物理最新文献

{"title":"Analytical and numerical investigations of optimal control techniques for managing Ebola virus disease","authors":"W. Ahmad,&nbsp;H. Ullah,&nbsp;M. Rafiq,&nbsp;A. I. K. Butt,&nbsp;N. Ahmad","doi":"10.1140/epjp/s13360-025-06251-x","DOIUrl":"10.1140/epjp/s13360-025-06251-x","url":null,"abstract":"<div><p>Ebola virus disease, often referred to as Ebola hemorrhagic fever, is one of the deadliest viral infections, posing a severe global health threat. It typically originates from human contact with domestic or wild animals and spreads through direct and indirect human contact, making containment highly challenging. Managing and controlling the spread of Ebola disease remains a significant challenge in epidemic response efforts. This study introduces a novel compartmental model to examine Ebola disease transmission dynamics and the effectiveness of control strategies. We conduct a mathematical analysis to ensure the model’s well-posedness and explore its stability properties. The theoretical results are verified using three numerical methods: the Euler’s method, the fourth-order Runge–Kutta method, and the non-standard-finite-difference method. Furthermore, the impact of time-invariant vaccination and quarantine rates on the epidemic is analyzed using the non-standard-finite-difference approach. A sensitivity analysis is conducted on the model to identify the most influential parameters affecting disease transmission. Additionally, we formulate an optimal control problem to identify effective, time-dependent strategies for Ebola vaccination and quarantine measures. As a novel contribution, our findings emphasize the potential of these control strategies in reducing both infection rates and associated costs, with a particular focus on the most reliable non-standard finite difference scheme. The application of forward and backward-in-time non-standard finite difference method ensures numerical stability and preserves essential biological properties. Numerical simulations demonstrate that a combination of effective vaccination and quarantine measures, and public awareness can accelerate the control of Ebola virus disease. Overall, this study provides a comprehensive approach to modeling, analyzing, and controlling Ebola virus disease by integrating advanced mathematical techniques with practical disease management strategies.</p></div>","PeriodicalId":792,"journal":{"name":"The European Physical Journal Plus","volume":"140 4","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143861395","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Compact star modeling in f(T) gravity with gravitational decoupling","authors":"U. A. Khokhar,&nbsp;Z. Yousaf","doi":"10.1140/epjp/s13360-025-06245-9","DOIUrl":"10.1140/epjp/s13360-025-06245-9","url":null,"abstract":"<div><p>This work examines how complexity affects time-independent, spherical symmetric celestial systems using a radial metric distortion approach (commonly referred to be minimal geometric deformation) in <i>f</i>(<i>T</i>) theory, where <i>T</i> is torsion scalar. We illustrate that the complexity factor, a scalar function derived by dividing the Riemann tensor perpendicularly, has a supplementary feature. The entire complexity of an entity with two associated fluid distributions is just a combination of the complexities associated with each fluid. This work uses the radial metric distortion method to create astrophysically feasible models of anisotropic matter, based on the Tolman and Buchdahl models. The two frameworks generate qualitatively equivalent features for every non-null value of the decoupling constant <span>((0le beta &lt;1))</span>, while the magnitudes may differ significantly. Remarkably, both models maintain their anisotropic characteristics even after approaching the zero-complexity condition <span>((beta =1))</span>. In conclusion, we investigate the possible accuracy of these new solution categories in representing actual compact structures by delving into their physical ramifications.