu metal contacts is also reported. These fabricated diodes showed a proportionate rise in barrier height with increasing deposition temperature.
F Bedrouni et al 2024 Phys. Scr. 99 075919
In this paper, atmospheric pressure plasma of ambient air was generated by a surface dielectric barrier discharge (SDBD) device for the purpose of modifying the surface of isotactic-polypropylene (iPP). The effect of SDBD treatment time on the chemical and physical properties of iPP was studied using various analytical techniques including, water contact angle (WCA), attenuated total reflection (ATR), Raman spectroscopy, x-ray diffraction (XRD), and atomic force microscopy (AFM). The results indicate that the hydrophilicity and the C=O bonds of the treated iPP were improved as observed, respectively, through WCA and ATR analysis. The crystal structure was evaluated by Raman spectroscopy and XRD. It was found that the iPP chain was under microscopic stress, which affected its crystallinity degree depending on the duration of the treatment. Furthermore, the AFM analysis revealed that the surface roughness was substantially modified.
Junchang Yu et al 2024 Phys. Scr. 99 075304
In radiation dosimetry and medical dosimetry, optical fiber dosimeters have great advantages in application due to their small size and long transmission distance. However, in some low-dose radiation environments, the water inequivalence error and angle error of optical fiber dosimeters can have significant impacts that cannot be ignored. In this paper, the effects of ray energy, ray solid angle and optical fiber probe size on water inequivalence error and angle error are analyzed by using Monte Carlo simulation. Due to the complexity of the influencing factors of the angle error, which is difficult to be analyzed precisely and quantitatively, a correction method based on BP neural network is proposed. The final validation results demonstrate that the correction scheme can reduce the total angle error of the optical fiber dosimeter to
Enze Wang et al 2024 Phys. Scr. 99 075926
Magnetron sputtering is an alternative approach to prepare flexible copper clad laminates because of low cost and thin copper clad laminate thickness. However, Cu film has poor adhesion when directly deposited on polymer substrates, imposing certain limits to the use of magnetron sputtering technique. This work aims to improve the adhesion between the copper film and the polymer substrate. In this work, we succeeded improved the adhesion between the polymer substrates and copper film by introducing different metal interlayers into the polymer/Cu interfaces. It was found that the the copper films with Ni interlayer have the best adhesion with polymer substrates. This study proposes a promising route to overcome the wear adhesion problem between Cu film and polymers in the preparation of magnetron sputtered flexible copper clad laminates.
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Da Zhang et al 2024 Phys. Scr. 99 062010
The arc discharge plasma (ADP) technology has been widely developed in the fields of cutting, welding, spraying and nanomaterials synthesis over the past 20 years. However, during the process of ADP, it is difficult to explain the generation and evolution of arc column, the interaction between arc column and electrodes, as well as the effect of plasma generator structure on the physical characteristics of ADP by experimental means. Therefore, numerical simulation has become an effective mean to explore the physical characteristics of ADP, but also faces severe challenges because it involves multiple physical field coupling, resolution of multiscale features as well as robustness in the presence of large gradients. From the point of view of the construction of ADP mathematical physical models and combined with the practical application of ADP, this paper systematically reviews the researches on physical properties of arc column, near-cathode region, near-anode region as well as the today's state of the numerical simulation of plasma generators. It provides a good reference for further mastering the physical characteristics of plasma, guiding the industrial application of plasma and optimizing the design of plasma generators. Meanwhile, the relevant computational aspects are discussed and the challenges of plasma numerical simulation in the future are summarized.
Muhammad Usman et al 2024 Phys. Scr. 99 062009
Infectious diseases caused by bacterial pathogens are currently a significant problem for global public health. Rapid diagnosis and effective treatment of clinically significant bacterial pathogens can prevent, control, and inhibit infectious diseases. Therefore, there is an urgent need to develop selective and accurate diagnostic methods for bacterial pathogens and clinically effective treatment strategies for infectious diseases. In recent years, developing novel nanoparticles has dramatically facilitated the rapid and accurate diagnosis of bacterial pathogens and the precise treatment of contagious diseases. In this review, we systematically investigated a variety of nanoparticles currently applied in the diagnosis and treatment of bacterial pathogens, from synthesis procedures to structural characterization and then to biological functions. In particular, we first discussed the current progress in applying representative nanoparticles for bacterial pathogen diagnostics. The potential nanoparticle-based treatment for the control of bacterial infections was then carefully explored. We also discussed nanoparticles as a drug delivery method for reducing antibiotic global adverse effects and eradicating bacterial biofilm formation. Furthermore, we studied the highly effective nanoparticles for therapeutic applications in terms of safety issues. Finally, a concise and insightful discussion of nanoparticles' limitations, challenges, and perspectives for diagnosing and eradicating bacterial pathogens in clinical settings was conducted to provide a direction for future development.
