Prior empirical studies find positive and negative momentum effect across the global nations, but few focus on explaining the mixed results. In order to address this issue, we apply the quantile regression approach to...Prior empirical studies find positive and negative momentum effect across the global nations, but few focus on explaining the mixed results. In order to address this issue, we apply the quantile regression approach to analyze the momentum effect in the context of Chinese stock market in this paper. The evidence suggests that the momentum effect in Chinese stock is not stable across firms with different levels of performance. We find that negative momentum effect in the short and medium horizon （3 months and 9 months） increases with the quantile of stock returns. And the positive momentum effect is observed in the long horizon （12 months）, which also intensifies for the high performing stocks. According to our study, momentum effect needs to be examined on the basis of stock returns. OLS estimation, which gives an exclusive and biased result, provides misguiding intuitions for momentum effect across the global nations. Based on the empirical results of quantile regression, effective risk control strategies can also be inspired by adjusting the proportion of assets with past performances.展开更多
New theoretical calculations are performed to investigate the Coulomb proximity and angular momentum effects on multifragmentation picture for84Kr+112,124 Sn collisions at an incident beam energy of 35 Me V/nucleon.Ch...New theoretical calculations are performed to investigate the Coulomb proximity and angular momentum effects on multifragmentation picture for84Kr+112,124 Sn collisions at an incident beam energy of 35 Me V/nucleon.Charge and isotopic distributions and the mean neutron-to-proton ratios of the fragments are reproduced within the microcanonical Markov chain calculations on the basis of Statistical Multifragmentation Model. It is shown that the Coulomb interactions and angular momentum effects are very important to reproduce isotopic composition of nuclear fragments in peripheral heavy-ion collisions at Fermi energies. Our results imply that it is possible to investigate in laboratories the modification of structure parameters of fragments, such as the symmetry energy coefficient, at subnuclear densities in dense environment of other species.展开更多
The relativistic and distorted wave effects are investigated for the electron momentum distributions of Xe 4d electrons.The theoretical results show good agreements with the experimental data measured previously with ...The relativistic and distorted wave effects are investigated for the electron momentum distributions of Xe 4d electrons.The theoretical results show good agreements with the experimental data measured previously with electron momentum spectroscopy. The distorted wave effect and the relativistic effect are found to play important roles in the low and high momentum regions, respectively.展开更多
This paper proposes a modified strong field approximation model for evaluating nondipole effects on the ionization of an atom in an intense laser field. The photoelectron longitudinal momentum distributions （PLMD） o...This paper proposes a modified strong field approximation model for evaluating nondipole effects on the ionization of an atom in an intense laser field. The photoelectron longitudinal momentum distributions （PLMD） of a hydrogen-like atom exposed to a mid-infrared laser field is calculated. The theoretical results indicate an obvious asymmetry in the PLMD, and an offset of the PLMD peak appears in the opposite direction of the beam propagation due to nondipole effects. The peak offsets of the PLMD increased with the laser intensity, imposed by the initial state of the hydrogen-like atom.展开更多
Based on the generalized uncertainty principle with maximum momentum arid minimal length, we discuss the equation of state of ideal ultra-relativistic Fermi gases at zero temperature. Maximum momentum avoids the probl...Based on the generalized uncertainty principle with maximum momentum arid minimal length, we discuss the equation of state of ideal ultra-relativistic Fermi gases at zero temperature. Maximum momentum avoids the problem that the Fermi degenerate pressure blows up since the increase of the Fermi energy is not limited. Applying this equation of state to the Tolman-Oppenheimer Volkoff （TOV） equation, the quantum gravitational effects on the cores of compact stars are discussed. In the center of compact stars, we obtain the singularity-free solution of the metric component, gtt ～-（1 ＋ 0.2185×r^2）. By numerically solving the TOV equation, we find that quantum gravity plays an important role in the region r～10^4α0（△x）min. Current observed masses of neutron stars indicate that the dimensionless parameter α0 cannot exceed 10^19.展开更多