</p></div>","PeriodicalId":792,"journal":{"name":"The European Physical Journal Plus","volume":"140 4","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143856633","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Artificial intelligent focusing of a microbeam system based on reinforcement learning","authors":"Yanlin Li,&nbsp;Hongjin Mou,&nbsp;Wei Zhang,&nbsp;Jinlong Guo,&nbsp;Shi An,&nbsp;Guanghua Du,&nbsp;Xiaojun Liu","doi":"10.1140/epjp/s13360-025-06221-3","DOIUrl":"10.1140/epjp/s13360-025-06221-3","url":null,"abstract":"<div><p>Ion microbeam facility is a highly effective tool for precise sample irradiation, ion beam micro-modification, ion beam analysis, and other applications at micron and nanometer scale. However, achieving high-resolution beam spots requires meticulous adjustment of the microslit setting, beam transport and magnetic focusing field, which is even time-consuming for well-trained technicians. Nowadays, most of the beamline instruments and power supplies support remote control and automatic adjustment, which promotes the application of artificial intelligence to microbeam formation. In this work, we simulated the 50 MeV proton microbeam system with Oxford triplet lens configuration using a homemade ion optics package, which can generate data about any number of ions passing through quadrupole magnets. Then, an agent interacted with the system and generated large amounts of data. The data was used to train a deep Q-Network (DQN) model. Ultimately, we used the model to accomplish the intelligent focusing function on the simulated microbeam system. Comparative results show that the error between our model and the classic method is less than 0.3%.</p></div>","PeriodicalId":792,"journal":{"name":"The European Physical Journal Plus","volume":"140 4","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143861099","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The effect of higher dimensions on the collapse of self-gravitating fluids","authors":"Robert S. Bogadi,&nbsp;Andronikos Paliathanasis,&nbsp;Megandhren Govender","doi":"10.1140/epjc/s10052-025-14188-9","DOIUrl":"10.1140/epjc/s10052-025-14188-9","url":null,"abstract":"<div><p>We apply general relativity in higher dimensions to the collapse of an unstable massive body. A general solution is obtained for the heat flux boundary condition in n-dimensions. The temporal function obtained is then used to complete the description of an unstable neutron star which collapses from an initial static configuration. A Finch–Skea ansatz together with a linear equation of state was used to obtain the static configuration which is a solution of the static field equations. It is found that the collapse time is reduced in higher dimensions. The energy densities generally increase with dimension, although they tend to coalesce at horizon formation. The surface heat flux also coalesces near horizon formation with extra dimensions reducing the heat flux.\u0000</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"85 4","pages":""},"PeriodicalIF":4.2,"publicationDate":"2025-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-025-14188-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143861138","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Non-radial oscillations of hadronic neutron stars, quark stars, and hybrid stars: calculation of f, p, and g mode frequencies","authors":"Atanu Guha,&nbsp;Debashree Sen,&nbsp;Chang Ho Hyun","doi":"10.1140/epjc/s10052-025-14183-0","DOIUrl":"10.1140/epjc/s10052-025-14183-0","url":null,"abstract":"<div><p>The composition and equation of state (EoS) of dense matter relevant to compact stars are quite inconclusive. However, certain observational constraints on the structural properties of compact stars help us constrain the EoS to a fair extent. Moreover, gravitational asteroseismology gives a notion of the composition and EoS of compact stars. The next generation gravitational wave (GW) detectors are likely to detect several oscillation mode frequencies of the GWs. In this work we compute the fundamental (<i>f</i>) and the first pressure (<span>(p_1)</span>) mode frequencies (<span>(f_f)</span> and <span>(f_{p1})</span>, respectively) with different compositions viz., hadronic, quark, and hybrid star (HS) matter. For HSs, we also study the gravity (<i>g</i>) mode frequency (<span>(f_g)</span>). For each phase we also study the correlation between the oscillation frequencies of 1.4 <span>(M_{odot })</span> and 2.01 <span>(M_{odot })</span> compact stars with other different properties. We find that various possible composition of compact stars substantially affects the oscillation frequencies. However, the mass-scaled angular <i>f</i> mode frequency (<span>(omega _f M)</span>) varies universally with compactness (<i>C</i>) for all hadronic, quark and hybrid stars. The <i>f</i> mode frequency (<span>(f_{f_{1.4}})</span>) of the canonical 1.4 <span>(M_{odot })</span> compact star, obtained with different composition, is quite correlated with the canonical radius (<span>(R_{1.4})</span>) and tidal deformability (<span>(varLambda _{1.4})</span>) while <span>(f_{p_{1.4}})</span> is well correlated with slope parameter of the symmetry energy. We also show that <span>(f_{g_{1.4}})</span> of the HSs varies almost linearly with <span>(varLambda _{1.4})</span>. Should <i>g</i> modes be detected, they could not only support the existence of HSs, but <span>(f_g)</span> could be useful to understand the strength of quark repulsion in HSs.