{"title":"Quantum Gravity Gets a New Test","authors":"Ryan Wilkinson","doi":"10.1103/physics.17.65","DOIUrl":"https://doi.org/10.1103/physics.17.65","url":null,"abstract":"","PeriodicalId":20136,"journal":{"name":"Physics","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141031666","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper, we study the influence of a small group of agents (i.e., a lobby) that is trying to spread a rumor in a population by using the known model proposed by Serge Galam. In particular, lobbies are modeled as subgroups of individuals who strategically choose their seating in the social space in order to protect their opinions and influence others. We consider different social gatherings and simulate, using finite Markovian chains, opinion dynamics by comparing situations with a lobby to those without a lobby. Our results show how the lobby can influence opinion dynamics in terms of the prevailing opinion and the mean time to reach unanimity. The approach that we take overcomes some of the problems that behavioral economics and psychology have recently struggled with in terms of replicability. This approach is related to the methodological revolution that is slowly changing the dominant perspective in psychology.
{"title":"The Influence of Lobbies: Analyzing Group Consensus from a Physics Approach","authors":"U. Merlone, Arianna Dal Forno","doi":"10.3390/physics6020043","DOIUrl":"https://doi.org/10.3390/physics6020043","url":null,"abstract":"In this paper, we study the influence of a small group of agents (i.e., a lobby) that is trying to spread a rumor in a population by using the known model proposed by Serge Galam. In particular, lobbies are modeled as subgroups of individuals who strategically choose their seating in the social space in order to protect their opinions and influence others. We consider different social gatherings and simulate, using finite Markovian chains, opinion dynamics by comparing situations with a lobby to those without a lobby. Our results show how the lobby can influence opinion dynamics in terms of the prevailing opinion and the mean time to reach unanimity. The approach that we take overcomes some of the problems that behavioral economics and psychology have recently struggled with in terms of replicability. This approach is related to the methodological revolution that is slowly changing the dominant perspective in psychology.","PeriodicalId":20136,"journal":{"name":"Physics","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141029651","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Since the middle of the 20th century, an understanding of the diversity of the natural magnetohydrodynamic phenomena surrounding us has begun to emerge. Magnetohydrodynamic nature manifests itself in such seemingly heterogeneous processes as the flow of water in the world’s oceans, the movements of Earth’s liquid core, the dynamics of the solar magnetosphere and galactic electromagnetic fields. Their close relationship and multifaceted influence on human life are becoming more and more clearly revealed. The study of these phenomena requires the development of theory both fundamental and analytical, unifying a wide range of phenomena, and specialized areas that describe specific processes. The theory of translational fluid motion is well developed, but for most natural phenomena, this condition leads to a rather limited model. The fluid motion in the cavity of a rotating body such that the Coriolis forces are significant has been studied much less. A distinctive feature of the problems under consideration is their significant nonlinearity, (i.e., the absence of a linear approximation that allows one to obtain nontrivial useful results). From this point of view, the studies presented here were selected. This review presents studies on the movements of ideal and viscous fluids without taking into account electromagnetic phenomena (non-conducting, non-magnetic fluid) and while taking them into account (conducting fluid). Much attention is payed to the macroscopic movements of sea water (conducting liquid) located in Earth’s magnetic field, which spawns electric currents and, as a result, an induced magnetic field. Exploring the processes of generating magnetic fields in the moving turbulent flows of conducting fluid in the frame of dynamic systems with distributed parameters allows better understanding of the origin of cosmic magnetic fields (those of planets, stars, and galaxies). Various approaches are presented for rotational and librational movements. In particular, an analytical solution of three-dimensional unsteady magnetohydrodynamic equations for problems in a plane-parallel configuration is presented.