The outer valence electron momentum distributions of benzene are reinvestigated with theoretical calculations involving the vibrational effects.The results are compared with recent experimental measurements[Phys.Rev.A...The outer valence electron momentum distributions of benzene are reinvestigated with theoretical calculations involving the vibrational effects.The results are compared with recent experimental measurements[Phys.Rev.A 98042705(2018)].The significant discrepancies between theories and experiments in previous works have now been interpreted quantitatively,indicating that the vibrational motion in benzene molecule has noticeable influence on its electron momentum distributions.展开更多
The electronic structure of five conformers of 2-chloroethanol was studied by ab initio calculations at B3LYP and MP2 levels of theory with aug-cc-pVTZ basis set. The existing hydrogen bond and hyperconjugation effect...The electronic structure of five conformers of 2-chloroethanol was studied by ab initio calculations at B3LYP and MP2 levels of theory with aug-cc-pVTZ basis set. The existing hydrogen bond and hyperconjugation effects on the stability of 2-chloroethanol conformers were discussed on the base of natural bond orbital analyses. The result exhibits that hyperconjugation is the main factor to determine the stability of conformers. Such effects on the electron wavefunctions of the highest-occupied molecular orbital （HOMO） of different conformers are demonstrated with electron momentum spectroscopy, exhibiting the obviously different symmetries of the HOMO wavefunctions in momentum space.展开更多
Although equivalent in the infinite-momentum limit,large-momentum effective theory(LaMET)and short-distance operator product expansion(SDE)are 2 very different approaches to obtain parton distribution functions(PDFs)f...Although equivalent in the infinite-momentum limit,large-momentum effective theory(LaMET)and short-distance operator product expansion(SDE)are 2 very different approaches to obtain parton distribution functions(PDFs)from coordinate-space correlation functions computed in a large-momentum proton through lattice quantum chromodynamics(QCD).LaMET implements a momentum-space expansion inΛ_(QCD)[/x(1-x)P^(z)]to directly calculate PDFs f(x)in a middle region of Bjorken x∈[x_(min)~Λ_(QCD)/xP^(z)x_(max)~1-x_(min)].SDE applies perturbative QCD at small Euclidean distances z to extract a range[0,λ_(max)]of leading-twist correlations,h(λ=zP^(z)),corresponding to the Fourier transformation of PDFs.An incomplete leading-twist correlation from SDE cannot be readily converted to a momentum-space distribution,and solving its constraints on the PDFs(or the so-called"inverse problem")involves phenomenological modeling of the missing information beyondλ_(max)and has no systematic control of errors.I argue that the best use of short-distance correlations is to constrain the PDFs in the LaMET-complementary regions:x∈[0,x_(min)]and[x_(max),1]through expected end-point asymptotics,and use the results of the pion valence quark distribution from the ANL/BNL collaboration to demonstrate how this can be done.展开更多
In this review,we will focus on recent progress on the investigations of nondipole effects in few-electron atoms and molecules interacting with light fields.We first briefly survey several popular theoretical methods ...In this review,we will focus on recent progress on the investigations of nondipole effects in few-electron atoms and molecules interacting with light fields.We first briefly survey several popular theoretical methods and relevant concepts in strong field and attosecond physics beyond the dipole approximation.Physical phenomena stemming from the breakdown of the dipole approximation are then discussed in various topics,including the radiation pressure and photon-momentum transfer,the atomic stabilization,the dynamic interference,and the high-order harmonic generation.Whenever available,the corresponding experimental observations of these nondipole effects are also introduced respectively in each topics.展开更多
For the traditional photonic crystal fibers with circular air holes, rectangular air holes are added to the fiber cladding. The periodic arrangement of the inner rectangular air holes allows the fiber structure to bet...For the traditional photonic crystal fibers with circular air holes, rectangular air holes are added to the fiber cladding. The periodic arrangement of the inner rectangular air holes allows the fiber structure to better match the annular mode field distribution of the vortex beam. The fiber structure was analyzed and calculated by COMSOL Multiphysics 5.4 finite element software, and the characteristics of fiber were analyzed, such as the dispersion, confinement loss, effective mode area and nonlinear coefficient. The results reveal that the photonic crystal fiber structure capable of carrying 50 orbital angular momentum (OAM) modes at the wavelength of 1.15 to 2.0 μm (850 nm). The effective refractive index difference Δneff between vector modes can reach 1 × 10-3, and larger difference can effectively separate the vector modes and improve the transmission performance of OAM modes. Moreover, the fiber has good performance, such as flat dispersion distribution of the low-order modes, low confinement loss below 10-9 dB·m-1, large effective mode field area and small nonlinear coefficient in the 850 nm wavelength range. Therefore, this fiber structure can be applied to the high-capacity communication system of fiber multiplexing OAM. In addition, the good characteristics of this fiber structure are of great significance for the transmission of vortex beam in fiber.展开更多
