A microscopic understanding of the complex solute-defect interaction is pivotal for optimizing the alloy’s macroscopic mechanical properties.Simulating solute segregation in a plastically deformed crystalline system ...A microscopic understanding of the complex solute-defect interaction is pivotal for optimizing the alloy’s macroscopic mechanical properties.Simulating solute segregation in a plastically deformed crystalline system at atomic resolution remains challenging.The objective is to efficiently model and predict a phys-ically informed segregated solute distribution rather than simulating a series of diffusion kinetics.To ad-dress this objective,we coupled molecular dynamics(MD)and Monte Carlo(MC)methods using a novel method based on virtual atoms technique.We applied our MD-MC coupling approach to model off-lattice carbon(C)solute segregation in nanoindented Fe-C samples containing complex dislocation networks.Our coupling framework yielded the final configuration through efficient parallelization and localized en-ergy computations,showing C Cottrell atmospheres near dislocations.Different initial C concentrations resulted in a consistent trend of C atoms migrating from less crystalline distortion to high crystalline distortion regions.Besides unraveling the strong spatial correlation between local C concentration and defect regions,our results revealed two crucial aspects of solute segregation preferences:(1)defect ener-getics hierarchy and(2)tensile strain fields near dislocations.The proposed approach is generic and can be applied to other material systems as well.展开更多
We review recent experimental and theoretical results for the electromagnetic form factors of hyperons(Y)in the timelike region,accessible in the reactions e^(+)e^(-)→YY.Specifically,we focus on the final statesΛΛ...We review recent experimental and theoretical results for the electromagnetic form factors of hyperons(Y)in the timelike region,accessible in the reactions e^(+)e^(-)→YY.Specifically,we focus on the final statesΛΛ,ΛΣ^(0)/Λ,Σ^(0)Λ,■■,andΩΩ.TheΛ_(c)Λ_(c)system is also discussed.展开更多
Interlayer interactions in bilayer or multilayer electron systems have been studied extensively,and many exotic physical phenomena have been revealed.However,systematic investigations of the impact of interlayer inter...Interlayer interactions in bilayer or multilayer electron systems have been studied extensively,and many exotic physical phenomena have been revealed.However,systematic investigations of the impact of interlayer interactions on magnonic physics are very few.Here,we use a van derWaals(vdW)honeycomb heterostructure as a platform to investigate the modulation of magnon properties in honeycomb AA-and AB-stacking heterostructures with ferromagnetic and antiferromagnetic interlayer interactions,including topological phases and thermal Hall conductivity.Our results reveal that interlayer interactions play a crucial role in modulating the magnonic topology and Hall transport properties of magnetic heterostructures,with potential for experimental realization.展开更多
We present a detailed analysis of the set theoretical proof of Wigner for Bell type inequalities with the following result. Wigner introduced a crucial assumption that is not related to Einstein’s local realism, but ...We present a detailed analysis of the set theoretical proof of Wigner for Bell type inequalities with the following result. Wigner introduced a crucial assumption that is not related to Einstein’s local realism, but instead, without justification, to the existence of certain joint probability measures for possible and actual measurement outcomes of Einstein-Podolsky-Rosen (EPR) experiments. His conclusions about Einstein’s local realism are, therefore, not applicable to EPR experiments and the contradiction of the experimental outcomes to Wigner’s results has no bearing on the validity of Einstein’s local realism.展开更多
Many applications in computational science and engineering require the computation of eigenvalues and vectors of dense symmetric or Hermitian matrices. For example, in DFT （density functional theory） calculations on...Many applications in computational science and engineering require the computation of eigenvalues and vectors of dense symmetric or Hermitian matrices. For example, in DFT （density functional theory） calculations on modern supercomputers 10% to 30% of the eigenvalues and eigenvectors of huge dense matrices have to be calculated. Therefore, performance and parallel scaling of the used eigensolvers is of upmost interest. In this article different routines of the linear algebra packages ScaLAPACK and Elemental for parallel solution of the symmetric eigenvalue problem are compared concerning their performance on the BlueGene/P supercomputer. Parameters for performance optimization are adjusted for the different data distribution methods used in the two libraries. It is found that for all test cases the new library Elemental which uses a two-dimensional element by element distribution of the matrices to the processors shows better performance than the old ScaLAPACK library which uses a block-cyclic distribution.展开更多
In 2021,the Belle collaboration reported the first observation of a new structure in theψ(2S)γfinal state produced in the two-photon fusion process.In the hadronic molecule picture,this new structure can be associat...In 2021,the Belle collaboration reported the first observation of a new structure in theψ(2S)γfinal state produced in the two-photon fusion process.In the hadronic molecule picture,this new structure can be associatedwith the shallow isoscalar D*D* bound state and as such is an excellent candidate for the spin-2 partner of the X(3872)with the quantum numbers J^(PC)=2^(++)conventionally named X_(2).展开更多
