物理最新文献

{"title":"Viscosity dissipation and Brinkman–Bénard convection with thermal anisotropy: stability studies in both linear and nonlinear","authors":"Anil Kumar,&nbsp;D. Bhargavi,&nbsp;P. K. Mourya,&nbsp;P. G. Siddheshwar","doi":"10.1140/epjp/s13360-025-06788-x","DOIUrl":"10.1140/epjp/s13360-025-06788-x","url":null,"abstract":"<div><p>This study presents both linear and nonlinear stability analyses of Brinkman–Bénard convection in a porous medium, considering the effects of thermal anisotropy. The flow occurs between two walls maintained at uniform but different temperatures. The critical Rayleigh number is examined, including variations in the Darcy number, porosity, Prandtl number, and anisotropic thermal conductivity, with both linear and nonlinear stability regimes analyzed. Contour plots of streamlines and isotherms are provided to visualize fluid and heat flow directions. The results demonstrate that the presence of the porous medium inhibits convection and reduces the cell size at the onset of instability. Additionally, thermal anisotropy stabilizes the system, with the region of subcritical instability shrinking as the anisotropy parameter increases. While the linear stability analysis does not reveal any significant impact of viscous dissipation, the nonlinear stability analysis shows that viscous dissipation destabilizes the system. These findings contribute to a deeper understanding of the interplay between thermal anisotropy, porosity, and convection behavior in porous media, with implications for various engineering and geophysical applications.</p></div>","PeriodicalId":792,"journal":{"name":"The European Physical Journal Plus","volume":"140 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144990437","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":"Linearized renormalization","authors":"L. L. Salcedo","doi":"10.1140/epjc/s10052-025-14658-0","DOIUrl":"10.1140/epjc/s10052-025-14658-0","url":null,"abstract":"<div><p>Using an infinitesimal approach, this work addresses the renormalization problem to deal with the ultraviolet divergences arising in quantum field theory. Under the assumption that the action has already been renormalized to yield an ultraviolet-finite effective action that satisfies a certain set of renormalization conditions, we analyze how the action must be adjusted to reproduce a first-order change in these renormalization conditions. The analysis then provides the change that is induced on the correlation functions of the theory. This program is successfully carried out in the case of super-renormalizable theories, namely, a scalar field with cubic interaction in four space-time dimensions and with quartic interaction in three space-time dimensions. Relying on existing results in the theory of perturbative renormalization, we derive explicit renormalized expressions for these theories, each of which involves only a finite number of graphs constructed with full propagators and full <i>n</i>-point vertices. The renormalizable case is analyzed as well; the derived expressions are ultraviolet finite as the regulator is removed but cannot be written without a regulator. In this sense, the renormalization is not fully explicit in the renormalizable case. Nevertheless, a perturbative solution of the equations starting from the free theory provides the renormalized Feynman graphs, similar to the BPHZ program. For compatibility with the preservation of the renormalization conditions, a projective renormalization scheme, as opposed to a minimal one, is also introduced. The ideas developed are extended to the study of the renormalization of composite operators and the Schwinger–Dyson equations.\u0000</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"85 9","pages":""},"PeriodicalIF":4.8,"publicationDate":"2025-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-025-14658-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144990463","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":"Greybody factor for massive scalar field in charged black hole","authors":"Ratchaphat Nakarachinda,&nbsp;Suppawit Polkong,&nbsp;Pitayuth Wongjun","doi":"10.1140/epjp/s13360-025-06756-5","DOIUrl":"10.1140/epjp/s13360-025-06756-5","url":null,"abstract":"<div><p>The greybody factor of a massive scalar field in the Reissner–Nordström black hole is investigated using the Wentzel–Kramers–Brillouin (WKB) approximation and rigorous bound methods. We found that the transmission probability and behavior of the potential are directly related in such a way that the higher the potential, the lower the greybody factor. Both methods achieve a similar conclusion, which states that the greybody factor and the mass of the scalar field have an inverse relationship. This can be interpreted in a similar way in quantum mechanics, namely the scalar field with the higher mass will encounter a stronger interaction from the potential and then it is more difficult to penetrate through the potential barrier. The rigorous bound has the advantage of not only being possible to calculate analytically, but also being applicable to a wider range of parameter values compared to the standard WKB approximation.