Measuring cross sections of nuclear reactions,such as the so-called“Holy Grail”reaction,^(12)C(σ,γ)^(16)O,is essential for understanding stellar nucleosynthesis but presents significant challenges due to extremely...Measuring cross sections of nuclear reactions,such as the so-called“Holy Grail”reaction,^(12)C(σ,γ)^(16)O,is essential for understanding stellar nucleosynthesis but presents significant challenges due to extremely low cross sections.Key challenges include significant energy loss as ions penetrate the target material,limiting measurements to thin target layers.To overcome these obstacles,we propose a novel method,the in-target energy loss compensating(eLOC)method,specifically designed for gas targets,which utilizes a gas-filled magnetic field and accelerating electric fields to compensate for ion energy loss in the target.Simulations show that this approach significantly enhances the effective target thickness by over 140 times in the case of the“Holy Grail”reaction with an inverse-kinematics setup.This eLOC method may provide a powerful new tool for obtaining critical data in nuclear astrophysics,thereby advancing our understanding of stellar nucleosynthesis and the origins of elements in the universe,as well as benefiting other related fields such as isotope production.展开更多
Theoretical calculations serve as an effective method for determining plasma temperatures within planetary atmospheres.To simulate plasma temperature,a comprehensive implementation of the energy equation is used,which...Theoretical calculations serve as an effective method for determining plasma temperatures within planetary atmospheres.To simulate plasma temperature,a comprehensive implementation of the energy equation is used,which is governed by five terms:conductivity,heating,cooling,adiabatic expansion,and advection.The derivations mentioned are strongly dependent on the collision cross section between electrons and other particles(e.g.,neutrals,ions).It is notable that the momentum transfer cross sections between electrons and neutrals have been updated in recent decades.However,the widely used momentum average collision cross sections between electrons and neutrals,derived from the momentum transfer cross sections,are collected in studies dating back nearly half a century.Therefore,it becomes imperative to revise the momentum average collision cross sections relevant to astrophysical contexts,based on the latest studies.In this study,we summarize the momentum average collision cross sections of 13 species common in planetary atmospheres:H,H_(2),He,O,CH_(4),H_(2)O,CO,N_(2),O_(2),Ar,CO_(2),N_(2)O,and NO_(2).All results are derived from the latest studies concerning the electron-neutral collision cross section and are compared with previous studies.Furthermore,we present a comparison of the derived total electron-neutral collision frequency at Mars between this study and previous studies.Prominent differences in the total electron-neutral collision frequency between this and prior studies support the significance of updating the momentum average collision cross section between electrons and neutrals in studying the planetary atmospheres.展开更多
This letter reports a gravitational redshift measurement experiment using a satellite-based compact passive hydrogen maser(PHM)in a lunar distant retrograde orbit(DRO).In March 2024,the Chinese Academy of Sciences lau...This letter reports a gravitational redshift measurement experiment using a satellite-based compact passive hydrogen maser(PHM)in a lunar distant retrograde orbit(DRO).In March 2024,the Chinese Academy of Sciences launched the DRO-A/B twin satellites,which entered a DRO in July 2024.This orbit has a geocentric distance of approximately 300,000–450,000 kilometers and a 2:1 resonance ratio.Employing microwave dual one-way ranging(DOWR),satellite-ground time-frequency comparisons were successfully achieved in April 2025 using the PHM aboard the DRO-A satellite.This study validated the in-orbit performance of the compact PHM and supported tests of the Einstein Equivalence Principle.The gravitational redshift measurement result is(8.74±4.17)×10^(−3).As the world’s first fundamental physics experiment to deploy PHMs in a lunar DRO,this study provides significant new engineering approaches for testing gravitational theories in cislunar space.展开更多
The accumulation and circulation of carbon and hydrogen contribute to the chemical evolution of ice giant planets.Species separation and diamond precipitation have been reported in carbon-hydrogen systems and have bee...The accumulation and circulation of carbon and hydrogen contribute to the chemical evolution of ice giant planets.Species separation and diamond precipitation have been reported in carbon-hydrogen systems and have been verified by static and shock compression experiments.Nevertheless,the dynamic formation processes underlying these phenomena remain insufficiently understood.In combination with a deep learning model,we demonstrate that diamonds form through a three-step process involving dissociation,species separation,and nucleation processes.Under shock conditions of 125 GPa and 4590 K,hydrocarbons decompose to give hydrogen and low-molecular-weight alkanes(CH_(4) and C_(2)H_(6)),which escape from the carbon chains,resulting in C/H species separation.The remaining carbon atoms without C-H bonds accumulate and nucleate to form diamond crystals.The process of diamond growth is associated with a critical nucleus size at which the dynamic energy barrier plays a key role.These dynamic processes of diamond formation provide insight into the establishment of a model for the evolution of ice giant planets.展开更多
