物理与天体物理最新文献

{"title":"Optimization of Terahertz Radiation Generation via Sech-Shaped Laser Pulses in Collisional Homogenous Plasma","authors":"Jasveer Singh,&nbsp;Sunita Rani,&nbsp;Hitesh Kumar Midha,&nbsp;Vivek Sharma,&nbsp;Vishal Thakur","doi":"10.1007/s13538-025-01774-1","DOIUrl":"10.1007/s13538-025-01774-1","url":null,"abstract":"<div><p>The influence of the sech-shaped laser pulse and collisional plasma profile on the efficacy of terahertz (THz) production has been thoroughly investigated. The study assesses the impact of the sech parameter (b) on THz production, revealing that an increase in b results in a more focused laser pulse, hence augmenting plasma interaction and raising THz generation efficiency. The examination of transverse distance indicates that increased values of b lead to a more concentrated ideal region for THz production, with peak efficiency relocating to reduced transverse distances. The impact of collisional frequency is analysed, revealing that elevated collisional frequencies diminish THz generating efficiency owing to heightened dispersion and energy dissipation. Moreover, plasma density has a direct correlation with THz production, since elevated density promotes intensified nonlinear interactions and improved efficiency. These findings highlight the need of optimising these parameters for efficient THz production.</p></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"55 4","pages":""},"PeriodicalIF":1.5,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143875448","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":"Rational solutions of nonautonomous quadrilateral equations by the bilinearization of Bäcklund transformation systems","authors":"Danda Zhang,&nbsp;Liya Zhu,&nbsp;Yingying Sun","doi":"10.1134/S0040577925040051","DOIUrl":"10.1134/S0040577925040051","url":null,"abstract":"<p> Rational solutions of several nonautonomous quadrilateral equations in the ABS and ABS* list are obtained in a neat form of Casoratians, which mostly relies on a single <span>(tau)</span> function. The corresponding nonautonomous bilinear equations are listed in difference and differential–difference forms by introducing an auxiliary variable. Instead of bilinearizing quadrilateral equations, we present their related Bäcklund transformation systems, which directly reduce to bilinear equations by specific transformations. As an application, a result related to the discrete Painlevé equation is given. </p>","PeriodicalId":797,"journal":{"name":"Theoretical and Mathematical Physics","volume":"223 1","pages":"576 - 596"},"PeriodicalIF":1.0,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143875267","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":"Integration of the generalized Camassa–Holm equation in the class of periodic functions","authors":"B. A. Babajanov,&nbsp;D. O. Atajonov","doi":"10.1134/S0040577925040075","DOIUrl":"10.1134/S0040577925040075","url":null,"abstract":"<p> We study periodic solutions of the generalized Camassa–Holm equation (CH-<span>(gamma)</span> equation). We show that the generalized CH-<span>(gamma)</span> equation is also an important theoretical model because it is a completely integrable system. We obtain representation for periodic solutions of the generalized CH-<span>(gamma)</span> equation in the framework of the inverse spectral problem for a weighted Sturm–Liouville operator. </p>","PeriodicalId":797,"journal":{"name":"Theoretical and Mathematical Physics","volume":"223 1","pages":"624 - 635"},"PeriodicalIF":1.0,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143875424","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":"Stepping up superradiance constraints on axions","authors":"Samuel J. Witte, Andrew Mummery","doi":"10.1103/physrevd.111.083044","DOIUrl":"https://doi.org/10.1103/physrevd.111.083044","url":null,"abstract":"Light feebly-coupled bosonic particles can efficiently extract the rotational energy of rapidly spinning black holes on subastrophysical timescales via a phenomenon known as black hole superradiance. In the case of light axions, the feeble self-interactions of these particles can lead to a nonlinear coupled evolution of many superradiant quasibound states, dramatically altering the rate at which the black hole is spun down. In this work, we extend the study of axion superradiance to higher order states, solving for the first time the coupled evolution of all states with n</a:mi>≤</a:mo>5</a:mn></a:math> in the fully relativistic limit (with <c:math