A simplified one-dimensional barotropic vorticity equation is used to study the influences of the vorticity and the momentum source on the large scale wave. Both vorticity source and momentum source can cause the form...A simplified one-dimensional barotropic vorticity equation is used to study the influences of the vorticity and the momentum source on the large scale wave. Both vorticity source and momentum source can cause the formation of the large scale wave, but the former can produce large scale wave only under the condition that there is apparent basic flow acting on it, while the latter can produce the large scale wave even when tends to be zero. Furthermore, the amplitude of steady wave caused by the former is proportional to , while the amplitude caused by the latter has no relation to , instead it depends only on the magnitude of the perturbation of momentum.展开更多
An isospin-dependent quantum molecular dynamical model （IQMD） is developed, with the isospin degree of freedom in the momentum-dependent interaction（MDI） included in IQMD, to obtain an isospin- and momentum-depend...An isospin-dependent quantum molecular dynamical model （IQMD） is developed, with the isospin degree of freedom in the momentum-dependent interaction（MDI） included in IQMD, to obtain an isospin- and momentum-dependent interaction （IMDI） in IQMD. We investigate the effect of IMDI on the isospin fractionation ratio and its dynamical mechanism in the intermediate energy heavy ion collisions. It is found that the IMDI induces the significant reductions in the isospin fractionation ratio for all of beam energies, impact parameters, neutron-proton ratios and mass number of colliding systems. However, the strong dependence of isospin fractionation ratio on the symmetrical potential is preserved, with the isospin degree of freedom included in the MDI, i.e. the isospin fractionation ratio is still a good probe for extracting the information about the equation of state of isospin asymmetrical nuclear matter.展开更多
The binding energy spectra and the momentum distributions of the outer valence orbitals of W（CO）6 have been studied by using electron momentum spectroscopy as well as non-relativistic, scalar relativistic and spin-o...The binding energy spectra and the momentum distributions of the outer valence orbitals of W（CO）6 have been studied by using electron momentum spectroscopy as well as non-relativistic, scalar relativistic and spin-orbital relativistic DFT-B3LYP calculations. The experimental momentum profiles of the outer valence orbitals obtained with the impact energies of 1200 eV and 2400 eV were compared with various theoretical calculation results. The relativistic calculations could provide better descriptions for the experimental momentum distributions than the non-relativistic ones. Moreover, a new ordering of orbitals 10tlu, 3t2g, and 7eg, i.e., 10t_lu 〈 3t_2g 〈7e_g 〈10a_lg, is established in this work.展开更多
The first electronic structural study of the complete valence shell binding energy spectra of the antimicrobial agent diacetyl, encompassing both the outer and inner valence regions, is reported. The binding energy sp...The first electronic structural study of the complete valence shell binding energy spectra of the antimicrobial agent diacetyl, encompassing both the outer and inner valence regions, is reported. The binding energy spectra as well as the individual orbital momentum profiles have been measured by using a high resolution （e, 2e） electron momentum spectrometer （EMS） at an impact energy of 1200eV plus the binding energy, and using symmetric noncoplanar kinematics. The experimental orbital electron momentum profiles are compared with self-consistent field （SCF） theoretical profiles calculated using the Hartree-Fock approximation and Density Functional theory predictions in the target Kohn-Sham approximation which includes some treatment of correlation via the exchange and correlation potentials with a range of basis sets. The pole strengths of the main ionization peaks from the inner valence orbitals are estimated.展开更多
