物理最新文献

{"title":"Some simple theories of gravity with propagating nonmetricity","authors":"Yusuke Mikura,&nbsp;Roberto Percacci","doi":"10.1140/epjc/s10052-025-14036-w","DOIUrl":"10.1140/epjc/s10052-025-14036-w","url":null,"abstract":"<div><p>We investigate symmetric metric-affine theories of gravity with a Lagrangian containing all operators of dimension up to four that are relevant to free propagation in flat space. Complementing recent work in the antisymmetric case, we derive the conditions for the existence of a single massive particle with good properties, in addition to the graviton.\u0000</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"85 4","pages":""},"PeriodicalIF":4.2,"publicationDate":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-025-14036-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143761721","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":"Controlled co-precipitation synthesis of Gd and Mn doped zinc tungstate: insights into structural, optical, magnetic behavior, and dielectric properties","authors":"Sadegh Azadmehr,&nbsp;Sanaz Alamdari,&nbsp;Majid Jafar Tafreshi,&nbsp;Zaighum Tanveer,&nbsp;Omid Mirzaee,&nbsp;Aliasghar Najafzadehkhoee,&nbsp;Jose J. Velázquez","doi":"10.1007/s00339-025-08399-w","DOIUrl":"10.1007/s00339-025-08399-w","url":null,"abstract":"<div><p>Gadolinium and manganese-doped zinc tungstate (ZnWO₄: Gd &amp; ZnWO₄: Mn (1 at%)) nanocrystals were successfully prepared using a simple co-precipitation method. The structural, morphological, and chemical properties of the materials were thoroughly investigated using X-ray diffraction (XRD), scanning/transmission electron microscopy (SEM/TEM), and energy dispersive X-ray (EDX) analysis. The crystallite sizes of the Gd-doped and Mn-doped samples were 46 nm and 59 nm, respectively. XRD analysis confirmed that both samples exhibited a single monoclinic phase crystal structure. The Gd-doping resulted in a more uniform particle size distribution and smoother surface morphology, which could enhance the optical and magnetic properties of the material. In contrast, Mn-doping led to the formation of more agglomerated particles with a rougher texture, potentially affecting the specific surface area and its interaction with external fields. SEM/TEM images also revealed an increase in average particle size with the Mn dopant. Optical properties, as measured by diffuse reflectance spectroscopy (DRS), showed a band gap of 3.79 eV for ZnWO₄: Gd and 3.40 eV for ZnWO₄: Mn. Magnetic measurements indicated enhanced magnetic properties for ZnWO₄: Mn compared to both pure ZnWO₄ and ZnWO₄: Gd. The dielectric properties, including the dielectric constant (εr), dielectric loss (tan δ), and AC conductivity, were studied over a frequency range from 100 Hz to 3 MHz at room temperature. The reduced coercivity observed in the Mn-doped sample suggests improved performance for potential applications in transformers, windings, and magnetic storage devices, where reduced core loss and enhanced efficiency are key requirements.This study not only enhances the understanding of the influence of Gd and Mn doping on ZnWO₄ properties but also opens up new possibilities for the development of multifunctional materials for advanced technological applications.</p><h3>Graphical Abstract</h3><div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":473,"journal":{"name":"Applied Physics A","volume":"131 5","pages":""},"PeriodicalIF":2.5,"publicationDate":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143749175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Nonmetricity-based hybrid self-gravitating compact stars with embedded class-one symmetry","authors":"Naveed Iqbal,&nbsp;S. Khan,&nbsp;Mohammad Alshammari,&nbsp;Wael W. Mohammed,&nbsp;M. Ilyas","doi":"10.1140/epjc/s10052-025-14102-3","DOIUrl":"10.1140/epjc/s10052-025-14102-3","url":null,"abstract":"<div><p>This work aims to explore the novel characteristics of a static hybrid transitional star with a spherical distribution of relativistic matter under the embedded class one metric framework. This theoretical stellar model is derived using the nonmetricity-inspired <span>(f(mathbb {Q}))</span> gravity, featuring a core-crust structure: a strange matter core embedded in a normal matter crust. Our model incorporates pressure anisotropy as an intrinsic characteristic of highly compact strange stars, a feature expected to arise in the super-dense regime. The equation of state, in its basic form, using the MIT bag model is employed to represent correlation between pressure and density in quark matter inside the star’s core. The development of this model involves selecting