M E Semenov et al 2024 Phys. Scr. 99 062008
The Preisach model is a well-known model of hysteresis in the modern nonlinear science. This paper provides an overview of works that are focusing on the study of dynamical systems from various areas (physics, economics, biology), where the Preisach model plays a key role in the formalization of hysteresis dependencies. Here we describe the input-output relations of the classical Preisach operator, its basic properties, methods of constructing the output using the demagnetization function formalism, a generalization of the classical Preisach operator for the case of vector input-output relations. Various generalizations of the model are described here in relation to systems containing ferromagnetic and ferroelectric materials. The main attention we pay to experimental works, where the Preisach model has been used for analytic description of the experimentally observed results. Also, we describe a wide range of the technical applications of the Preisach model in such fields as energy storage devices, systems under piezoelectric effect, models of systems with long-term memory. The properties of the Preisach operator in terms of reaction to stochastic external impacts are described and a generalization of the model for the case of the stochastic threshold numbers of its elementary components is given.
A Srinivasa Rao 2024 Phys. Scr. 99 062007
Over the past 36 years much research has been carried out on Bessel beams (BBs) owing to their peculiar properties, viz non-diffraction behavior, self-healing nature, possession of well-defined orbital angular momentum with helical wave-front, and realization of smallest central lobe. Here, we provide a detailed review on BBs from their inception to recent developments. We outline the fundamental concepts involved in the origin of the BB. The theoretical foundation of these beams was described and then their experimental realization through different techniques was explored. We provide an elaborate discussion on the different kinds of structured modes produced by the BB. The advantages and challenges that come with the generation and applications of the BB are discussed with examples. This review provides reference material for readers who wish to work with non-diffracting modes and promotes the application of such modes in interdisciplinary research areas.
Amrinder Mehta et al 2024 Phys. Scr. 99 062006
Shape Memory Alloys (SMAs) are metallic materials with unique thermomechanical characteristics that can regain their original shape after deformation. SMAs have been used in a range of industries. These include consumer electronics, touch devices, automobile parts, aircraft parts, and biomedical equipment. In this work, we define the current state of the art in SMA manufacturing and distribution across the aerospace, healthcare, and aerospace industries. We examine the effect of manganese on the structure and mechanical and corrosive properties of SMA Cu-Al-Ni and discuss the importance of incorporating small and medium-sized enterprises in the study of cu-Al luminum. This research outlines a fundamental example of SME integration in the analysis of superelasticity, a critical instance of SMA activity. It can also serve as a reference for activities such as medical, aerospace, and other industries that target SMA-based equipment and systems. Also, they can be used to look at SMA activation and material upgrade mechanisms. These FEM simulations are advantageous in optimizing and promoting design in fields such as aerospace and healthcare. FEM simulations identify the stress and strength of SMA-based devices and structures. This would result in minimizing cost and usage and lowering the risk of damage. FEM simulations can also recognize the weaknesses of the SMA designs and suggest improvements or adjustments to SMA-based designs.
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Dong et al
Arcing is widely used in the processing and manufacturing of electrical materials. Arc duration and stability play a key role in the quality and efficiency of arc welding and cutting. Additionally, the generation of the arc will cause faults, failures, and even fire, and explosion in the electrical contact system. Arc is also a critical problem that threatens the safe and stable work of electrical contact systems. Therefore, a platform for arc experiment and test analysis in a multi-atmosphere environment is built in this paper. The influence of the gas environments and gas pressures on arc breaking distance and ablation characteristics is explored. The experimental results show that the oxygen environment is conducive to rapid arc extinguishing. This phenomenon is because oxygen has strong electronegativity, which makes it easy to adsorb charged particles and leads to a density decrease of charged particles. The variation of arc breaking distance and ablation characteristics under different gas environments and gas pressures is found. The influence mechanism of gas environments and gas pressures on arc breaking distance and ablation characteristics are explored. The correlation mechanism between arc breaking distance and arc ablation characteristics is revealed. The research results provide theoretical support for improving the quality of electrical material processing and manufacturing and the service life of electric contact systems. Keywords: Arc breaking distance, arc stability, arc ablation, different arcing environments
Yang et al
A refined nonlocal zigzag model for thermal buckling analysis of nano composite laminated and sandwich beams is proposed in this study based on a refined zigzag theory and Eringen's nonlocal theory. Firstly, present model satisfies the stress-free and continuity conditions a priori by introducing the piecewise-linear zigzag functions and a preprocessing, such that the transverse shear correction factors are not needed. In the preprocessing, accurate and continuous transverse shear stresses are obtained with the aid of the general mixed variational principle, which can be solved simultaneously with other stresses in the governing equations. This is quite different from the previous post-processing. Subsequently, thermal buckling problems of nano composite laminated and sandwich beams are analytically solved in simply supported boundary conditions. The degenerated results without small effect indicate that the non-dimensional critical loads and critical temperatures have a good agreement with the 3D elasticity solutions and previous results, which demonstrate the accuracy and reliability of present model. Moreover, it is observed that the small effect of the critical temperatures can be effectively captured by Eringen's differential constitutive law (EDCL), which shows the small effect decreases the critical temperature by weakening the stiffness of the beam. Finally, the effects of different thermal expansion coefficients, laminations, geometric sizes and beam theories are discussed. The results show that present model is robust in the arbitrary layouts for both of composite and sandwich structures, which may have some referential significance to Micro-Electro-Mechanical Systems (MEMS) sensors and actuators.