Sunlight-like lasers that have a continuous broad frequency spectrum,random phase spectrum,and random polarization are formulated theoretically.With a sunlight-like laser beam consisting of a sequence of temporal spec...Sunlight-like lasers that have a continuous broad frequency spectrum,random phase spectrum,and random polarization are formulated theoretically.With a sunlight-like laser beam consisting of a sequence of temporal speckles,the resonant three-wave coupling that underlies parametric instabilities in laser–plasma interactions can be greatly degraded owing to the limited duration of each speckle and the frequency shift between two adjacent speckles.The wave coupling can be further weakened by the random polarization of such beams.Numerical simulations demonstrate that the intensity threshold of stimulated Raman scattering in homogeneous plasmas can be doubled by using a sunlight-like laser beam with a relative bandwidth of∼1%as compared with a monochromatic laser beam.Consequently,the hot-electron generation harmful to inertial confinement fusion can be effectively controlled by using sunlight-like laser drivers.Such drivers may be realized in the next generation of broadband lasers by combining two or more broadband beams with independent phase spectra or by applying polarization smoothing to a single broadband beam.展开更多
Campus security has aroused many concerns from the whole society.Stampede is one of the most frequent and influential accidents in campus.Studies on pedestrian dynamics especially focusing on students are essential fo...Campus security has aroused many concerns from the whole society.Stampede is one of the most frequent and influential accidents in campus.Studies on pedestrian dynamics especially focusing on students are essential for campus security,which are helpful to improve facility design and emergency evacuation strategy.In this paper,primary and middle school students were recruited to participate in the single-file experiments.The microscopic movement characteristics,including walking speed,headway,gait characteristics(step length,step frequency and swaying amplitude)and their relations were investigated.Age and gender differences in the headway-speed diagram and space requirements were analyzed by statistical tests.The results indicated that the impacts of age and gender were significant.There were three stages for the influence of gender on the headway-speed diagram for both age groups.The impacts on students'space requirements were consistent for different age and gender groups.But the impacts of age and gender on free-flow speed were affected by each other.Due to the connection of walking speed and gait characteristics,the comparisons of gait characteristics between different ages and genders were performed to understand the corresponding differences in speed more deeply.The results showed that differences in step length and swaying amplitude between males and females were significant for both age groups.The effect of gender on step frequency was significant for primary students.But for middle school students,whether gender had significant impact on step frequency was not clear here because of the large P-value.Besides,the influence of age on gait characteristics changed with gender.展开更多
We study prompt hadroproduction of the charged bottomonium-like states Zb± （10610） and Zb±（10650）, and the charged eharmonium-like states Zc± （3900） and Zc± （4020）, at the Tevatron and the ...We study prompt hadroproduction of the charged bottomonium-like states Zb± （10610） and Zb±（10650）, and the charged eharmonium-like states Zc± （3900） and Zc± （4020）, at the Tevatron and the LHC, provided that these states are S-wave hadronic molecules. Using two Monte Carlo event generators, Herwig and Pythia, to simulate the production of heavy meson pairs, we derive an order-of-magnitude estimate of the production rates for these four particles. Our estimates yield a cross section at the nb level for the Zb（10610） and Zb（10650）. The results for the Zc（3900） and Zc （4020） are larger by a factor of 2~30. These cross sections are large enough to be observed, and measurements at hadron colliders in the future will supplement the study using electron-positron collisions, and therefore allow to explore the mysterious nature of these exotic states.展开更多
Counterfactual definiteness must be used as at least one of the postulates or axioms that are necessary to derive Bell-type inequalities. It is considered by many to be a postulate that not only is commensurate with c...Counterfactual definiteness must be used as at least one of the postulates or axioms that are necessary to derive Bell-type inequalities. It is considered by many to be a postulate that not only is commensurate with classical physics (as for example Einstein’s special relativity), but also separates and distinguishes classical physics from quantum mechanics. It is the purpose of this paper to show that Bell’s choice of mathematical functions and independent variables implicitly includes counterfactual definiteness. However, his particular choice of variables reduces the generality of his theory, as well as the physics of all Bell-type theories, so significantly that no meaningful comparison of these theories with actual Einstein-Podolsky-Rosen experiments can be made.展开更多
In this paper we propose a dispersive method to describe two-body scattering with unitarity imposed.This approach is applied to elasticππscattering.The amplitudes keep single-channel unitarity and describe the exper...In this paper we propose a dispersive method to describe two-body scattering with unitarity imposed.This approach is applied to elasticππscattering.The amplitudes keep single-channel unitarity and describe the experimental data well,and the low-energy amplitudes are consistent with that of chiral perturbation theory.The pole locations of theσ,f0(980),ρ(770)and f_(2)(1270)and their couplings toππare obtained.A virtual state appearing in the isospin-two S-wave is confirmed.The correlations between the left(and right)hand cut and the poles are discussed.Our results show that the poles are more sensitive to the right hand cut rather than the left hand cut.The proposed method could be used to study other two-body scattering processes.展开更多