In recent years, digital investment portfolios have become a significant area of interest in the field of machine learning. To tackle the issue of neglecting the momentum effect in risk asset prices within the follow-...In recent years, digital investment portfolios have become a significant area of interest in the field of machine learning. To tackle the issue of neglecting the momentum effect in risk asset prices within the follow-the-winner strategy and to evaluate the significance of this effect, a novel measure of risk asset price momentum trend is introduced for online investment portfolio research. Firstly, a novel approach is introduced to quantify the momentum trend effect, which is determined by the product of the slope of the linear regression model and the absolute value of the linear correlation coefficient. Secondly, a new investment portfolio optimization problem is established based on the prediction of future returns. Thirdly, the Lagrange multiplier method is used to obtain the analytical solution of the optimization model, and the soft projection optimization algorithm is used to map the analytical solution to obtain the investment portfolio of the model. Finally, experiments are conducted on five benchmark datasets and compared with popular investment portfolio algorithms. The empirical findings indicate that the algorithm we are introduced is capable of generating higher investment returns, thereby establishing its efficacy for the management of the online investment portfolios.展开更多
The concept of the effective mass in crystals shows that the electron mass is affected by the crystal field and was experimentally verified. A useful expression for effective mass was obtained. Unfortunately this expr...The concept of the effective mass in crystals shows that the electron mass is affected by the crystal field and was experimentally verified. A useful expression for effective mass was obtained. Unfortunately this expression showed that the effective mass vanishes in the ab-sence of the external field. This is in conflict with observations which show that it reduces to the ordinary mass. To cure this defect a new model is developed assuming the existence of vacuum force as verified experimentally as shown by Casimir effect. Using Newton’s second law and the quantum expression of momentum, useful expressions were found. The same expression was found using generalized special relativity. Strikingly the three models reduced to the conventional one in the absence of vacuum, they also reduced to the ordinary electron mass in the absence of all forces.展开更多
By analyzing the Einstein-box thought experiment with the principle of relativity, it is shown that Abraham’s light momentum and energy in a medium cannot constitute a Lorentz four-vector, and they consequentially br...By analyzing the Einstein-box thought experiment with the principle of relativity, it is shown that Abraham’s light momentum and energy in a medium cannot constitute a Lorentz four-vector, and they consequentially break global momentum and energy conservation laws. In contrast, Minkowski’s momentum and energy always constitute a Lorentz four-vector no matter whether in a medium or in vacuum, and the Minkowski’s momentum is the unique correct light momentum. A momentum-associated photon mass in a medium is exposed, which explains why only the Abraham’s momentum is derived in the traditional “center-of-mass-energy” approach. The EM boundary-condition matching approach, combined with Einstein light-quantum hypothesis, is proposed to analyze this thought experiment, and it is found for the first time that only from Maxwell equations without resort to the relativity, the correctness of light momentum definitions cannot be identified. Optical pulling effect is studied as well.展开更多
基金Supported in part by National Natural Science Foundation of China(No.11271368)Beijing Philosophy and Social Science Foundation Grant(No.12JGB051)+3 种基金Project of Ministry of Education supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20130004110007)The Key Program of National Philosophy and Social Science Foundation Grant(No.13AZD064)Fundamental Research Funds for the Central Universities and the Research Funds of Renmin University of China(No.10XNK025)China Statistical Research Project(No.2011LZ031)
文摘Prior empirical studies find positive and negative momentum effect across the global nations, but few focus on explaining the mixed results. In order to address this issue, we apply the quantile regression approach to analyze the momentum effect in the context of Chinese stock market in this paper. The evidence suggests that the momentum effect in Chinese stock is not stable across firms with different levels of performance. We find that negative momentum effect in the short and medium horizon （3 months and 9 months） increases with the quantile of stock returns. And the positive momentum effect is observed in the long horizon （12 months）, which also intensifies for the high performing stocks. According to our study, momentum effect needs to be examined on the basis of stock returns. OLS estimation, which gives an exclusive and biased result, provides misguiding intuitions for momentum effect across the global nations. Based on the empirical results of quantile regression, effective risk control strategies can also be inspired by adjusting the proportion of assets with past performances.