</p></div>","PeriodicalId":792,"journal":{"name":"The European Physical Journal Plus","volume":"140 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144998398","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":"Bilinear neural network solutions for nonlinear waves in the Sawada–Kotera model studied in heat transfer","authors":"Syed Kamran Naqvi,&nbsp;Ibtisam Aldawish,&nbsp;Syed T. R. Rizvi,&nbsp;Aly R. Seadawy","doi":"10.1140/epjp/s13360-025-06781-4","DOIUrl":"10.1140/epjp/s13360-025-06781-4","url":null,"abstract":"<div><p>In this study, the bilinear neural network method (BNNM) is employed to obtain exact analytical solutions of the (2 + 1)-dimensional bidirectional Sawada–Kotera (bSK) equation. BSK describes the evolution and interaction of nonlinear wave structures propagating simultaneously in opposite spatial directions within a multidimensional medium. BNNM approach begins with the generalized Hirota bilinear method to transform the equation into bilinear form, after which the BNNM-integrating classical bilinear theory with neural network (NN) architectures is applied to derive closed-form solutions. In this framework, the trial functions are modeled through layered NNs, where activation functions and weight matrices determine the solution structures; the “3-2-1” and “3-3-1” architectures are used to generate diverse waveforms, including lump solutions, lump-kink interactions, rogue waves, breather–lump solitons, and periodic waves. The results are visualized through contour plots, and 3D surface graphs to capture the waves geometrical and dynamical attributes. This work is significant as it demonstrates that BNNM not only recovers known wave patterns but also generates new classes of test functions, offering a flexible and computationally efficient framework for exploring multidimensional nonlinear wave phenomena. The method has broad applicability in nonlinear optics, plasma physics, fluid dynamics, geophysical flows, and acoustics, where understanding the formation, interaction, and stability of localized and periodic structures is of practical importance.</p></div>","PeriodicalId":792,"journal":{"name":"The European Physical Journal Plus","volume":"140 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144990431","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":"Nitrogen ion irradiation of carbon thin films using a dense plasma focus: enhanced doping and structural modifications","authors":"H. P. Wante,&nbsp;S. L. Yap,&nbsp;K. Y. Tsung,&nbsp;H. Y. Tan,&nbsp;L. K. Lim,&nbsp;S. C. Ezike,&nbsp;Siaw Foon Lee","doi":"10.1140/epjp/s13360-025-06761-8","DOIUrl":"10.1140/epjp/s13360-025-06761-8","url":null,"abstract":"<div><p>Activated carbons (ACs) are widely used in supercapacitors and batteries due to their high surface area, well-developed porosity, cost-effectiveness, and scalability, making them ideal for commercial energy storage applications. In this study, carbon derived from coconut shells was processed into a thin film on a nickel substrate, synthesized via doctor blade deposition, and subjected to nitrogen ion beam irradiation (6, 12, and 24 shots) using a 3.0 kJ dense plasma focus (PF) device, operated at 2.54 kJ to produce carbon nitride. The PF device generated a high-energy ion beam (~ 72.40 keV) at 1.5 mbar within nanoseconds, with a flux of 7.2 × 10²⁷ ions m⁻² s⁻¹ and a fluence of 6.4 × 10¹⁹ ions m⁻². The Lee model code estimated a nitrogen ion beam energy of 71.0 keV, closely matching the measured 72.40 keV, confirming the model’s reliability. EDX analysis revealed significant spectral changes, with nitrogen doping reaching 7.93% after 24 shots. The optimum doping content per shot is highest at lower shot counts, reaching 1.18% per shot for the 6-shot sample, and gradually decreasing with additional shots. FTIR confirmed nitrogen-related functional groups (C≡N, S − C≡N, and N = C = S), indicating successful incorporation of nitrogen. FESEM showed pores, bulges, blunt edges, and adatoms after nitrogen ion irradiation, indicating morphological changes. XRD of the 24-shot sample revealed new peaks at 52° and 76°, corresponding to the (004) and (110) planes, associated with nitrogen incorporation and surface modification. The crystallite size increased from 6.27 nm to 11.16 nm after 24 shots of nitrogen ion irradiation, indicating enhanced crystallinity. An interlayer spacing of 0.340 nm (3.40 Å), approaching the graphitic value of 3.35 Å, was observed after 24 shots, indicating the onset of graphitization. These findings confirm effective nitrogen doping and significant structural modifications.