Machine learning has become a premier tool in physics and other fields of science.It has been shown that the quantum mechanical scattering problem cannot only be solved with such techniques,but it was argued that the ...Machine learning has become a premier tool in physics and other fields of science.It has been shown that the quantum mechanical scattering problem cannot only be solved with such techniques,but it was argued that the underlying neural network develops the Bom series for shallow potentials.However,classical machine learning algorithms fail in the unitary limit of an infinite scattering length.The unitary limit plays an important role in our understanding of bound strongly interacting fermionic systems and can be realized in cold atom experiments.Here,we develop a formalism that explains the unitary limit in terms of what we define as unitary limit surfaces.This not only allows to investigate the unitary limit geometrically in potential space,but also provides a numerically simple approach towards unnaturally large scattering lengths with standard multilayer perceptrons.Its scope is therefore not limited to applications in nuclear and atomic physics,but includes all systems that exhibit an unnaturally large scale.展开更多
We calculate the energy levels corresponding to the Roper resonance based on a two-flavor chiral effective Lagrangian for pions,nucleons,deltas,and the Roper resonance at the leading one-loop order.We show that the Ro...We calculate the energy levels corresponding to the Roper resonance based on a two-flavor chiral effective Lagrangian for pions,nucleons,deltas,and the Roper resonance at the leading one-loop order.We show that the Roper mass can be extracted from these levels for lattice volumes of moderate size.展开更多
based on our analysis of the contributions from the connected and disconnected contraction diagrams to the pion-kaon scattering amplitude,we provide the first determination of the only free low-energy constant at O(p^...based on our analysis of the contributions from the connected and disconnected contraction diagrams to the pion-kaon scattering amplitude,we provide the first determination of the only free low-energy constant at O(p^(4)),known as L_(0)^(r),in SU(4|1)Partially-Quenched Chiral Perturbation theory using the data from the Extended Twisted Mass collaboration,L_(0)^(r)(μ=M_(ρ))=0.77(20)(25)(7)(7)(2)·10^(-3).The theory uncertainties originate from the unphysical scattering length,the physical low-energy constants,the higher-order chiral corrections,the(lattice)meson masses and the pion decay constant,respectively.展开更多
The internal structure of the charm-strange mesons D_(s0)^(*)(2317)and D_(s1)(2460)are the subject of intensive studies.Their widths are small because they decay dominantly through isospinbreaking hadronic channels D_...The internal structure of the charm-strange mesons D_(s0)^(*)(2317)and D_(s1)(2460)are the subject of intensive studies.Their widths are small because they decay dominantly through isospinbreaking hadronic channels D_(s0)^(*)(2317)^(+)→D_(s)^(+)π^(0) and D _(s1)(2460)^(+)→D_(s)^(*+)π^(0).The D_(s1)(2460)can also decay into the hadronic final states D_(s)^(+)ππ,conserving isospin.In that case there is,however,a strong suppression from phase space.We study the transition D_(s1)(2460)^(+)→D_(s)^(+)π^(+)π^(-)in the scenario that the D_(s1)(2460)is a D^(*)K hadronic molecule.The ππ final state interaction is taken into account through dispersion relations.We find that the ratio of the partial widths of the Γ(D_(s1)(2460)^(+)→D_(s)^(+)π^(+)π^(-)) / Γ(D_(s1)(2460)^(+)→D_(s)^(*+)π^(0))obtained in the molecular picture is consistent with the existing experimental measurement.More interestingly,we demonstrate that theπ+π−invariant mass distribution shows a double bump structure,which can be used to disentangle the hadronic molecular picture from the compact state picture for the D_(s1)(2460)^(+).Predictions on the B_(s1)^(0)→B_(s)^(0)π^(+)π^(-)are also made.展开更多
Broadband lasers have been proposed as future drivers of inertial confined fusion(ICF)to enhance the laser-target coupling efficiency via the mitigation of various parametric instabilities.The physical mechanisms invo...Broadband lasers have been proposed as future drivers of inertial confined fusion(ICF)to enhance the laser-target coupling efficiency via the mitigation of various parametric instabilities.The physical mechanisms involved have been explored recently,but are not yet fully understood.Here,stimulated Raman scattering(SRS)as one of the key parametric instabilities is investigated theoretically and numerically for a broadband laser propagating in homogeneous plasma in multidimensional geometry.The linear SRS growth rate is derived as a function of scattering angles for two monochromatic laser beams with a fixed frequency differenceδω.Ifδω/ω_(0)∼1%,withω0 the laser frequency,these two laser beams may be decoupled in stimulating backward SRS while remaining coupled for sideward SRS at the laser intensities typical for ICF.Consequently,side-scattering may dominate over backward SRS for two-color laser light.This finding of SRS transition from backward to sideward SRS is then generalized for a broadband laser with a few-percent bandwidth.Particle-in-cell simulations demonstrate that with increasing laser bandwidth,the sideward SRS gradually becomes dominant over the backward SRS.Since sideward SRS is very efficient in producing harmful hot electrons,attention needs to be paid on this effect if ultra-broadband lasers are considered as next-generation ICF drivers.展开更多