the temporal gravitational potential based on the Tolman–Kuchowicz ansatz, while the radial gravitational potential is determined using the Class One embedding formalism. We employed both analytical and graphical methods to assess the robustness and equilibrium of the presented stellar solution. We provide an in-depth description of the astrophysical features of the model and show that they fulfill regularity requirements. A key finding of this investigation is the absence of a core singularity within the anisotropic stellar formation. The solution matches the properties of the observed self-gravitating pulsar objects: SAX J1804.4-3658 (SS1), EXO1745-248, 4U1820-30, 4U1608-52, PSR J0740+6620, PSR J0030+0451, Cen X-4, and SAX J1804.4-3658 (SS2). \u0000</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"85 4","pages":""},"PeriodicalIF":4.2,"publicationDate":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-025-14102-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143749130","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":"Reconciling fractional entropy and black hole entropy compositions","authors":"Manosh T. Manoharan,&nbsp;N. Shaji","doi":"10.1140/epjc/s10052-025-14107-y","DOIUrl":"10.1140/epjc/s10052-025-14107-y","url":null,"abstract":"<div><p>This study investigates the implications of adopting fractional entropy in the area law framework and demonstrates its natural alignment with an isothermal description of black hole composition. We discuss the Zeroth law compatibility of the fractional entropy and define an empirical temperature for the horizon. We highlight the distinction between the empirical and conventional Hawking temperatures associated with the black holes. Unlike the Hawking temperature, this empirical temperature appears universal, and its proximity to the Planck temperature suggests a possible quantum gravity origin. We also establish the connection between these temperatures. Furthermore, extending the conventional fractional parameter <i>q</i>, constrained between 0 and 1, we establish that any positive real number can bound <i>q</i> under the concavity condition, provided the log of micro-state dimensionality exceeds <span>(q-1)</span>. Specifically, for black holes, <span>(q = 2)</span>, necessitating micro-state dimensionality greater than <i>e</i>, thereby excluding the construction of black hole horizon states with two level bits or qubits. We also identify the connection between the validity of the second law and information fluctuation complexity. The second law requires that the variance of information content remain smaller than the area of the black hole horizon. This constraint naturally gives rise to a Boltzmann–Gibbs-like entropy for the black hole, which, in contrast to the canonical formulation, is associated with its mass rather than its area. Equilibrium distribution analysis uncovers multiple configurations, in which the one satisfying the prerequisites of probability distribution exhibits an exponent stretched form, revealing apparent deviation from the Boltzmann distribution.</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"85 4","pages":""},"PeriodicalIF":4.2,"publicationDate":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-025-14107-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143749132","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":"Information conservation in de Sitter tunneling","authors":"Baoyu Tan","doi":"10.1140/epjc/s10052-025-14101-4","DOIUrl":"10.1140/epjc/s10052-025-14101-4","url":null,"abstract":"<div><p>In this paper, we consider the three most general cases of progressive de Sitter spacetime. The charged and magnetic particles tunnel into the magnetically charged Reissner–Nordström de Sitter black hole (the most general case of a static black hole), the Kerr–Newman–Kasuya de Sitter black hole (the most general case of a rotating black hole), and Bardeen de Sitter black hole (black hole without singularities). We use Parikh–Wilczek method to calculate the radiation spectra of these black holes respectively, and find that they deviate from the pure thermal spectra, satisfying the unitary principle. Our results support the conservation of information and are generally true for all asymptotic de Sitter space-times.