xmlns:c=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><c:mi>n</c:mi></c:math> being the principal quantum number). Using a Bayesian framework, we rederive constraints on axions using the inferred spins of solar mass black holes, demonstrating that previously adopted limit-setting procedures have underestimated current sensitivity to the axion decay constant <e:math xmlns:e=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><e:msub><e:mi>f</e:mi><e:mi>a</e:mi></e:msub></e:math> by around 1 order of magnitude and that the inclusion to higher order states allows one to reasonably capture the evolution of typical high-spin black holes across a much wider range of parameter space, thereby allowing constraints to be extended to more massive axions. We conclude with an extensive discussion on the systematics associated with spin inference from x-ray observations. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20167,"journal":{"name":"Physical Review D","volume":"130 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143876064","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Gravitational form factor D of charmonium from shear stress","authors":"Tianyang Hu, Xianghui Cao, Siqi Xu, Yang Li, Xingbo Zhao, James P. Vary","doi":"10.1103/physrevd.111.074031","DOIUrl":"https://doi.org/10.1103/physrevd.111.074031","url":null,"abstract":"Based on our recent analysis of the hadronic matrix element of the stress-energy tensor in covariant light-front dynamics, we extract the charmonium gravitational form factor D</a:mi>(</a:mo>Q</a:mi>2</a:mn></a:msup>)</a:mo></a:math> from shear stress <e:math xmlns:e=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><e:msup><e:mi>T</e:mi><e:mn>12</e:mn></e:msup></e:math>. This is in contrast to our recent work using the (light-front) energy density <g:math xmlns:g=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><g:msup><g:mi>T</g:mi><g:mrow><g:mo>+</g:mo><g:mo>−</g:mo></g:mrow></g:msup></g:math>. Indeed, by comparing these two currents, we identify terms that are responsible for the violation of the current conservation. Numerical results based on basis light-front quantization show that the violation effects are small, and the <i:math xmlns:i=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><i:mi>D</i:mi></i:math> term extracted from the two currents are close to each other, hence validating our previous work using <k:math xmlns:k=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><k:msup><k:mi>T</k:mi><k:mrow><k:mo>+</k:mo><k:mo>−</k:mo></k:mrow></k:msup></k:math>. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20167,"journal":{"name":"Physical Review D","volume":"44 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143876090","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"From filament to clumps and cores","authors":"Han-Tsung Lee, Ya-Wen Tang, Patrick M. Koch, Jia-Wei Wang, Seamus Clarke, Gary A. Fuller, Nicolas Peretto, Won-Ju Kim, Hsi-Wei Yen","doi":"10.1051/0004-6361/202452974","DOIUrl":"https://doi.org/10.1051/0004-6361/202452974","url":null,"abstract":"<i>Aims.<i/> Fragmentation is a multiscale process forming structures with sizes that vary by several orders of magnitude. However, multiscale investigations of the magnetic field characterizing its properties across the physical scales relevant to the fragmentation process (filaments and clouds, clumps, and cores) are elusive. In this work, we present a multiscale study of the magnetic field using polarization continuum observations with various resolutions.<i>Methods.<i/> We made use of data from the JCMT and the SMA at 850 μm and 1.3 millimeter (mm) wavelengths to study the filamentary infrared dark cloud SDC18.624-0.070. Our observations cover filament (~ 10 pc), filament-embedded clump (~ 1 pc), isolated clump (~ 0.1 pc), and clump-embedded core (~ 0.01) scales, which are key to investigating the impact of the magnetic field on fragmentation.<i>Results.<i/> We found a magnetic field that is predominantly perpendicular to the major axes of all structures (filament, clumps, and cores). While its circular mean orientations are preserved within about 20°, a systematically increasing field dispersion toward smaller scales indicates the growing impact of gravity. Velocity gradients traced by N<sub>2<sub/>H<sup>+<sup/>, with a resolution similar to that of the polarization observations, also tend to be perpendicular to the filament’s major axis. All these features suggest that the magnetic field constrains the direction of accretion and initial contraction, as predicted by strong-field models.