Quantum electrodynamics is often considered to be a trivial theory.This is based on a number of evidences,both numerical and analytical.One of the strong indications for triviality of QED is the existence of the Landa...Quantum electrodynamics is often considered to be a trivial theory.This is based on a number of evidences,both numerical and analytical.One of the strong indications for triviality of QED is the existence of the Landau pole for the running coupling.We show that by treating QED as the leading order approximation of an effective field theory and including the next-to-leading order corrections,the Landau pole is removed.We also analyze the cutoff dependence of the bare coupling at two-loop order and conclude that the conjecture,that for reasons of self-consistency,QED needs to be trivial is a mere artefact of the leading order approximation to the corresponding effective field theory.展开更多
We discuss the X(5568)particle recently announced by the D0 Collaboration.Several types of models were proposed to explain this structure in the literature.As pointed out by Burns and Swanson(ar Xiv:1603.04366),none o...We discuss the X(5568)particle recently announced by the D0 Collaboration.Several types of models were proposed to explain this structure in the literature.As pointed out by Burns and Swanson(ar Xiv:1603.04366),none of them provides a satisfactory description of the observation.We provide additional arguments using general properties of QCD,and conclude that the observation of the X(5568),if confirmed,poses serious challenges to our understanding of nonperturbative QCD.展开更多
The Wilsonian renormalization group approach to the Lippmann-Schwinger equation with a multitude of cutoff parameters is introduced.A system of integro-differential equations for the cutoff-dependent potential is obta...The Wilsonian renormalization group approach to the Lippmann-Schwinger equation with a multitude of cutoff parameters is introduced.A system of integro-differential equations for the cutoff-dependent potential is obtained.As an illustration,a perturbative solution of these equations with two cutoff parameters for a simple case of an S-wave low-energy potential in the form of a Taylor series in momenta is obtained.The relevance of the obtained results for the effective field theory approach to nucleon-nucleon scattering is discussed.展开更多
Magicity,or shell closure,plays an important role in our understanding of complex nuclear phenomena.In this work,we employ one of the state-of-the-art density functional theories,the deformed relativistic Hartree-Bogo...Magicity,or shell closure,plays an important role in our understanding of complex nuclear phenomena.In this work,we employ one of the state-of-the-art density functional theories,the deformed relativistic Hartree-Bogoliubov theory in continuum(DRHBc)with the density functional PC-PK1,to investigate the evolution of the N=20,28,50 shell closures in the 20≤Z≤30 region.We show how these three conventional shell closures evolve from the proton drip line to the neutron drip line by studying the charge radii,two-neutron separation energies,two-neutron gaps,quadrupole deformations,and single-particle levels.In particular,we find that in the 21≤Z≤27 region,the N=50 shell closure disappears or becomes quenched,mainly due to the deformation effects.Similarly,both experimental data and theoretical predictions indicate that the N=28 shell closure disappears in the Mn isotopic chain,mainly due to the deformation effects.The DRHBc theory predicts the existence of the N=20 shell closure in the Ca,Sc,and Ti isotopic chains,but the existing data for the Ti isotopes suggest the contrary,and therefore further research is needed.展开更多
基金the funding from the Ger-man Research Foundation(DFG)-BE 5360/1-1 and ThyssenKrupp Europe.
文摘A microscopic understanding of the complex solute-defect interaction is pivotal for optimizing the alloy’s macroscopic mechanical properties.Simulating solute segregation in a plastically deformed crystalline system at atomic resolution remains challenging.The objective is to efficiently model and predict a phys-ically informed segregated solute distribution rather than simulating a series of diffusion kinetics.To ad-dress this objective,we coupled molecular dynamics(MD)and Monte Carlo(MC)methods using a novel method based on virtual atoms technique.We applied our MD-MC coupling approach to model off-lattice carbon(C)solute segregation in nanoindented Fe-C samples containing complex dislocation networks.Our coupling framework yielded the final configuration through efficient parallelization and localized en-ergy computations,showing C Cottrell atmospheres near dislocations.Different initial C concentrations resulted in a consistent trend of C atoms migrating from less crystalline distortion to high crystalline distortion regions.Besides unraveling the strong spatial correlation between local C concentration and defect regions,our results revealed two crucial aspects of solute segregation preferences:(1)defect ener-getics hierarchy and(2)tensile strain fields near dislocations.The proposed approach is generic and can be applied to other material systems as well.
基金the support from the National Natural Science Foundation of China(NSFC)under Grant Nos.12322502 and 12335002the Joint Large Scale Scientific Facility Funds of the NSFC and Chinese Academy of Sciences(CAS)under Contract No.U1932110+3 种基金the Hunan Provincial Natural Science Foundation under Grant No.2024JJ3004the Fundamental Research Funds for the central universitiessupported by the CAS President’s International Fellowship Initiative(PIFI)(Grant No.2025PD0022)by the MKW NRW under the funding code No.NW21-024-A and by ERC AdG EXOTIC(Grant No.101018170)。
文摘We review recent experimental and theoretical results for the electromagnetic form factors of hyperons(Y)in the timelike region,accessible in the reactions e^(+)e^(-)→YY.Specifically,we focus on the final statesΛΛ,ΛΣ^(0)/Λ,Σ^(0)Λ,■■,andΩΩ.TheΛ_(c)Λ_(c)system is also discussed.