</p></div>","PeriodicalId":792,"journal":{"name":"The European Physical Journal Plus","volume":"140 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjp/s13360-025-06761-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144998397","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Influence of spin-orbit coupling mode of vector vortex beam on the electromagnetically induced transparency and absorption in rubidium vapor","authors":"Samim Akhtar,&nbsp;Rakiba Rahaman,&nbsp;Md Jalaluddin,&nbsp;Jayanta K. Saha,&nbsp;Md. Mabud Hossain","doi":"10.1140/epjp/s13360-025-06763-6","DOIUrl":"10.1140/epjp/s13360-025-06763-6","url":null,"abstract":"<div><p>In this article, we experimentally study the influence of the vector vortex beam (VVB)-assisted spin-orbit coupling (SOC) mode on the electromagnetically induced transparency (EIT) and absorption (EIA) spectra in multi-level <span>(Lambda )</span>- and V-type schemes formed by <span>(^{85})</span>Rb-D<span>(_{2})</span> hyperfine transitions. We have observed that the coherent signals (EIT and EIA) formed in the Doppler-broadened non-vortex probe absorption profile are significantly modulated by the orbital angular momentum (OAM) of the pump VVB. Furthermore, it is shown that the resolution of these coherent signals can be maximized by adjusting the ratio of the pump-probe fields strength for each OAM number. It is also found that each OAM corresponds to a unique pump-probe strength ratio at which the EIT and EIA signals attain their maximum amplitude. The experimental results regarding the substantial modulation of the atomic coherent signals with the variation of OAM indicate that the subluminal (slow light) and superluminal (fast light) propagation of the non-vortex probe beam inside an atomic medium can efficiently be controlled by the SOC mode of the pump VVB.</p><h3>Graphical abstract</h3><div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":792,"journal":{"name":"The European Physical Journal Plus","volume":"140 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144990435","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":"Nanostructure science and vortex physics of YBa2Cu3O7 for practical high-performance coated conductor","authors":"Tomoya Horide,&nbsp;Yutaka Yoshida","doi":"10.1140/epjb/s10051-025-01025-x","DOIUrl":"10.1140/epjb/s10051-025-01025-x","url":null,"abstract":"<div><p>YBa₂Cu₃O₇ coated conductors are under active development for high-field magnet, nuclear magnetic resonance, and fusion energy applications. Extensive research efforts have focused on enhancing the performance of these conductors. Among these, significant attention has been given to vortex physics, nanoscale science, and process optimization. Grain boundaries, which act as weak link, degrade the critical current density. To mitigate this, YBa₂Cu₃O₇ films are deposited on textured metal substrates with highly oriented buffer layers. To further enhance the critical current density, nanoscale pinning centers are incorporated via self-organization during film growth. The critical current density is governed by multiscale factors involving the nanorod structure at atomic, nanoscale, and micrometer levels. Nanorod morphology and density are controlled, and additional types of pinning centers are introduced to prepare hybrid pinning centers. These nanorods alter the chemical bonding and electronic structure of YBa₂Cu₃O₇ at their interfaces. The influence of nanocomposite formation on the superconducting transition temperature is discussed based on oxygen vacancies formation induced by tensile strain. Atomic scale nature of nanostructure and macroscopic homogeneity of properties related to the process variation should be investigated to advance the coated conductor technology. The integration of advanced characterization techniques, computational simulations, and artificial intelligence technology is effective in achieving a deeper understanding and more precise control of the underlying vortex pinning and the macroscopic phenomena caused by process variation.