基金Supported by Turkish Scientific and Technical Research Council(No.113F058)Scientific Research Coordination of Selcuk University(BAP)(No.SU-2014/14701490)Helmholtz International Center for FAIR(LOEWE program)
文摘New theoretical calculations are performed to investigate the Coulomb proximity and angular momentum effects on multifragmentation picture for84Kr+112,124 Sn collisions at an incident beam energy of 35 Me V/nucleon.Charge and isotopic distributions and the mean neutron-to-proton ratios of the fragments are reproduced within the microcanonical Markov chain calculations on the basis of Statistical Multifragmentation Model. It is shown that the Coulomb interactions and angular momentum effects are very important to reproduce isotopic composition of nuclear fragments in peripheral heavy-ion collisions at Fermi energies. Our results imply that it is possible to investigate in laboratories the modification of structure parameters of fragments, such as the symmetry energy coefficient, at subnuclear densities in dense environment of other species.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11327404 and U1432118)the Natural Science Research Programme of Education Department of Anhui Province,China(Grant Nos.KJ2013A260 and KJ2016A749)
文摘The relativistic and distorted wave effects are investigated for the electron momentum distributions of Xe 4d electrons.The theoretical results show good agreements with the experimental data measured previously with electron momentum spectroscopy. The distorted wave effect and the relativistic effect are found to play important roles in the low and high momentum regions, respectively.
基金Project supported by the National Natural Science Foundation of China(Grant No.11274149)the Program of Shenyang Key Laboratory of Optoelectronic Materials and Technology,China(Grant No.F12-254-1-00)
文摘This paper proposes a modified strong field approximation model for evaluating nondipole effects on the ionization of an atom in an intense laser field. The photoelectron longitudinal momentum distributions （PLMD） of a hydrogen-like atom exposed to a mid-infrared laser field is calculated. The theoretical results indicate an obvious asymmetry in the PLMD, and an offset of the PLMD peak appears in the opposite direction of the beam propagation due to nondipole effects. The peak offsets of the PLMD increased with the laser intensity, imposed by the initial state of the hydrogen-like atom.
基金Supported by the Fundamental Research Funds for the Central Universities under Grant No ZYGX2009X008
文摘Based on the generalized uncertainty principle with maximum momentum arid minimal length, we discuss the equation of state of ideal ultra-relativistic Fermi gases at zero temperature. Maximum momentum avoids the problem that the Fermi degenerate pressure blows up since the increase of the Fermi energy is not limited. Applying this equation of state to the Tolman-Oppenheimer Volkoff （TOV） equation, the quantum gravitational effects on the cores of compact stars are discussed. In the center of compact stars, we obtain the singularity-free solution of the metric component, gtt ～-（1 ＋ 0.2185×r^2）. By numerically solving the TOV equation, we find that quantum gravity plays an important role in the region r～10^4α0（△x）min. Current observed masses of neutron stars indicate that the dimensionless parameter α0 cannot exceed 10^19.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFA0402300).
文摘The outer valence electron momentum distributions of benzene are reinvestigated with theoretical calculations involving the vibrational effects.The results are compared with recent experimental measurements[Phys.Rev.A 98042705(2018)].The significant discrepancies between theories and experiments in previous works have now been interpreted quantitatively,indicating that the vibrational motion in benzene molecule has noticeable influence on its electron momentum distributions.
文摘The electronic structure of five conformers of 2-chloroethanol was studied by ab initio calculations at B3LYP and MP2 levels of theory with aug-cc-pVTZ basis set. The existing hydrogen bond and hyperconjugation effects on the stability of 2-chloroethanol conformers were discussed on the base of natural bond orbital analyses. The result exhibits that hyperconjugation is the main factor to determine the stability of conformers. Such effects on the electron wavefunctions of the highest-occupied molecular orbital （HOMO） of different conformers are demonstrated with electron momentum spectroscopy, exhibiting the obviously different symmetries of the HOMO wavefunctions in momentum space.
基金supported by the Maryland Center for Fundamental Physics,University of Maryland.