</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"85 4","pages":""},"PeriodicalIF":4.2,"publicationDate":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-025-14101-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143761723","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":"Bifurcation analysis and control of a modified continuum traffic flow model considering mixed motor vehicles and bicycles","authors":"WenHuan Ai,&nbsp;JianLi Fu,&nbsp;JingMing Zeng,&nbsp;DaWei Liu","doi":"10.1140/epjb/s10051-025-00898-2","DOIUrl":"10.1140/epjb/s10051-025-00898-2","url":null,"abstract":"<div><p>In urban studies, issues with traffic flow have always been a popular topic. We explore the propagation traits and evolution law of traffic flow, which can serve as a theoretical foundation for the planning and management of road traffic, starting with the theory of traffic flow bifurcation. We suggest a macroscopic traffic model that takes into account the frictional and obstructive disturbance based on the influence of traffic flow mixed motor vehicles and bicycles. The influence of vehicle speed, density, speed differential, and other parameters on the evolution law of macroscopic traffic flow is investigated by bifurcation analysis. From the viewpoint of the overall stability of the traffic system, the non-linear bifurcation theory is also employed to describe the non-linear traffic phenomena on the traffic flow of mixed motor vehicles and bicycles. The findings indicate that when a blocking disturbance is certain, the unstable region of the traffic flow gradually expands as non-motorized traffic flow increases, and when a frictional disturbance is certain, the unstable region of the traffic flow gradually expands as the blocking disturbance's duration gradually lengthens. It has been discovered that the nonlinear model can accurately capture the phenomenon of mixed motor vehicles and bicycles in the traffic flow through the analysis of the equilibrium point and local bifurcation. Finally, this paper suggests a non-linear feedback controller that delays or prevents the emergence of bifurcation points when added to the model. This controller serves as a theoretical foundation for future research on the impact of mixed motor vehicles and bicycles on the operational characteristics of traffic flow. Through simulation of density-time and phase plane diagrams, the model is confirmed to be able to describe the phenomena of traffic congestion and stopping in real traffic, providing a theoretical foundation for the mitigation of traffic congestion.</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":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143749235","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":"Energy conditions in (f(Q, L_m)) gravity","authors":"Y. Myrzakulov,&nbsp;O. Donmez,&nbsp;M. Koussour,&nbsp;S. Muminov,&nbsp;D. Ostemir,&nbsp;J. Rayimbaev","doi":"10.1140/epjc/s10052-025-14112-1","DOIUrl":"10.1140/epjc/s10052-025-14112-1","url":null,"abstract":"<div><p>We are experiencing a golden age of experimental cosmology, with exact and accurate observations being used to constrain various gravitational theories like never before. Alongside these advancements, energy conditions play a crucial theoretical role in evaluating and refining new proposals in gravitational physics. We investigate the energy conditions (WEC, NEC, DEC, and SEC) for two <span>(f(Q, L_m))</span> gravity models using the FLRW metric in a flat geometry. Model 1, <span>(f(Q, L_m) = -alpha Q + 2L_m + beta )</span>, features linear parameter dependence, satisfying most energy conditions while selectively violating the SEC to explain cosmic acceleration. The EoS parameter transitions between quintessence, a cosmological constant, and phantom energy, depending on <span>(alpha )</span> and <span>(beta )</span>. Model 2, <span>(f(Q, L_m) = -alpha Q + lambda (2L_m)^2 + beta )</span>, introduces nonlinearities, ensuring stronger SEC violations and capturing complex dynamics like dark energy transitions. While Model 1 excels in simplicity, Model 2’s robustness makes it ideal for accelerated expansion scenarios, highlighting the potential of <span>(f(Q, L_m))</span> gravity in explaining cosmic phenomena.\u0000</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"85 4","pages":""},"PeriodicalIF":4.2,"publicationDate":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-025-14112-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143761722","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":"High-energy proton beam generation via combined radiation pressure acceleration and laser wakefield acceleration in modulated plasma channels","authors":"Xin Chen,&nbsp;Lu Yang,&nbsp;Xiao-Nan Wang,&nbsp;Li Xiong,&nbsp;Peng-Fan Chen,&nbsp;Hai-Long Zhou,&nbsp;Xiao-Fei Lan,&nbsp;Yong-Sheng Huang,&nbsp;Yang-Fan He","doi":"10.1140/epjd/s10053-025-00977-0","DOIUrl":"10.1140/epjd/s10053-025-00977-0","url":null,"abstract":"<p>High-energy proton beams are essential for fundamental research and applied