</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 9","pages":""},"PeriodicalIF":1.7,"publicationDate":"2025-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144998577","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":"Epidemic models with controlling actions: a Gibbs free energy approach","authors":"A. A. Nogueira,&nbsp;A. S. S. Santos,&nbsp;G. B. de Gracia","doi":"10.1140/epjp/s13360-025-06789-w","DOIUrl":"10.1140/epjp/s13360-025-06789-w","url":null,"abstract":"<div><p>As is well known, our understanding of epidemic dynamics relies heavily on compartmental mathematical models, such as the SIR and SEIR frameworks, which categorize individuals according to their disease status. A central concept emerging from these models is the <i>reproductive number</i> (the average number of individuals that a single infected person transmits the disease to during their infectious period). In this work, we explore the relationship between the reproductive number and the Gibbs free energy, drawing an analogy between epidemic spread and spontaneous or catalyzed chemical reactions, as both processes are governed by analogous mathematical structures. Building on this connection, we examine the relation <span>(Delta G = -E ln (R_t))</span>, which links the effective reproductive number <span>(R_t)</span> to the Gibbs free energy change <span>(Delta G)</span>. This formulation suggests a novel investigative approach: interpreting epidemic progression as a form of phase transition in the thermodynamic sense, thereby opening new perspectives for understanding critical transitions in infectious disease dynamics.</p></div>","PeriodicalId":792,"journal":{"name":"The European Physical Journal Plus","volume":"140 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjp/s13360-025-06789-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144990433","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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-Fraunhofer current driven phase dynamics and voltage characteristics in Josephson junction ladder","authors":"Rahul Kumar Saha,&nbsp;Ajay Kumar Ghosh","doi":"10.1140/epjp/s13360-025-06797-w","DOIUrl":"10.1140/epjp/s13360-025-06797-w","url":null,"abstract":"<div><p>Numerically, the variation of voltage drop (<i>V</i>) and phase fluctuations <span>(Delta theta)</span> in a Josephson junction ladder (JJL) has been studied as a result of an external modulated currents <i>I</i>(<i>i</i>, <i>t</i>) using random field XY model (RFXY). A disordered random magnetic field is introduced in a <i>JJL</i>. Asymmetry in the non-Fraunhofer current–voltage curve is obtained for different sizes of system and fields. Phase fluctuation, <span>(Delta theta)</span>, increases with the increase of amplitude of external current, <span>(I_{0})</span>. Increasing the pinning strength, <i>W</i>, a saturation in <i>V</i> is possible for several constant <span>(I_{0})</span>.\u0000</p></div>","PeriodicalId":792,"journal":{"name":"The European Physical Journal Plus","volume":"140 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144998395","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":"A new generative framework for fast parametric modeling of (X-) and (gamma -)ray energy spectra using VAE","authors":"I. Meleshenkovskii,&nbsp;T. Sendra,&nbsp;E. Mauerhofer,&nbsp;V. Vigneron","doi":"10.1140/epjp/s13360-025-06679-1","DOIUrl":"10.1140/epjp/s13360-025-06679-1","url":null,"abstract":"<div><p>This paper proposes a variational autoencoder-based technique for the fast modeling of various <span>(X-)</span> or <span>(gamma -)</span>ray spectra, including the parametrization of the physical measurement conditions, and introduces the SpectroGAN simulation tool. The generated spectra reproduce the training data with high precision. Still, they may vary according to the parameters of interest, such as detector energy resolution, efficiency, attenuation, activity, enrichment, or isotopic composition. Our results demonstrate that machine learning-based spectra simulations have several potential advantages over Monte Carlo-based simulation methods. First, they are much faster and more efficient to calculate. Second, they can provide accurate spectra even if the expected conditions are not included in the training dataset. The data-based model can learn complex relationships between the detector characteristics, measurement configuration, and the spectrometric features examined (such as signature peaks of elements). Finally, they can generate large amounts of synthetic data for training other machine learning models, such as those used in data analysis or pattern recognition. Overall, the data-based spectrometry can be generalized to various other applied radiation measurement tasks, including passive and active non-destructive measurement techniques featuring prompt and delayed neutrons and or gamma-rays detection, PGNAA and PGAINS applications, offering new opportunities for measurement system configuration optimization, as well as detector design. Official implementation is available at https://github.com/Tarysa/fast-parametric-modeling-of-X-and-ray-energy-spectra-using-VAE.</p></div>","PeriodicalId":792,"journal":{"name":"The European Physical Journal Plus","volume":"140 9","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjp/s13360-025-06679-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144998396","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}