基金supported by the National Natural Science Foundation of China(Grant Nos.12404051,12347156,12174157,12074150,and 12174158)the National Key Research and Development Program of China(Grant No.2022YFA1405200)+2 种基金the Natural Science Foundation of Jiangsu Province(Grant No.BK20230516)the Scientific Research Project of Jiangsu University(Grant No.550171001)support provided by the Deutsche Forschungsgemeinschaft(DFG,German Research Founda-tion)-TRR 288/2-422213477(project B06).
文摘Interlayer interactions in bilayer or multilayer electron systems have been studied extensively,and many exotic physical phenomena have been revealed.However,systematic investigations of the impact of interlayer interactions on magnonic physics are very few.Here,we use a van derWaals(vdW)honeycomb heterostructure as a platform to investigate the modulation of magnon properties in honeycomb AA-and AB-stacking heterostructures with ferromagnetic and antiferromagnetic interlayer interactions,including topological phases and thermal Hall conductivity.Our results reveal that interlayer interactions play a crucial role in modulating the magnonic topology and Hall transport properties of magnetic heterostructures,with potential for experimental realization.
文摘We present a detailed analysis of the set theoretical proof of Wigner for Bell type inequalities with the following result. Wigner introduced a crucial assumption that is not related to Einstein’s local realism, but instead, without justification, to the existence of certain joint probability measures for possible and actual measurement outcomes of Einstein-Podolsky-Rosen (EPR) experiments. His conclusions about Einstein’s local realism are, therefore, not applicable to EPR experiments and the contradiction of the experimental outcomes to Wigner’s results has no bearing on the validity of Einstein’s local realism.
文摘Many applications in computational science and engineering require the computation of eigenvalues and vectors of dense symmetric or Hermitian matrices. For example, in DFT （density functional theory） calculations on modern supercomputers 10% to 30% of the eigenvalues and eigenvectors of huge dense matrices have to be calculated. Therefore, performance and parallel scaling of the used eigensolvers is of upmost interest. In this article different routines of the linear algebra packages ScaLAPACK and Elemental for parallel solution of the symmetric eigenvalue problem are compared concerning their performance on the BlueGene/P supercomputer. Parameters for performance optimization are adjusted for the different data distribution methods used in the two libraries. It is found that for all test cases the new library Elemental which uses a two-dimensional element by element distribution of the matrices to the processors shows better performance than the old ScaLAPACK library which uses a block-cyclic distribution.
基金supported in part by the National Natural Science Foundation of China(Grant Nos.12070131001,12125507,11835015,and 12047503)the Deutsche Forschungsgemeinschaft(DFG)through the funds provided to the Sino-German Collaborative Research Center TRR110“Symmetries and the Emergence of Structure in QCD”(Project-ID 196253076)+4 种基金the Chinese Academy of Sciences(CAS)(Grant Nos.YSBR-101 and XDB34030000)the EU STRONG-2020 project under the program H2020-INFRAIA-2018-1(Grant No.824093)the Generalitat valenciana(GVA)for the project with ref.CIDEGENT/2019/015supported by the Slovenian Research Agency(research core Funding No.P1-0035)by CAS President’s International Fellowship Initiative(PIFI)(Grant No.2024PVA0004)。
文摘In 2021,the Belle collaboration reported the first observation of a new structure in theψ(2S)γfinal state produced in the two-photon fusion process.In the hadronic molecule picture,this new structure can be associatedwith the shallow isoscalar D*D* bound state and as such is an excellent candidate for the spin-2 partner of the X(3872)with the quantum numbers J^(PC)=2^(++)conventionally named X_(2).
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA25050100)the National Natural Science Foundation of China(Grant Nos.11975154,11675108,11655002,and 11775144)+3 种基金the Science Challenge Project(Grant No.TZ2018005)the China Scholarship Council,the China and Germany Postdoctoral Exchange Program from the Office of China Postdoctoral Council and the Helmholtz Centre(Grant No.20191016)the China Postdoctoral Science Foundation(Grant No.2018M641993)funding from the European Union Horizon 2020 Research and Innovation Programme under Grant Agreement No.633053.
文摘Sunlight-like lasers that have a continuous broad frequency spectrum,random phase spectrum,and random polarization are formulated theoretically.With a sunlight-like laser beam consisting of a sequence of temporal speckles,the resonant three-wave coupling that underlies parametric instabilities in laser–plasma interactions can be greatly degraded owing to the limited duration of each speckle and the frequency shift between two adjacent speckles.The wave coupling can be further weakened by the random polarization of such beams.Numerical simulations demonstrate that the intensity threshold of stimulated Raman scattering in homogeneous plasmas can be doubled by using a sunlight-like laser beam with a relative bandwidth of∼1%as compared with a monochromatic laser beam.Consequently,the hot-electron generation harmful to inertial confinement fusion can be effectively controlled by using sunlight-like laser drivers.Such drivers may be realized in the next generation of broadband lasers by combining two or more broadband beams with independent phase spectra or by applying polarization smoothing to a single broadband beam.