{"title":"Dynamics of Fluids in the Cavity of a Rotating Body: A Review of Analytical Solutions","authors":"A. A. Gurchenkov, Ivan A. Matveev","doi":"10.3390/physics6010029","DOIUrl":"https://doi.org/10.3390/physics6010029","url":null,"abstract":"Since the middle of the 20th century, an understanding of the diversity of the natural magnetohydrodynamic phenomena surrounding us has begun to emerge. Magnetohydrodynamic nature manifests itself in such seemingly heterogeneous processes as the flow of water in the world’s oceans, the movements of Earth’s liquid core, the dynamics of the solar magnetosphere and galactic electromagnetic fields. Their close relationship and multifaceted influence on human life are becoming more and more clearly revealed. The study of these phenomena requires the development of theory both fundamental and analytical, unifying a wide range of phenomena, and specialized areas that describe specific processes. The theory of translational fluid motion is well developed, but for most natural phenomena, this condition leads to a rather limited model. The fluid motion in the cavity of a rotating body such that the Coriolis forces are significant has been studied much less. A distinctive feature of the problems under consideration is their significant nonlinearity, (i.e., the absence of a linear approximation that allows one to obtain nontrivial useful results). From this point of view, the studies presented here were selected. This review presents studies on the movements of ideal and viscous fluids without taking into account electromagnetic phenomena (non-conducting, non-magnetic fluid) and while taking them into account (conducting fluid). Much attention is payed to the macroscopic movements of sea water (conducting liquid) located in Earth’s magnetic field, which spawns electric currents and, as a result, an induced magnetic field. Exploring the processes of generating magnetic fields in the moving turbulent flows of conducting fluid in the frame of dynamic systems with distributed parameters allows better understanding of the origin of cosmic magnetic fields (those of planets, stars, and galaxies). Various approaches are presented for rotational and librational movements. In particular, an analytical solution of three-dimensional unsteady magnetohydrodynamic equations for problems in a plane-parallel configuration is presented.","PeriodicalId":20136,"journal":{"name":"Physics","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2024-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140230256","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Matthew J. Gorban, William D. Julius, Patrick M. Brown, Jacob A. Matulevich, Gerald B. Cleaver
There was an error in the original paper [1], which occurred in the calculation of the DCE spectrum from the time-dependant perturbations on λ(t) [...]
原论文[1]中的一个错误发生在根据λ(t)上的时变扰动计算 DCE 频谱的过程中[......]
{"title":"Correction: Gorban et al. The Asymmetric Dynamical Casimir Effect. Physics 2023, 5, 398–422","authors":"Matthew J. Gorban, William D. Julius, Patrick M. Brown, Jacob A. Matulevich, Gerald B. Cleaver","doi":"10.3390/physics6010028","DOIUrl":"https://doi.org/10.3390/physics6010028","url":null,"abstract":"There was an error in the original paper [1], which occurred in the calculation of the DCE spectrum from the time-dependant perturbations on λ(t) [...]","PeriodicalId":20136,"journal":{"name":"Physics","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2024-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140241565","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. G. Castillo-López, R. Esquivel-Sirvent, G. Pirruccio, Carlos Villarreal
We investigate the influence of the Abrikosov vortex lattice on the Casimir force in a setup constituted by high-temperature superconductors subject to an external magnetic field. The Abrikosov lattice is a property of type II superconductors in which normal and superconducting carriers coexist and the latter define a periodic pattern with square symmetry. We find that the optical properties determined by spatial redistribution of the superconducting order parameter induce Casimir forces with a periodic structure whose minimal strengths coincide with the vortex cores.
我们研究了在由高温超导体构成的装置中，阿布里科索夫涡流晶格对外部磁场的卡西米尔力的影响。阿布里科索夫晶格是 II 型超导体的一种特性，其中正常载流子和超导载流子共存，后者定义了一种具有正方形对称性的周期性图案。我们发现，由超导有序参数的空间再分布决定的光学特性会诱发具有周期性结构的卡西米尔力，其最小强度与涡旋核心相吻合。
{"title":"Casimir Forces with Periodic Structures: Abrikosov Flux Lattices","authors":"S. G. Castillo-López, R. Esquivel-Sirvent, G. Pirruccio, Carlos Villarreal","doi":"10.3390/physics6010026","DOIUrl":"https://doi.org/10.3390/physics6010026","url":null,"abstract":"We investigate the influence of the Abrikosov vortex lattice on the Casimir force in a setup constituted by high-temperature superconductors subject to an external magnetic field. The Abrikosov lattice is a property of type II superconductors in which normal and superconducting carriers coexist and the latter define a periodic pattern with square symmetry. We find that the optical properties determined by spatial redistribution of the superconducting order parameter induce Casimir forces with a periodic structure whose minimal strengths coincide with the vortex cores.","PeriodicalId":20136,"journal":{"name":"Physics","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2024-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140251455","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Contributions to the radiation-induced dispersion energy shift between two interacting particles dependent on the electric octupole moment are calculated using a physical picture in which moments induced by applied fluctuating electromagnetic fields are coupled via retarded interaction tensors. The specific potentials evaluated include those found between an electric dipole-polarisable molecule and either a mixed electric dipole–octupole- or purely octupole-polarisable molecule, and those between two mixed electric dipole–octupole-polarisable molecules. Interaction energies are obtained for molecular and pair orientationally averaged situations. Terms dependent on the octupole weight-1 moment may be viewed as higher-order corrections to the leading dipole–dipole interaction energy as also found in energy transfer and dispersion forces. A comprehensive polarisation analysis is carried out for linearly and circularly polarised laser light incident parallel and perpendicular to the inter-particle axis. Contributions to the optical binding energy arising when one of the pair is polar and characterised by either a permanent electric dipole or octupole moment are also evaluated. Neither of these energy shifts survive orientational averaging.