In this study,we present a comprehensive analysis of a modified Frolov black hole(BH)model that incorporates two types of topological defects,a global monopole(GM)and a cloud of strings(CS).This composite BH solution ...In this study,we present a comprehensive analysis of a modified Frolov black hole(BH)model that incorporates two types of topological defects,a global monopole(GM)and a cloud of strings(CS).This composite BH solution is examined from multiple theoretical perspectives to explore the impact of these modifications on the BH's geometric,thermodynamic and dynamical properties.We begin by studying the geometrical optics of the spacetime,focusing on the motion of null geodesics.Key features,such as the effective potential,photon sphere,the force acting on photons and the stability of circular photon orbits,are analyzed in detail.Our results show that the presence of GM and CS significantly affects the spacetime geometry and photon dynamics.In addition,the thermodynamic behavior of the modified BH is also investigated.We derive essential quantities such as the Hawking temperature and entropy,demonstrating how the inclusion of GM and CS leads to deviations from the standard thermodynamic relations observed in classical BH solutions.These deviations may offer valuable insights into quantum gravity and the role of topological defects in BH physics.Furthermore,we examine the BH shadow as an observational signature of the underlying geometry.Our analysis shows that the Frolov parameter tends to reduce the apparent size of the shadow,while the presence of topological defects,particularly GM and CS,enlarges it.In addition,we investigate the perturbative dynamics of the BH by studying both scalar(spin-0),fermionic(spin-1/2)and electromagnetic(spin-1)fields through the massless Klein-Gordon and Maxwell equations,respectively.Using the Wentzel-Kramers-Brillouin approximation,we compute the quasinormal modes(QNMs)for scalar and electromagnetic field perturbations.The results confirm the stability of the BH under small perturbations and show that the QNM frequencies and damping rates are strongly influenced by the Frolov parameter,electric charge,GM and CS.展开更多
基金supported by the the National Key R&D Program of China (Grant Nos.2023YFA1606900 and 2022YFA1602301)the National Natural Science Foundation of China (Grant Nos.12235003,12435010,and 12147101)+3 种基金the Guangdong Major Project of Basic and Applied Basic Research (Grant No.2020B0301030008)the STCSM (Grant No.23590780100)the Natural Science Foundation of Shanghai (Grant No.23JC1400200)the China Postdoctoral Science Foundation (Grant No.2024M760483)。
文摘Measuring cross sections of nuclear reactions,such as the so-called“Holy Grail”reaction,^(12)C(σ,γ)^(16)O,is essential for understanding stellar nucleosynthesis but presents significant challenges due to extremely low cross sections.Key challenges include significant energy loss as ions penetrate the target material,limiting measurements to thin target layers.To overcome these obstacles,we propose a novel method,the in-target energy loss compensating(eLOC)method,specifically designed for gas targets,which utilizes a gas-filled magnetic field and accelerating electric fields to compensate for ion energy loss in the target.Simulations show that this approach significantly enhances the effective target thickness by over 140 times in the case of the“Holy Grail”reaction with an inverse-kinematics setup.This eLOC method may provide a powerful new tool for obtaining critical data in nuclear astrophysics,thereby advancing our understanding of stellar nucleosynthesis and the origins of elements in the universe,as well as benefiting other related fields such as isotope production.
基金the National Natural Science Foundation of China through Grants 42261160643,42441806,42241114,and 42304166supported by the open project funded by the Key Laboratory of Geospace Environment,Chinese Academy of Sciences,University of Science and Technology of China.
文摘Theoretical calculations serve as an effective method for determining plasma temperatures within planetary atmospheres.To simulate plasma temperature,a comprehensive implementation of the energy equation is used,which is governed by five terms:conductivity,heating,cooling,adiabatic expansion,and advection.The derivations mentioned are strongly dependent on the collision cross section between electrons and other particles(e.g.,neutrals,ions).It is notable that the momentum transfer cross sections between electrons and neutrals have been updated in recent decades.However,the widely used momentum average collision cross sections between electrons and neutrals,derived from the momentum transfer cross sections,are collected in studies dating back nearly half a century.Therefore,it becomes imperative to revise the momentum average collision cross sections relevant to astrophysical contexts,based on the latest studies.In this study,we summarize the momentum average collision cross sections of 13 species common in planetary atmospheres:H,H_(2),He,O,CH_(4),H_(2)O,CO,N_(2),O_(2),Ar,CO_(2),N_(2)O,and NO_(2).All results are derived from the latest studies concerning the electron-neutral collision cross section and are compared with previous studies.Furthermore,we present a comparison of the derived total electron-neutral collision frequency at Mars between this study and previous studies.Prominent differences in the total electron-neutral collision frequency between this and prior studies support the significance of updating the momentum average collision cross section between electrons and neutrals in studying the planetary atmospheres.