基金Project supported by the Social Science Foundation of Beijing(Grant No.19GLC078)the Fundamental Research Funds for the Central Universities,China(Grant No.2019JKF429).
文摘Campus security has aroused many concerns from the whole society.Stampede is one of the most frequent and influential accidents in campus.Studies on pedestrian dynamics especially focusing on students are essential for campus security,which are helpful to improve facility design and emergency evacuation strategy.In this paper,primary and middle school students were recruited to participate in the single-file experiments.The microscopic movement characteristics,including walking speed,headway,gait characteristics(step length,step frequency and swaying amplitude)and their relations were investigated.Age and gender differences in the headway-speed diagram and space requirements were analyzed by statistical tests.The results indicated that the impacts of age and gender were significant.There were three stages for the influence of gender on the headway-speed diagram for both age groups.The impacts on students'space requirements were consistent for different age and gender groups.But the impacts of age and gender on free-flow speed were affected by each other.Due to the connection of walking speed and gait characteristics,the comparisons of gait characteristics between different ages and genders were performed to understand the corresponding differences in speed more deeply.The results showed that differences in step length and swaying amplitude between males and females were significant for both age groups.The effect of gender on step frequency was significant for primary students.But for middle school students,whether gender had significant impact on step frequency was not clear here because of the large P-value.Besides,the influence of age on gait characteristics changed with gender.
基金Supported in part by the DFG and the NSFC through funds provided to the Sino-German CRC 110 ＂Symmetries and the Emergence of Structure in QCD＂, and by the NSFC under Grant No. 11165005
文摘We study prompt hadroproduction of the charged bottomonium-like states Zb± （10610） and Zb±（10650）, and the charged eharmonium-like states Zc± （3900） and Zc± （4020）, at the Tevatron and the LHC, provided that these states are S-wave hadronic molecules. Using two Monte Carlo event generators, Herwig and Pythia, to simulate the production of heavy meson pairs, we derive an order-of-magnitude estimate of the production rates for these four particles. Our estimates yield a cross section at the nb level for the Zb（10610） and Zb（10650）. The results for the Zc（3900） and Zc （4020） are larger by a factor of 2~30. These cross sections are large enough to be observed, and measurements at hadron colliders in the future will supplement the study using electron-positron collisions, and therefore allow to explore the mysterious nature of these exotic states.
文摘Counterfactual definiteness must be used as at least one of the postulates or axioms that are necessary to derive Bell-type inequalities. It is considered by many to be a postulate that not only is commensurate with classical physics (as for example Einstein’s special relativity), but also separates and distinguishes classical physics from quantum mechanics. It is the purpose of this paper to show that Bell’s choice of mathematical functions and independent variables implicitly includes counterfactual definiteness. However, his particular choice of variables reduces the generality of his theory, as well as the physics of all Bell-type theories, so significantly that no meaningful comparison of these theories with actual Einstein-Podolsky-Rosen experiments can be made.
基金Supported by National Natural Science Foundation of China uder Grant Nos.11805059,11805012,11805037Fundamental Research Funds for the Central Universities+6 种基金the Joint Large Scale Scientific Facility Funds of the NSFCChinese Academy of Sciences(CAS)under Grant No.U1832121Shanghai Pujiang Program under Grant No.18PJ1401000Open Research Program of Large Research Infrastructures(2017)CAS,the DFG(SFB/TR 110,“Symmetries and the Emergence of Structure in QCD”)the Chinese Academy of Sciences(CAS) President’s International Fellowship Initiative(PIFI)under Grant No.2018DM0034Volkswagen Stiftung under Grant No.93562
文摘In this paper we propose a dispersive method to describe two-body scattering with unitarity imposed.This approach is applied to elasticππscattering.The amplitudes keep single-channel unitarity and describe the experimental data well,and the low-energy amplitudes are consistent with that of chiral perturbation theory.The pole locations of theσ,f0(980),ρ(770)and f_(2)(1270)and their couplings toππare obtained.A virtual state appearing in the isospin-two S-wave is confirmed.The correlations between the left(and right)hand cut and the poles are discussed.Our results show that the poles are more sensitive to the right hand cut rather than the left hand cut.The proposed method could be used to study other two-body scattering processes.
文摘Machine learning has become a premier tool in physics and other fields of science.It has been shown that the quantum mechanical scattering problem cannot only be solved with such techniques,but it was argued that the underlying neural network develops the Bom series for shallow potentials.However,classical machine learning algorithms fail in the unitary limit of an infinite scattering length.The unitary limit plays an important role in our understanding of bound strongly interacting fermionic systems and can be realized in cold atom experiments.Here,we develop a formalism that explains the unitary limit in terms of what we define as unitary limit surfaces.This not only allows to investigate the unitary limit geometrically in potential space,but also provides a numerically simple approach towards unnaturally large scattering lengths with standard multilayer perceptrons.Its scope is therefore not limited to applications in nuclear and atomic physics,but includes all systems that exhibit an unnaturally large scale.