文摘Although equivalent in the infinite-momentum limit,large-momentum effective theory(LaMET)and short-distance operator product expansion(SDE)are 2 very different approaches to obtain parton distribution functions(PDFs)from coordinate-space correlation functions computed in a large-momentum proton through lattice quantum chromodynamics(QCD).LaMET implements a momentum-space expansion inΛ_(QCD)[/x(1-x)P^(z)]to directly calculate PDFs f(x)in a middle region of Bjorken x∈[x_(min)~Λ_(QCD)/xP^(z)x_(max)~1-x_(min)].SDE applies perturbative QCD at small Euclidean distances z to extract a range[0,λ_(max)]of leading-twist correlations,h(λ=zP^(z)),corresponding to the Fourier transformation of PDFs.An incomplete leading-twist correlation from SDE cannot be readily converted to a momentum-space distribution,and solving its constraints on the PDFs(or the so-called"inverse problem")involves phenomenological modeling of the missing information beyondλ_(max)and has no systematic control of errors.I argue that the best use of short-distance correlations is to constrain the PDFs in the LaMET-complementary regions:x∈[0,x_(min)]and[x_(max),1]through expected end-point asymptotics,and use the results of the pion valence quark distribution from the ANL/BNL collaboration to demonstrate how this can be done.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11961131008,11725416,and 11574010)the National Key Research and Development Program of China(Grant No.2018YFA0306302)
文摘In this review,we will focus on recent progress on the investigations of nondipole effects in few-electron atoms and molecules interacting with light fields.We first briefly survey several popular theoretical methods and relevant concepts in strong field and attosecond physics beyond the dipole approximation.Physical phenomena stemming from the breakdown of the dipole approximation are then discussed in various topics,including the radiation pressure and photon-momentum transfer,the atomic stabilization,the dynamic interference,and the high-order harmonic generation.Whenever available,the corresponding experimental observations of these nondipole effects are also introduced respectively in each topics.
文摘For the traditional photonic crystal fibers with circular air holes, rectangular air holes are added to the fiber cladding. The periodic arrangement of the inner rectangular air holes allows the fiber structure to better match the annular mode field distribution of the vortex beam. The fiber structure was analyzed and calculated by COMSOL Multiphysics 5.4 finite element software, and the characteristics of fiber were analyzed, such as the dispersion, confinement loss, effective mode area and nonlinear coefficient. The results reveal that the photonic crystal fiber structure capable of carrying 50 orbital angular momentum (OAM) modes at the wavelength of 1.15 to 2.0 μm (850 nm). The effective refractive index difference Δneff between vector modes can reach 1 × 10-3, and larger difference can effectively separate the vector modes and improve the transmission performance of OAM modes. Moreover, the fiber has good performance, such as flat dispersion distribution of the low-order modes, low confinement loss below 10-9 dB·m-1, large effective mode field area and small nonlinear coefficient in the 850 nm wavelength range. Therefore, this fiber structure can be applied to the high-capacity communication system of fiber multiplexing OAM. In addition, the good characteristics of this fiber structure are of great significance for the transmission of vortex beam in fiber.
文摘A simplified one-dimensional barotropic vorticity equation is used to study the influences of the vorticity and the momentum source on the large scale wave. Both vorticity source and momentum source can cause the formation of the large scale wave, but the former can produce large scale wave only under the condition that there is apparent basic flow acting on it, while the latter can produce the large scale wave even when tends to be zero. Furthermore, the amplitude of steady wave caused by the former is proportional to , while the amplitude caused by the latter has no relation to , instead it depends only on the magnitude of the perturbation of momentum.
基金Project supported by the State Key Program of Basic Research of China（Grant No G2000077400）, the Major program of the National Natural Science Foundation of China （Grant Nos 10435080 and 105350101）, the National Natural Science Foundation of China （Grant Nos 10447006, 10575075, 10125521 and 10447113）, the Knowledge Innovation Program of the Chinese Academy of Sciences （Grant No KJCX2-SW-N02）, Jiangsu Planned Projects for Postdoctoral Research Funds and China Postdoctoral Science Foundation.
文摘An isospin-dependent quantum molecular dynamical model （IQMD） is developed, with the isospin degree of freedom in the momentum-dependent interaction（MDI） included in IQMD, to obtain an isospin- and momentum-dependent interaction （IMDI） in IQMD. We investigate the effect of IMDI on the isospin fractionation ratio and its dynamical mechanism in the intermediate energy heavy ion collisions. It is found that the IMDI induces the significant reductions in the isospin fractionation ratio for all of beam energies, impact parameters, neutron-proton ratios and mass number of colliding systems. However, the strong dependence of isospin fractionation ratio on the symmetrical potential is preserved, with the isospin degree of freedom included in the MDI, i.e. the isospin fractionation ratio is still a good probe for extracting the information about the equation of state of isospin asymmetrical nuclear matter.