\u0000</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"85 4","pages":""},"PeriodicalIF":4.2,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-025-14183-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143856679","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Difference frequency generation in CdSe quantum dots","authors":"Komal Jain,&nbsp;Deepti Maikhuri,&nbsp;Anshuman Sahai","doi":"10.1007/s00340-025-08462-7","DOIUrl":"10.1007/s00340-025-08462-7","url":null,"abstract":"<div><p>We have investigated the second-order nonlinear susceptibility associated with difference frequency generation in singly electron charged CdSe/ZnS, CdSe/ZnSe, CdSe/MgS &amp; CdSe/MgSe quantum dots via intersublevel transitions in the conduction band. The confined energy levels in the dots are calculated in the effective-mass approximation by solving the three-dimensional Schrodinger equation. The second-order nonlinear susceptibility coefficients in the conduction band DFG processes are then determined using density matrix approach. As the dot radius increases, the DFG susceptibility spectrum shifts towards lower energy side. Also, we observe that, the peak height of the DFG spectrum increases slightly with increasing dot radius. For CdSe/ZnS, CdSe/ZnSe, CdSe/MgS quantum dots the second order nonlinear susceptibility associated with DFG is found to be one order higher (≈10⁻¹⁰ m/V) in contrast to that of the bulk CdSe (≈10⁻¹¹ m/V). We observed that second-order nonlinear difference frequency generation processes depend on the polarization state of incident photon beam, dot size and the surrounding matrix.</p></div>","PeriodicalId":474,"journal":{"name":"Applied Physics B","volume":"131 5","pages":""},"PeriodicalIF":2.0,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143856660","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Wormholes-like solutions in quantum cosmology with radiation, negative cosmological constant and Pöschl–Teller potential","authors":"G. A. Monerat,&nbsp;F. G. Alvarenga,&nbsp;G. Oliveira-Neto,&nbsp;E. V. Corrêa Silva,&nbsp;J. C. G. Tedesco,&nbsp;A. Monteiro,&nbsp;N. M. N. da Rocha","doi":"10.1140/epjp/s13360-025-06257-5","DOIUrl":"10.1140/epjp/s13360-025-06257-5","url":null,"abstract":"<div><p>In this work, we analyze a quantum cosmology model with three components: radiation fluid; negative cosmological constant term; and a Bose–Einstein condensate described by the Pöschl–Teller potential. At the classical level, all cosmological solutions of the model exhibit big bang-type singularities. Through quantization in minisuperspace, the singularities are removed by wavefunction solutions of the Universe in the form of wormholes from the Wheeler–DeWitt equation. These solutions and the corresponding energy spectrum are obtained using the Galerkin method. We also construct normalized wave packets and verify, within the many-worlds interpretation of quantum mechanics, that the expected value of the Universe’s scale factor never vanishes.</p></div>","PeriodicalId":792,"journal":{"name":"The European Physical Journal Plus","volume":"140 4","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143852533","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bohr Hamiltonian with energy-dependent (ED) inverse square potential for (gamma )-unstable nuclei","authors":"K. R. Ajulo,&nbsp;K. J. Oyewumi,&nbsp;A. Lahbas,&nbsp;M. M. Orosun,&nbsp;T. V. Targema,&nbsp;G. W. Joseph,&nbsp;B. Sebo,&nbsp;W. Sali,&nbsp;S. I. Akinsola,&nbsp;S. O. Ajibade","doi":"10.1140/epjp/s13360-025-06278-0","DOIUrl":"10.1140/epjp/s13360-025-06278-0","url":null,"abstract":"<div><p>In this paper, analytical solutions of Bohr Hamiltonian for <span>(gamma )</span>-unstable nuclei via energy-dependent (ED) inverse square potential are obtained. A linear ED potential is employed to minimize the <span>(beta )</span>-fluctuation which occurs during the <span>(beta )</span> collective