基金DFG and NSFC through funds provided to the Sino-German CRC 110’Symmetries and the Emergence of Structure in QCD’(NSFC Grant No.11621131001,DFG Grant No.TRR110)Volkswagen Stiftung(Grant no.93562)the CAS President’s International Fellowship Initiative(PIFI)(Grant No.2018DM0034)。
文摘We calculate the energy levels corresponding to the Roper resonance based on a two-flavor chiral effective Lagrangian for pions,nucleons,deltas,and the Roper resonance at the leading one-loop order.We show that the Roper mass can be extracted from these levels for lattice volumes of moderate size.
基金supported in part by the DFG(Projektnummer 196253076—TRR 110)the NSFC(Grant No.11621131001)through the funds provided to the Sino-German CRC 110‘Symmetries and the Emergence of Structure in QCD’+3 种基金by the Alexander von Humboldt Foundation through the Humboldt Research Fellowshipby the Chinese Academy of Sciences(CAS)through a President’s International Fellowship Initiative(PIFI)(Grant No.2018DM0034)by the Volkswagen Stiftung(Grant No.93562)by the EU Horizon 2020 research and innovation programme,STRONG-2020 project under grant agreement No.824093。
文摘based on our analysis of the contributions from the connected and disconnected contraction diagrams to the pion-kaon scattering amplitude,we provide the first determination of the only free low-energy constant at O(p^(4)),known as L_(0)^(r),in SU(4|1)Partially-Quenched Chiral Perturbation theory using the data from the Extended Twisted Mass collaboration,L_(0)^(r)(μ=M_(ρ))=0.77(20)(25)(7)(7)(2)·10^(-3).The theory uncertainties originate from the unphysical scattering length,the physical low-energy constants,the higher-order chiral corrections,the(lattice)meson masses and the pion decay constant,respectively.
基金supported in part by the National Natural Science Foundation of China(NSFC)the Deutsche Forschungsgemeinschaft(DFG)through the funds provided to the Sino-German Collaborative Research Center TRR110‘Symmetries and the Emergence of Structure in QCD’(NSFC Grant No.12070131001,DFG Project-ID 196253076)+3 种基金the Chinese Academy of Sciences(CAS)under Grant No.XDB34030000the NSFC under Grants Nos.12125507,11835015,and 12047503CAS through the President’s International Fellowship Initiative(PIFI)(Grant No.2018DM0034)the Volkswagen Stiftung(Grant No.93562)
文摘The internal structure of the charm-strange mesons D_(s0)^(*)(2317)and D_(s1)(2460)are the subject of intensive studies.Their widths are small because they decay dominantly through isospinbreaking hadronic channels D_(s0)^(*)(2317)^(+)→D_(s)^(+)π^(0) and D _(s1)(2460)^(+)→D_(s)^(*+)π^(0).The D_(s1)(2460)can also decay into the hadronic final states D_(s)^(+)ππ,conserving isospin.In that case there is,however,a strong suppression from phase space.We study the transition D_(s1)(2460)^(+)→D_(s)^(+)π^(+)π^(-)in the scenario that the D_(s1)(2460)is a D^(*)K hadronic molecule.The ππ final state interaction is taken into account through dispersion relations.We find that the ratio of the partial widths of the Γ(D_(s1)(2460)^(+)→D_(s)^(+)π^(+)π^(-)) / Γ(D_(s1)(2460)^(+)→D_(s)^(*+)π^(0))obtained in the molecular picture is consistent with the existing experimental measurement.More interestingly,we demonstrate that theπ+π−invariant mass distribution shows a double bump structure,which can be used to disentangle the hadronic molecular picture from the compact state picture for the D_(s1)(2460)^(+).Predictions on the B_(s1)^(0)→B_(s)^(0)π^(+)π^(-)are also made.
基金This work was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA25050100)the National Natural Science Foundation of China(Grant Nos.11991074,11975154,12005287,and 12135009)+2 种基金the Science Challenge Project(Grant No.TZ2018005)X.F.Li was supported by the China and Germany Postdoctoral Exchange Program from the Office of the China Postdoctoral Council and the Helmholtz Centre(Grant No.20191016)and the China Postdoctoral Science Foundation(Grant No.2018M641993)Y.Zhao was also supported by Guangdong Basic and Applied Basic Research Foundation(Grant No.2023A1515011695).Simulations were carried out on the JURECA and JUWELS supercomputers at the Jülich Supercomputing Centre,which are granted from the Projects JZAM04 and LAPIPE.