{"title":"Electric Octupole-Dependent Contributions to Optical Binding Energy","authors":"A. Salam","doi":"10.3390/physics6010025","DOIUrl":"https://doi.org/10.3390/physics6010025","url":null,"abstract":"Contributions to the radiation-induced dispersion energy shift between two interacting particles dependent on the electric octupole moment are calculated using a physical picture in which moments induced by applied fluctuating electromagnetic fields are coupled via retarded interaction tensors. The specific potentials evaluated include those found between an electric dipole-polarisable molecule and either a mixed electric dipole–octupole- or purely octupole-polarisable molecule, and those between two mixed electric dipole–octupole-polarisable molecules. Interaction energies are obtained for molecular and pair orientationally averaged situations. Terms dependent on the octupole weight-1 moment may be viewed as higher-order corrections to the leading dipole–dipole interaction energy as also found in energy transfer and dispersion forces. A comprehensive polarisation analysis is carried out for linearly and circularly polarised laser light incident parallel and perpendicular to the inter-particle axis. Contributions to the optical binding energy arising when one of the pair is polar and characterised by either a permanent electric dipole or octupole moment are also evaluated. Neither of these energy shifts survive orientational averaging.","PeriodicalId":20136,"journal":{"name":"Physics","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2024-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140261543","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The interaction of the 238U with a neutron is studied. Correct accounting for the non-spherical shape of the uranium nucleus is in focus. The optical potential is used as a model. It is shown that the spherically symmetric and non-spherical potentials give different scattering patterns, in particular different resonance features of the cross-section. The possibility of using the method as an extension of the particle–rotor model of the nucleus is illustrated.
{"title":"Three-Dimension Calculation for the Scattering Problem for Non-Spherical Potential","authors":"P. Krassovitskiy, Fedor M. Pen’kov","doi":"10.3390/physics6010024","DOIUrl":"https://doi.org/10.3390/physics6010024","url":null,"abstract":"The interaction of the 238U with a neutron is studied. Correct accounting for the non-spherical shape of the uranium nucleus is in focus. The optical potential is used as a model. It is shown that the spherically symmetric and non-spherical potentials give different scattering patterns, in particular different resonance features of the cross-section. The possibility of using the method as an extension of the particle–rotor model of the nucleus is illustrated.","PeriodicalId":20136,"journal":{"name":"Physics","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2024-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140262245","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study deals with the preparation of magnetite nanoparticles (NPs) via a coprecipitation method using several precipitation bases: binary precipitator (NH4OH), mono precipitator (NaOH), and weak precipitator (Ca(OH)2). The prepared magnetite NPs were identified using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis, surface area analysis, magnetic properties, Fourier-transformed infrared spectra (FT-IR), and ultra-violet UV–visible spectra. As a result, the phases of the produced magnetite NPs were unaffected by the use of various bases, but their crystallite sizes were affected. It was found that the binary base provided the smallest crystallite size, the mono base provided an average size, and the weak base provided the largest crystallite size. The UV–visible absorption spectroscopy investigation revealed that the absorption and the energy gap rose with a reduction in nanoparticle size. The prepared magnetite NPs were used to manufacture polymeric-based nanocomposites employed as protective shields from low-energy X-rays that are light in weight. These samples were identified using XRD, atomic force microscopy (AFM), and FT-IR spectroscopy. The crystallite size was slightly larger than it was in the case of magnetite NPs. This is consistent with the results of AFM. The interference between the two phases was observed in the results of the FT-IR spectra. The effects of the size of the magnetite NPs on the attenuation tests, linear attenuation coefficient, mass attenuation coefficient, half-value layer, and mean free path were investigated. The results showed that the efficiency of using manufactured shields increases with the decrease in the NPs size of the magnetite used as a reinforcement phase for a range of low operating voltages.