Abu El Maaty et al
Energy levels, lifetimes, oscillator strengths and transition probabilities for the multicharged carbon like K XIV ion have been calculated with the configuration expansion: 2s$^2$2p$^2$, 2p$^4$, 2s$^2$2p3p, 2s$^2$2p4p, 2s2p$^2$3s, 2s2p$^2$4s, 2s2p$^2$3d, 2s2p$^2$4d, 2s2p$^2$3p, 2s2p$^2$4p, 2s$^2$2p3s, 2s$^2$2p4s, 2s$^2$2p3d, 2s$^2$2p4d and 2s2p$^3$. Two methods were used in the calculations: the Hartree-Fock pseudo-relativistic approach and the Thomas-Fermi-Dirac-Amaldi potential approach using the Cowan and the AUTOSTRUCTURE atomic structure codes respectively. Results have been compared with data from National Institute of Standards and Technology Atomic Spectra Database (NIST-ASD) and from other theoretical methods. Obtained new data will be important for plasma analysis in laboratories and for astrophysical modeling.
Kim et al
The ropelength of a knotted string with volume is defined as the ratio of the length of its central curve to the radius of its sectional disc. In a physical context, achieving minimal ropelength corresponds to a state of minimal potential energy, and geometrically, it signifies a tightly-packed conformation. The quest to establish a connection be- tween the topological complexity of knotted strings and their minimal ropelength has persisted into recent years. In this paper, we introduce a new upper bound on the minimal ropelength of (2, n)-torus knots and links: Rop(T (2, n)) ≤ 7.3163 Cr(T (2, n)) + 17.1657. This upper bound is derived from a torus knot conformation constructed based on a tight- ened pattern of double helix with non-identical radii of winding. A comparative analysis with conformations generated from a superhelix and a circular helix underscores the efficiency of the non-identical dou- ble helix pattern, particularly when it appears as a long repeated motif in knotted strings.
abdelhakim et al
This paper investigates the influence of the extended uncertainty principle (EUP) and non-linearity on Bose-Einstein condensate (BEC) confined within an infinite potential well, described by a deformed one-dimensional Gross-Pitaevskii equation (GPE). Exact solutions are derived, and the impact of the EUP and the parameter of interaction g is explored through solution, position and momentum uncertainties plots. The study reveals significant changes in the probability density and energy spectra, depending on the deformation and non-linearity parameters.
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George Biswas et al 2024 Phys. Scr. 99 075103
We investigate the fidelity of Haar random bipartite pure states from a fixed reference quantum state and their bipartite entanglement. By plotting the fidelity and entanglement on perpendicular axes, we observe that the resulting plots exhibit non-uniform distributions. The distribution depends on the entanglement of the fixed reference quantum state used to quantify the fidelity of the random pure bipartite states. We find that the average fidelity of typical random pure bipartite qubits within a narrow entanglement range with respect to a randomly chosen fixed bipartite qubit is . Extending our study to higher dimensional bipartite qudits, we find that the average fidelity of typical random pure bipartite qudits with respect to a randomly chosen fixed bipartite qudit remains constant within a narrow entanglement range. The values of these constants are , with d being the dimension of the local Hilbert space of the bipartite qudit system, suggesting a consistent relationship between entanglement and fidelity across different dimensions. The probability distribution functions of fidelity with respect to a product state are analytically studied and used as a reference for the benchmarking of distributed quantum computing devices.