基金supported by the National Natural Science Foundation of China(Grant Nos.11074144,10874097,and 10704046)the Specialized Research Fund for the Doctoral Program of Higher Education,China(Grant No.20070003146)
文摘The binding energy spectra and the momentum distributions of the outer valence orbitals of W（CO）6 have been studied by using electron momentum spectroscopy as well as non-relativistic, scalar relativistic and spin-orbital relativistic DFT-B3LYP calculations. The experimental momentum profiles of the outer valence orbitals obtained with the impact energies of 1200 eV and 2400 eV were compared with various theoretical calculation results. The relativistic calculations could provide better descriptions for the experimental momentum distributions than the non-relativistic ones. Moreover, a new ordering of orbitals 10tlu, 3t2g, and 7eg, i.e., 10t_lu 〈 3t_2g 〈7e_g 〈10a_lg, is established in this work.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 19854002, 19774037 and 10274040） and the Research Fund for the Doctoral Program Foundation of Institution of Higher Education of China （Grant No 1999000327）.
文摘The first electronic structural study of the complete valence shell binding energy spectra of the antimicrobial agent diacetyl, encompassing both the outer and inner valence regions, is reported. The binding energy spectra as well as the individual orbital momentum profiles have been measured by using a high resolution （e, 2e） electron momentum spectrometer （EMS） at an impact energy of 1200eV plus the binding energy, and using symmetric noncoplanar kinematics. The experimental orbital electron momentum profiles are compared with self-consistent field （SCF） theoretical profiles calculated using the Hartree-Fock approximation and Density Functional theory predictions in the target Kohn-Sham approximation which includes some treatment of correlation via the exchange and correlation potentials with a range of basis sets. The pole strengths of the main ionization peaks from the inner valence orbitals are estimated.
文摘In recent years, digital investment portfolios have become a significant area of interest in the field of machine learning. To tackle the issue of neglecting the momentum effect in risk asset prices within the follow-the-winner strategy and to evaluate the significance of this effect, a novel measure of risk asset price momentum trend is introduced for online investment portfolio research. Firstly, a novel approach is introduced to quantify the momentum trend effect, which is determined by the product of the slope of the linear regression model and the absolute value of the linear correlation coefficient. Secondly, a new investment portfolio optimization problem is established based on the prediction of future returns. Thirdly, the Lagrange multiplier method is used to obtain the analytical solution of the optimization model, and the soft projection optimization algorithm is used to map the analytical solution to obtain the investment portfolio of the model. Finally, experiments are conducted on five benchmark datasets and compared with popular investment portfolio algorithms. The empirical findings indicate that the algorithm we are introduced is capable of generating higher investment returns, thereby establishing its efficacy for the management of the online investment portfolios.
文摘The concept of the effective mass in crystals shows that the electron mass is affected by the crystal field and was experimentally verified. A useful expression for effective mass was obtained. Unfortunately this expression showed that the effective mass vanishes in the ab-sence of the external field. This is in conflict with observations which show that it reduces to the ordinary mass. To cure this defect a new model is developed assuming the existence of vacuum force as verified experimentally as shown by Casimir effect. Using Newton’s second law and the quantum expression of momentum, useful expressions were found. The same expression was found using generalized special relativity. Strikingly the three models reduced to the conventional one in the absence of vacuum, they also reduced to the ordinary electron mass in the absence of all forces.
文摘By analyzing the Einstein-box thought experiment with the principle of relativity, it is shown that Abraham’s light momentum and energy in a medium cannot constitute a Lorentz four-vector, and they consequentially break global momentum and energy conservation laws. In contrast, Minkowski’s momentum and energy always constitute a Lorentz four-vector no matter whether in a medium or in vacuum, and the Minkowski’s momentum is the unique correct light momentum. A momentum-associated photon mass in a medium is exposed, which explains why only the Abraham’s momentum is derived in the traditional “center-of-mass-energy” approach. The EM boundary-condition matching approach, combined with Einstein light-quantum hypothesis, is proposed to analyze this thought experiment, and it is found for the first time that only from Maxwell equations without resort to the relativity, the correctness of light momentum definitions cannot be identified. Optical pulling effect is studied as well.