本研究通过共沉淀法制备磁铁矿纳米颗粒（NPs），使用了几种沉淀碱：二元沉淀剂（NH4OH）、一元沉淀剂（NaOH）和弱沉淀剂（Ca(OH)2）。利用 X 射线衍射 (XRD)、透射电子显微镜 (TEM)、扫描电子显微镜 (SEM)、能量色散 X 射线 (EDX) 分析、表面积分析、磁性能、傅立叶变换红外光谱 (FT-IR) 和紫外可见光谱对制备的磁铁矿 NPs 进行了鉴定。结果表明，所制得的磁铁矿 NPs 的物相不受使用各种碱的影响，但其结晶尺寸受到了影响。结果发现，二元碱的结晶尺寸最小，单碱基的结晶尺寸一般，而弱碱基的结晶尺寸最大。紫外-可见吸收光谱研究表明，随着纳米粒子尺寸的减小，吸收率和能隙也随之增大。制备的磁铁矿 NPs 被用来制造聚合物基纳米复合材料，用作低能量 X 射线的防护罩，而且重量轻。利用 XRD、原子力显微镜（AFM）和傅立叶变换红外光谱对这些样品进行了鉴定。晶体尺寸比磁铁矿 NPs 稍大。这与原子力显微镜的结果一致。在傅立叶变换红外光谱的结果中观察到了两相之间的干扰。研究了磁铁矿 NPs 的大小对衰减测试、线性衰减系数、质量衰减系数、半值层和平均自由路径的影响。结果表明，在一定范围的低工作电压下，随着用作增强相的磁铁矿 NPs 粒径的减小，使用人造屏蔽的效率会提高。
{"title":"Nanocomposite-Supported Polymeric Composites Prepared with Different Deposition Bases: Characterization and Application in X-ray Shielding","authors":"Shaymaa Mohammed Fayyadh, A. Ben Ahmed","doi":"10.3390/physics6010022","DOIUrl":"https://doi.org/10.3390/physics6010022","url":null,"abstract":"This study deals with the preparation of magnetite nanoparticles (NPs) via a coprecipitation method using several precipitation bases: binary precipitator (NH4OH), mono precipitator (NaOH), and weak precipitator (Ca(OH)2). The prepared magnetite NPs were identified using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis, surface area analysis, magnetic properties, Fourier-transformed infrared spectra (FT-IR), and ultra-violet UV–visible spectra. As a result, the phases of the produced magnetite NPs were unaffected by the use of various bases, but their crystallite sizes were affected. It was found that the binary base provided the smallest crystallite size, the mono base provided an average size, and the weak base provided the largest crystallite size. The UV–visible absorption spectroscopy investigation revealed that the absorption and the energy gap rose with a reduction in nanoparticle size. The prepared magnetite NPs were used to manufacture polymeric-based nanocomposites employed as protective shields from low-energy X-rays that are light in weight. These samples were identified using XRD, atomic force microscopy (AFM), and FT-IR spectroscopy. The crystallite size was slightly larger than it was in the case of magnetite NPs. This is consistent with the results of AFM. The interference between the two phases was observed in the results of the FT-IR spectra. The effects of the size of the magnetite NPs on the attenuation tests, linear attenuation coefficient, mass attenuation coefficient, half-value layer, and mean free path were investigated. The results showed that the efficiency of using manufactured shields increases with the decrease in the NPs size of the magnetite used as a reinforcement phase for a range of low operating voltages.","PeriodicalId":20136,"journal":{"name":"Physics","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2024-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140266834","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
At energy lower than 2 eV, the dispersion law of the electrons in a graphene sheet presents a linear dependence of the energy on the kinetic momentum, which is typical of photons and permits the description of the electrons as massless particles by means of the Dirac equation and the study of massless particles acted upon by forces. We analytically solve the Dirac equation of an electron in a graphene disk with radius of 10,000 atomic units pierced by a magnetic field and find the eigenenergies and eigenstates of the particles for spin up and down. The magnetic field ranges within three orders of magnitude and is found to confine the electron in the disk. States with a relatively large total angular momentum exist and can be considered in a vorticose condition; these states are seen to peak at different distances from the disk centre and can be used to store few bit of information.
在能量低于 2 eV 时，石墨烯薄片中电子的色散定律呈现出能量与动量的线性关系，这是光子的典型特征，因此可以通过狄拉克方程将电子描述为无质量粒子，并对受力作用的无质量粒子进行研究。我们分析求解了电子在磁场穿透的半径为 10,000 原子单位的石墨烯圆盘中的狄拉克方程，并找到了粒子自旋向上和向下的特征能和特征态。磁场的范围在三个数量级之内，并发现磁场将电子限制在圆盘中。具有相对较大总角动量的状态是存在的，可以在涡旋条件下考虑；这些状态在距离磁盘中心不同的距离处达到峰值，可以用来存储少量信息。
{"title":"Large Angular Momentum States in a Graphene Film","authors":"P. P. Corso, D. Cricchio, E. Fiordilino","doi":"10.3390/physics6010021","DOIUrl":"https://doi.org/10.3390/physics6010021","url":null,"abstract":"At energy lower than 2 eV, the dispersion law of the electrons in a graphene sheet presents a linear dependence of the energy on the kinetic momentum, which is typical of photons and permits the description of the electrons as massless particles by means of the Dirac equation and the study of massless particles acted upon by forces. We analytically solve the Dirac equation of an electron in a graphene disk with radius of 10,000 atomic units pierced by a magnetic field and find the eigenenergies and eigenstates of the particles for spin up and down. The magnetic field ranges within three orders of magnitude and is found to confine the electron in the disk. States with a relatively large total angular momentum exist and can be considered in a vorticose condition; these states are seen to peak at different distances from the disk centre and can be used to store few bit of information.","PeriodicalId":20136,"journal":{"name":"Physics","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140087103","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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