Sheng Liu et al 2024 Phys. Scr. 99 075604
Based on the parameters of the HL-2A experiment, the effect of energetic particles (EPs) on non-resonant high-order harmonics energetic particle modes (EPMs) with qmin>1 is investigated in the present work. Hybrid kinetic-magnetohydrodynamic nonlinear code M3D-K is performed to simulate the linear properties and the nonlinear evolution of the non-resonant EPM during neutral beam injection (NBI). To deeply understand the physical mechanism of interaction resonant between energetic-ions and non-resonant EPM, this work compares the effects of passing energetic particles and trapped energetic particles on the non-resonant EPM instabilities. It is numerically identified that EPs' effects on high n harmonics (m/n = 2/2, 3/3, 4/4) instability are more obvious than the m/n = 1/1 mode. Furthermore, the effects of energetic particles injection energy, the minimum safety factor qmin , toroidal rotation and beam ion distribution on the features of high n harmonics are also investigated specifically. Toroidal rotation is found to suppress high n harmonics, which is more obvious for the modes driven by trapped particles. Nonlinear simulation results show that these non-resonant high n harmonics can induce larger energetic ion transport, which may affect the plasma confinement performance.
Srihari N V et al 2024 Phys. Scr. 99 075917
Bismuth ferrite (BFO) is a prime candidate for room-temperature magnetoelectric coupling and multiferroic applications. The rhombohedral R3c phase of BFO is the source of many properties, but the phase purity and oxygen vacancies are still the biggest obstacles to its real-world application. Considering these facts, the present work investigates the effects of oxygen vacancies on the functional properties through manipulation of drying temperatures of spin-cast films, especially at temperatures around 280 °C, where both the secondary phase and oxygen vacancies are prevalent. One of the biggest sources of oxygen vacancy is bismuth volatilisation, and our work deals with the situation head-on, uncovering the effect of bismuth volatilisation on functional properties. The structural properties were studied using x-ray diffraction (XRD), and deeper insights into the surface topography of the samples were obtained using AFM imaging. The electrical and dielectric characteristics help distinguish and analyse the samples in terms of the presence of resistive switching. PUND studies were performed to determine the ferroelectric properties of the samples. A fifty percent reduction in the oxygen vacancies in the presence of secondary phases was observed when compared with the phase-pure sample, as shown by the XPS analysis. Deeper insights were provided into the valence band spectra by first-principles studies. This work shows that phase purity may not be the singular condition for enhancing functional properties, and fine-tuning the presence of secondary phases and oxygen vacancies may be the way forward. The ferroelectric polarisation in one of the samples exhibits a notably higher value when using chemical solution deposition methods, making it a promising candidate for memory devices.
Chongbin Xi et al 2024 Phys. Scr. 99 075513
In order to reduce the requirement of system bandwidth of Laser Doppler Velocimeter (LDV), a Dual-Doppler signal mixing LDV is proposed in this paper. By transmitting two beams to the moving surface, two Doppler signals are acquired and subsequently mixed to obtain a difference frequency signal. The measured speed can be calculated based on the frequency of this difference frequency signal. This novel structure significantly reduces the bandwidth requirements on the system, which can be further diminished by minimizing the angle between the two beams of the emitted light. Moreover, it exhibits enhanced robustness against variations in launch angle and enables defocusing measurements.
Sayed S.R Moustafa and Sara Said Khodairy 2024 Phys. Scr.
This investigation presents a comprehensive analysis of the historical trajectory of sunspot number (SSN) observations in Egypt, a country renowned for its rich astronomical heritage. Despite Egypt's long-standing practice in solar observation, the local SSN datasets are marred by a significant incidence of missing entries, posing formidable obstacles to the accurate evaluation of solar activity. Addressing this challenge, the study employs dynamic time warping (DTW) as a methodological tool to assess the alignment of local and global SSN datasets. This technique adeptly harmonizes these datasets by reconciling temporal inconsistencies and variations in sampling rates. Subsequent to the application of DTW, the research integrates orthogonal regression for the imputation of the absent values in the Egyptian SSN dataset. This method, preferred for its proficiency in managing errors in both the dependent and independent variables, deviates from conventional linear regression techniques, thereby providing a more nuanced approach to data approximation. The analysis unveils a substantial correlation between the estimated local SSN values and the global SSN indices, with the former consistently exhibiting lower figures. Nevertheless, these local values display parallel trends and seasonal fluctuations akin to those observed in the global dataset, validating the imputation method and highlighting the unique characteristics of the Egyptian SSN data within the global context of solar activity monitoring. The implications of these findings are significant for the discipline of solar physics, especially for regions contending with incomplete datasets. The methodologies advanced in this research offer a robust framework for the enhancement of datasets with missing data, thus broadening the comprehension of solar phenomena.