文摘This letter reports a gravitational redshift measurement experiment using a satellite-based compact passive hydrogen maser(PHM)in a lunar distant retrograde orbit(DRO).In March 2024,the Chinese Academy of Sciences launched the DRO-A/B twin satellites,which entered a DRO in July 2024.This orbit has a geocentric distance of approximately 300,000–450,000 kilometers and a 2:1 resonance ratio.Employing microwave dual one-way ranging(DOWR),satellite-ground time-frequency comparisons were successfully achieved in April 2025 using the PHM aboard the DRO-A satellite.This study validated the in-orbit performance of the compact PHM and supported tests of the Einstein Equivalence Principle.The gravitational redshift measurement result is(8.74±4.17)×10^(−3).As the world’s first fundamental physics experiment to deploy PHMs in a lunar DRO,this study provides significant new engineering approaches for testing gravitational theories in cislunar space.
基金supported by the National Natural Science Foundation of China(Grant Nos.12534013,12047561,and 12104507)the Science and Technology Innovation Program of Hunan Province(Grant Nos.2025ZYJ001 and 2021RC4026)the National University of Defense Technology Research Fund Project.
文摘The accumulation and circulation of carbon and hydrogen contribute to the chemical evolution of ice giant planets.Species separation and diamond precipitation have been reported in carbon-hydrogen systems and have been verified by static and shock compression experiments.Nevertheless,the dynamic formation processes underlying these phenomena remain insufficiently understood.In combination with a deep learning model,we demonstrate that diamonds form through a three-step process involving dissociation,species separation,and nucleation processes.Under shock conditions of 125 GPa and 4590 K,hydrocarbons decompose to give hydrogen and low-molecular-weight alkanes(CH_(4) and C_(2)H_(6)),which escape from the carbon chains,resulting in C/H species separation.The remaining carbon atoms without C-H bonds accumulate and nucleate to form diamond crystals.The process of diamond growth is associated with a critical nucleus size at which the dynamic energy barrier plays a key role.These dynamic processes of diamond formation provide insight into the establishment of a model for the evolution of ice giant planets.
基金financial support from EMU, TÜBİTAK, ANKOS and SCOAP3
文摘In this study,we present a comprehensive analysis of a modified Frolov black hole(BH)model that incorporates two types of topological defects,a global monopole(GM)and a cloud of strings(CS).This composite BH solution is examined from multiple theoretical perspectives to explore the impact of these modifications on the BH's geometric,thermodynamic and dynamical properties.We begin by studying the geometrical optics of the spacetime,focusing on the motion of null geodesics.Key features,such as the effective potential,photon sphere,the force acting on photons and the stability of circular photon orbits,are analyzed in detail.Our results show that the presence of GM and CS significantly affects the spacetime geometry and photon dynamics.In addition,the thermodynamic behavior of the modified BH is also investigated.We derive essential quantities such as the Hawking temperature and entropy,demonstrating how the inclusion of GM and CS leads to deviations from the standard thermodynamic relations observed in classical BH solutions.These deviations may offer valuable insights into quantum gravity and the role of topological defects in BH physics.Furthermore,we examine the BH shadow as an observational signature of the underlying geometry.Our analysis shows that the Frolov parameter tends to reduce the apparent size of the shadow,while the presence of topological defects,particularly GM and CS,enlarges it.In addition,we investigate the perturbative dynamics of the BH by studying both scalar(spin-0),fermionic(spin-1/2)and electromagnetic(spin-1)fields through the massless Klein-Gordon and Maxwell equations,respectively.Using the Wentzel-Kramers-Brillouin approximation,we compute the quasinormal modes(QNMs)for scalar and electromagnetic field perturbations.The results confirm the stability of the BH under small perturbations and show that the QNM frequencies and damping rates are strongly influenced by the Frolov parameter,electric charge,GM and CS.