文摘Broadband lasers have been proposed as future drivers of inertial confined fusion(ICF)to enhance the laser-target coupling efficiency via the mitigation of various parametric instabilities.The physical mechanisms involved have been explored recently,but are not yet fully understood.Here,stimulated Raman scattering(SRS)as one of the key parametric instabilities is investigated theoretically and numerically for a broadband laser propagating in homogeneous plasma in multidimensional geometry.The linear SRS growth rate is derived as a function of scattering angles for two monochromatic laser beams with a fixed frequency differenceδω.Ifδω/ω_(0)∼1%,withω0 the laser frequency,these two laser beams may be decoupled in stimulating backward SRS while remaining coupled for sideward SRS at the laser intensities typical for ICF.Consequently,side-scattering may dominate over backward SRS for two-color laser light.This finding of SRS transition from backward to sideward SRS is then generalized for a broadband laser with a few-percent bandwidth.Particle-in-cell simulations demonstrate that with increasing laser bandwidth,the sideward SRS gradually becomes dominant over the backward SRS.Since sideward SRS is very efficient in producing harmful hot electrons,attention needs to be paid on this effect if ultra-broadband lasers are considered as next-generation ICF drivers.
基金Supported in part by DFG and NSFC through funds provided to the Sino-German CRC 110“Symmetries and the Emergence of Structure in QCD”National Natural Science Foundation of under Grant No.11621131001,DFG under Grant No.TRR110the Georgian Shota Rustaveli National Science Foundation(Grant FR/417/6-100/14)the Chinese Academy of Sciences President’s International Fellowship Initiative(PIFI)under Grant No.2017VMA0025
文摘Quantum electrodynamics is often considered to be a trivial theory.This is based on a number of evidences,both numerical and analytical.One of the strong indications for triviality of QED is the existence of the Landau pole for the running coupling.We show that by treating QED as the leading order approximation of an effective field theory and including the next-to-leading order corrections,the Landau pole is removed.We also analyze the cutoff dependence of the bare coupling at two-loop order and conclude that the conjecture,that for reasons of self-consistency,QED needs to be trivial is a mere artefact of the leading order approximation to the corresponding effective field theory.
基金Supported by DFG and National Natural Science Foundation of China Through Funds Provided to the Sino-German CRC 110"Symmetriesthe Emergence of Structure in QCD"(National Natural Science Foundation of China under Grant No.11261130311)+1 种基金the Thousand Talents Plan for Young Professionalsand the Chinese Academy of Sciences President’s International Fellowship Initiative under Grant No.2015VMA076
文摘We discuss the X(5568)particle recently announced by the D0 Collaboration.Several types of models were proposed to explain this structure in the literature.As pointed out by Burns and Swanson(ar Xiv:1603.04366),none of them provides a satisfactory description of the observation.We provide additional arguments using general properties of QCD,and conclude that the observation of the X(5568),if confirmed,poses serious challenges to our understanding of nonperturbative QCD.
基金Supported in part by BMBF under Grant No.05P2015–NUSTAR R&D)DFG and NSFC through Funds Provided to the SinoGerman CRC 110 “Symmetries and the Emergence of Structure in QCD”+2 种基金National Natural Science Foundation of China under Grant No.11621131001,DFG Grant No.TRR110the Georgian Shota Rustaveli National Science Foundation(grant FR/417/6-100/14)the CAS President’s International Fellowship Initiative(PIFI)under Grant No.2017VMA0025
文摘The Wilsonian renormalization group approach to the Lippmann-Schwinger equation with a multitude of cutoff parameters is introduced.A system of integro-differential equations for the cutoff-dependent potential is obtained.As an illustration,a perturbative solution of these equations with two cutoff parameters for a simple case of an S-wave low-energy potential in the form of a Taylor series in momenta is obtained.The relevance of the obtained results for the effective field theory approach to nucleon-nucleon scattering is discussed.
基金Supported in part by the National Natural Science Foundation of China(NSFC)(11975041,11961141004)Xiang-Xiang Sun is supported in part by NSFC(12205308)the Deutsche Forschungsgemeinschaft(DFG)and NSFC through the funds provided to the Sino-German Collaborative Research Center TRR110"Symmetries and the Emergence of Structure in QCD"(NSFC Grant No.12070131001,DFG Project-ID 196253076)。
文摘Magicity,or shell closure,plays an important role in our understanding of complex nuclear phenomena.In this work,we employ one of the state-of-the-art density functional theories,the deformed relativistic Hartree-Bogoliubov theory in continuum(DRHBc)with the density functional PC-PK1,to investigate the evolution of the N=20,28,50 shell closures in the 20≤Z≤30 region.We show how these three conventional shell closures evolve from the proton drip line to the neutron drip line by studying the charge radii,two-neutron separation energies,two-neutron gaps,quadrupole deformations,and single-particle levels.In particular,we find that in the 21≤Z≤27 region,the N=50 shell closure disappears or becomes quenched,mainly due to the deformation effects.Similarly,both experimental data and theoretical predictions indicate that the N=28 shell closure disappears in the Mn isotopic chain,mainly due to the deformation effects.The DRHBc theory predicts the existence of the N=20 shell closure in the Ca,Sc,and Ti isotopic chains,but the existing data for the Ti isotopes suggest the contrary,and therefore further research is needed.