physics. The combined acceleration mechanism based on radiation pressure acceleration has made great progress in obtaining high-energy protons. However, Rayleigh–Taylor instability (RTI) is still a potential influencing factor that will limit the quality of high-energy proton beams. Different from the previous suppression and neglect of RTI, this paper introduces a parabolic density plasma channel to accelerate protons by virtue of the characteristics of RTI. Three-dimensional Particle-in-cell simulations reveal that this scheme achieves high-energy protons with cut-off energy of 39 <span>(textrm{GeV})</span>, total charge of 0.97 <span>(textrm{nC})</span>, and the emittance of 1.12 <span>(mathrm{{mm}};mathrm{{mrad}})</span> in both the <i>y</i> and <i>z</i> directions. There are locally distributed electrons in the parabolic density plasma channel, and the focusing field around them can effectively focus protons. Compared with the uniform density plasma channel, the parabolic density plasma channel can significantly improve the quality of the proton beam, which could offer significant guidance for the generation and application of high-energy proton beams.</p>","PeriodicalId":789,"journal":{"name":"The European Physical Journal D","volume":"79 4","pages":""},"PeriodicalIF":1.5,"publicationDate":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143749063","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":"The bosonic string spectrum and the explicit states up to level 10 from the lightcone and the chaotic behavior of certain string amplitudes","authors":"Igor Pesando","doi":"10.1140/epjc/s10052-025-13955-y","DOIUrl":"10.1140/epjc/s10052-025-13955-y","url":null,"abstract":"<div><p>We compute the irreps and their multiplicities of bosonic string spectrum up to level 10 and we give explicitly the on shell top level lightcone states which make the irreps. For the irreps up to three indexes and all the totally antisymmetric ones we give the general recipe and the full irreps. It turns out that lightcone is quite efficient in building these low indexes irreps once the top level states are known. For scalars and vectors we compute the multiplicity up to level 22 and 19 respectively. The first scalar at odd level appears at level 11. For the bosonic string in non critical dimensions we argue that at level <i>N</i> there are always states transforming as tensors with <span>(sge frac{1}{2} N)</span> indices. Only in critical dimensions there are states with <span>(sle frac{1}{2} N)</span>. Looking at the explicit coefficients of the combinations needed to make the irreps from the lightcone states we trace the origin of the chaotic behavior of certain cubic amplitudes considered in literature to the extremely precise and sensitive mixtures of states. For example the vectors at level <span>(N=19)</span> are a linear combinations of states and when the coefficients are normalized to be integer some of them have more than 1200 figures.\u0000</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"85 4","pages":""},"PeriodicalIF":4.2,"publicationDate":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-025-13955-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143749129","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":"The study of high-efficiency pion production","authors":"Weichao Yao,&nbsp;Masaharu Aoki,&nbsp;Chen Wu,&nbsp;Kou Oishi,&nbsp;Yoshinori Fukao","doi":"10.1140/epjp/s13360-025-06164-9","DOIUrl":"10.1140/epjp/s13360-025-06164-9","url":null,"abstract":"<div><p>An optimization study was conducted on low-energy pion production using a cylindrical tungsten target for the COMET Phase-II experiment, taking into account recent measurements of proton-beam emittance. The study suggests factor 1.6 of improvement in pion production efficiency by reducing the target radius down to 4 mm. This enhancement is attributed to the reduction in the emittance of the proton beam. Further increases in target radius simply reduce the yield of low-energy pions and, consequently, the stopping rate of low-energy muons in the muon stopping target. The analysis reveals that the pion production spectrum at higher momentum cannot compensate for the limitations imposed by the range–momentum curve of pions. There is a potential further improvement in low-energy pion production with an ideally narrow proton beam.</p></div>","PeriodicalId":792,"journal":{"name":"The European Physical Journal Plus","volume":"140 4","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjp/s13360-025-06164-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143749122","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}