<i>Conclusions.<i/> We argue that the observed magnetic field and velocity gradient can result from a combination of converging flows, based on a detected SiO component along the filament, and rotation, based on the measured N<sub>2<sub/>H<sup>+<sup/> specific angular momentum profile. A multiscale energy analysis of gravity, magnetic field, and turbulence quantifying their relative importance shows that SDC18-S, despite displaying less fragmentation, has a larger field strength than SDC18-N, which harbors more fragments. A faster (SDC18-N) and slower evolution (SDC18-S) to a gravity-dominated regime has been found to explain the different fragmentation at clump-embedded core scale, with the stronger magnetic field in SDC18-S suppressing fragmentation to a greater extent.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"37 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143880664","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Quantifying jet–interstellar medium interactions in Cyg X-1: Insights from dual-frequency bow shock detection with MeerKAT","authors":"P. Atri, S. E. Motta, J. van den Eijnden, J. H. Matthews, J. C. A. Miller-Jones, R. Fender, D. Williams-Baldwin, I. Heywood, P. Woudt","doi":"10.1051/0004-6361/202452837","DOIUrl":"https://doi.org/10.1051/0004-6361/202452837","url":null,"abstract":"<i>Context.<i/> Accretion and outflows are astrophysical phenomena observed across a wide range of objects, from white dwarfs to supermassive black holes. Developing a complete picture of these processes requires complementary studies across this full spectrum of jet-launching sources. Jet–interstellar medium (ISM) interaction sites near black hole X-ray binaries provide unique laboratories that provide insights into the energetics of the jets launched from stellar-mass black holes.<i>Aims.<i/> This work aims to detect and characterise the bow shock near one black hole X-ray binary, Cyg X-1, and then use this bow shock structure to parametrise the properties of the jet launched by Cyg X-1 over its lifetime.<i>Methods.<i/> We used the MeerKAT radio telescope to investigate the bow shock structure formed by the interaction between the jets of Cyg X-1 and the ISM. Using new <i>L<i/>- and <i>S<i/>-band detections of the bow shock, we constrained the density of the unshocked ISM and mapped the bow shock’s spectral index. These values were applied to self-similar models developed initially for FR II galaxies to estimate the energy transport rate and the age of Cyg X-1 jets.<i>Results.<i/> We successfully detect the bow shock north of Cyg X-1 in the <i>L<i/> and <i>S<i/> bands and report its size and brightness. We present the spectral index distribution across the bow shock, which is in the range −0.9 ≤ <i>α<i/> ≤ 0.4, with an error distribution (0.6 ≤ Δ<i>α<i/> ≤ 1.5) that peaks at unity. We determine that the unshocked ISM density is 6–7 cm<sup>−3<sup/> for a temperature range of 10<sup>4<sup/>–3 × 10<sup>6<sup/> K. This temperature range suggests that the velocity of the bow shock is 21 km s km s<sup>−1<sup/>. The age of the Cyg X-1 jet responsible for the bow shock is 0.04–0.3 Myr, and the power of the jet is constrained to 2 × 10<sup>31<sup/> ergs s ergs s<sup>−1<sup/> for the case of opening angles of 0.3°–2.0°. We also detect new morphological features of the bow shock in the <i>S<i/>-band image. The comparison of archival H<sub><i>α<i/><sub/> maps with the new radio observations hints at different regions of emission, different temperature ranges, and different ISM densities.<i>Conclusions.<i/> MeerKAT’s sensitivity and resolution effectively reveal low surface brightness features of the Cyg X-1 bow shock. The spectral index suggests a consistent emission origin across the structure. The ISM density around Cyg X-1 is on the higher end for Galactic environments, and our results indicate a lower jet energy transport rate than prior estimates. Further searches with MeerKAT will help build a statistically significant sample, advancing our understanding of black hole X-ray binary jets and their impact on their local environments.