excitation motion of the nuclei. The ED inverse square potential is shown to override the general problem associated with ED and also with the standard version of Bohr Hamiltonian without ED. The present model is well represented by <span>(^{118-134})</span>Xe isotope chain. For <span>(^{132})</span>Xe and <span>(^{134})</span>Xe spectra fits, standard errors of <span>(sigma =0.32)</span> and <span>(sigma =0.13)</span> are recorded, respectively, compared to <span>(sigma =0.42)</span> and <span>(sigma =0.19)</span> from previous studies using inverse square potential without ED. Within the framework of Bohr Hamiltonian for <span>(gamma )</span>-unstable nuclei, these results indicate that the present ED model can serve as a corrective approach to previous work using inverse square potential without energy dependence.</p></div>","PeriodicalId":792,"journal":{"name":"The European Physical Journal Plus","volume":"140 4","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143852556","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impact of diameter-to-length ratio on mechanical fatigue and cyclic behavior of gold nanowires: a molecular dynamics study","authors":"Muhammad Salsabil Nur Gunawan,&nbsp;Adam Fajri Asyidik,&nbsp;Tabina Putri Pintoro,&nbsp;Iwan Halim Sahputra","doi":"10.1140/epjb/s10051-025-00924-3","DOIUrl":"10.1140/epjb/s10051-025-00924-3","url":null,"abstract":"<div><p>Gold nanowires (AuNWs) exhibit exceptional mechanical properties, making them promising for nanoscale electronics. However, their mechanical reliability under cyclic loading, particularly the effects of diameter-to-length ratio and pulling rate, remains insufficiently understood. This study addresses this knowledge gap by investigating the impact of these factors on the mechanical fatigue behavior of AuNWs using molecular dynamics simulations. Stress–strain analyses and common neighbor analysis (CNA) were employed to assess mechanical responses and structural evolution during cyclic deformation. The findings reveal that smaller AuNWs (e.g., 1 nm diameter) undergo rapid strain hardening due to limited dislocation nucleation, resulting in high stress capacity but brittle failure. In contrast, larger AuNWs (3–9 nm diameters) exhibit greater plastic accommodation and localized deformation, delaying failure and enhancing mechanical stability. The pulling rate further modulates these behaviors, with higher rates increasing peak stresses and lower rates promoting plastic relaxation. By elucidating the interplay between diameter, loading conditions, and fatigue behavior, this study provides novel insights into the structural reliability of AuNWs, offering a foundation for their optimized design in advanced nanoscale applications.</p><h3>Graphical abstract</h3><div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":787,"journal":{"name":"The European Physical Journal B","volume":"98 4","pages":""},"PeriodicalIF":1.6,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143856620","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Similar transitions and extreme events in non-identical neuron models","authors":"S Dinesh Vijay,&nbsp;K Thamilmaran,&nbsp;A Ishaq Ahamed","doi":"10.1007/s12043-025-02909-4","DOIUrl":"10.1007/s12043-025-02909-4","url":null,"abstract":"<div><p>This study investigates the phenomenon of abnormally large amplitude intermittent spikes in a memristive Hindmarsh–Rose (MHR) neuron model. The analysis focusses on the effects of coupling strength variations between mutually coupled FitzHugh–Nagumo (FHN) and MHR neuron models. Both neuron models exhibit similar transitions at a critical coupling strength, the FHN neuron displays intermittent oscillations, whereas the MHR neuron occasionally generates intermittent spikes of significantly larger amplitude. The occurrence of extreme events within these spikes was validated using the probability distribution function (PDF). Furthermore, the two-parameter phase diagrams of the membrane input currents and coupling strength enabled the identification of extreme event (EE) and non-extreme event (NEE) regions in the MHR neuron model. The study also explores the underlying mechanisms responsible for the extreme amplitude of spikes observed in the MHR neuron.</p></div>","PeriodicalId":743,"journal":{"name":"Pramana","volume":"99 2","pages":""},"PeriodicalIF":1.9,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143852509","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}