G Lopardo et al 2024 Phys. Scr. 99 075912
A new cryostat for the realization of the triple-point of the argon (83.8058 K), a defining fixed point of the International Temperature Scale of 1990 (ITS-90), was acquired at Italian National Metrological Institute (INRiM). The new system, manufactured by Fluke, is intended to substitute the current National reference, a model developed at BNM-INM in the 1975. The main difference between the two system is in the way to control the temperature. In the BNM-INM device the temperature is controlled adjusting the pressure of liquid nitrogen bath, in the Fluke system instead, an electrical heater wrapped around the argon cell is used, following cryogenic practice. This paper describes the result of the direct comparison and shows typical phase transitions obtained with the two argon systems. Then, a complete uncertainty budget is evaluated for the new Fluke system and compared with the National standard.
Axel Schulze-Halberg 2024 Phys. Scr. 99 075212
We construct approximate solutions to the stationary, one-dimensional Schrödinger equation for a hyperbolic double-well potential within the Dunkl formalism. Our approximation is applied to an inverse quadratic term contributed by the Dunkl formalism in the effective potential. The solutions we obtain are given in terms of confluent Heun functions. We establish parity of these solutions, discuss their elementary cases, and present an example of a system admitting bound states.
Mingzhu Li et al 2024 Phys. Scr.
Photons can freely propagate in the vacuum state, so the vacuum is not a trivial insulator, but a conductor for photons. Because of this reason, in topological photonics, the domain wall structures with opposite effective mass terms as a cladding to confine electromagnetic waves have to be adopted to demonstrate the topological edge/surface waves and Fermi arc surface states. In this work, based on the ideal Weyl gyromagnetic metamaterials (GMs), we demonstrate that can be realized the cladding-free Fermi arc surface states with high field localization on the boundary. In the GMs, the ideal Weyl semimetal phase exists due to the dispersionless longitudinal modes. The claddingfree Fermi arc surface states connect the projections of the Weyl points with opposite chirality at the boundary owing to the bulk-edge correspondence of the vacuum-GMs system. Full-wave simulations further demonstrate that that chiral surface waves can seamlessly propagate forward around various types of defects without experiencing scattering or backward reflection. Remarkably, different types of topological directional couplers are achieved by utilizing the cladding-free Fermi arc surface states in the ideal GMs. We theoretically demonstrate that the physical mechanism of realizing the topological directional couplers is caused by the single coupling channel between the cladding-free Fermi arc surface states and scatterers of the vacuum-GMs system. Moreover, the controllable propagation and topological directional coupling of the cladding-free Fermi arc surface states can be realized by changing the gyromagnetic parameters and boundary configurations in the topological directional couplers. Our work could provide more flexibility for the cladding-free and directional coupling topological devices.
Anh-Luan Phan et al 2024 Phys. Scr. 99 075903
We analyze and present applications of a recently proposed empirical tight-binding scheme for investigating the effects of alloy disorder on various electronic and optical properties of semiconductor alloys, such as the band gap variation, the localization of charge carriers, and the optical transitions. The results for a typical antimony-containing III-V alloy, GaAsSb, show that the new scheme greatly improves the accuracy in reproducing the experimental alloy band gaps compared to other widely used schemes. The atomistic nature of the empirical tight-binding approach paired with a reliable parameterization enables more detailed physical insights into the effects of disorder in alloyed materials.
Johannes K Krondorfer et al 2024 Phys. Scr.
Optical nuclear electric resonance (ONER), a recently proposed protocol for nuclear spin manipulation in atomic systems via short laser pulses with MHz repetition rate, exploits the coupling between the nuclear quadrupole moment of a suitable atom and the periodic modulations of the electric field gradient generated by an optically stimulated electronic excitation. In this theory paper, we extend the scope of ONER from atomic to molecular systems and show that molecular vibrations do not interfere with our protocol. Exploring the diatomic molecule LiNa as a first benchmark system, our investigation showcases the robustness with respect to molecular vibration, and the ability to address and manipulate each of the two nuclear spins independently, simply by adjusting the repetition rate of a pulsed laser. Our findings suggest that it might be possible to shift complicated spin manipulation tasks required for quantum computing into the time domain by pulse-duration encoded laser signals.