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"108 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143880665","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Do accretion-powered stellar winds help spin down T Tauri stars?","authors":"Lukas Gehrig, Eric Gaidos, Laura Venuti, Ann Marie Cody, Neal J. Turner","doi":"10.1051/0004-6361/202553730","DOIUrl":"https://doi.org/10.1051/0004-6361/202553730","url":null,"abstract":"How T Tauri stars remain slowly rotating while still accreting material is a long-standing puzzle. Current models suggest that these stars may lose angular momentum through magnetospheric ejections (MEs) of disk material and accretion-powered stellar winds (APSWs). The individual contribution of each mechanism to the stellar spin evolution, however, is also unclear. We explore how these two scenarios could be distinguished by applying stellar spin models to near-term observations. We produced synthetic stellar populations of accreting Class II stars with spreads in the parameters governing the spin-down processes and find that an APSW strongly affects the ratio of the disk truncation radius to the co-rotation radius, ℛ = <i>R<i/><sub>t<sub/>/<i>R<i/><sub>co<sub/>. The ME and APSW scenarios are distinguished to a high degree of confidence when at least <i>N<i/><sub>crit<sub/> ≳ 250 stars have values measured for ℛ. Newly developed light curve analysis methods enable the measuring of ℛ for enough stars to distinguish the spin-down scenarios and will be important in the course of upcoming observing campaigns.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"32 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143880669","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Revisiting inelastic Cu + H collisions and the non-LTE Galactic evolution of copper","authors":"S. Caliskan, A. M. Amarsi, M. Racca, I. Koutsouridou, P. S. Barklem, K. Lind, S. Salvadori","doi":"10.1051/0004-6361/202554251","DOIUrl":"https://doi.org/10.1051/0004-6361/202554251","url":null,"abstract":"The Galactic evolution of copper remains poorly understood, partly due to the strong departures from local thermodynamic equilibrium (LTE) affecting Cu I lines. A key source of uncertainty in non-LTE modelling is the treatment of inelastic Cu + H collisions. We present new rate coefficients based on a combined asymptotic LCAO (linear combination of atomic orbitals) and free electron model approach, which show significant differences from previous calculations. Applying these updated rates to non-LTE stellar modelling, we find reduced line-to-line scatter and improved consistency between metal-poor dwarfs and giants. Our non-LTE analysis reveals a strong upturn in the [Cu/Fe] trend towards lower [Fe/H] < −1.7. We show that this may reflect the interplay between external enrichment of Cu-rich material of the Milky Way halo at low metallicities, and metallicity-dependent Cu yields from rapidly rotating massive stars. This highlights the unique diagnostic potential of accurate Cu abundances for understanding both stellar and Galactic evolution.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"100 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143880708","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Double progenitor origin of the S-star cluster","authors":"Sill Verberne, Elena Maria Rossi, Sergey E. Koposov, Zephyr Penoyre, Manuel Cavieres, Konrad Kuijken","doi":"10.1051/0004-6361/202554247","DOIUrl":"https://doi.org/10.1051/0004-6361/202554247","url":null,"abstract":"The origin of the cluster of S-stars located in the Galactic Centre is tied to the supermassive black hole Sagittarius A*, but exactly how is still debated. In this paper, we investigate whether the Hills mechanism can simultaneously reproduce both the S-star cluster’s properties and the observed number of hypervelocity stars. To do so, we forward-modelled the capture and disruption of binary stars originating from the nuclear star cluster (NSC) and the clockwise disc (CWD). We find that the ratio of evolved to main-sequence S-stars is highly sensitive to the origin of the binaries, and that neither the injection of binaries from the CWD nor from the NSC exclusively can reproduce all observations. However, when considering the injection of binaries from both locations, we are able to reproduce all the observations simultaneously, including the number of observed hypervelocity stars, the evolutionary stage of the S-stars, their luminosity function, and the distribution of their semi-major axes. The implications of our findings include that ∼90% of hypervelocity stars ejected over the past ∼10 Myr should originate from the CWD, that the main-sequence S-stars originated in the CWD, and that the evolved S-stars originated in an old stellar population such as the NSC.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"53 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143880709","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}