A method for the treatment of the neutron-proton(np) isovector pairing correlations at finite temperature is developed within the path integral formalism.It generalizes the recently proposed model using a similar appr...A method for the treatment of the neutron-proton(np) isovector pairing correlations at finite temperature is developed within the path integral formalism.It generalizes the recently proposed model using a similar approach for pairing between like-particles.The pairing terms in the total Hamiltonian are expressed in a square form to facilitate the use of the Hubbard-Stratonovitch transformation.The expression for the partition function of the system is then established.The gap equations,as well as the expressions for the energy,entropy,and heat capacity of the system are deduced.In a first step,the formalism is numerically applied to the schematic Richardson model.In a second step,the method is applied to nuclei with N=Z using the single-particle energies of a deformed Woods-Saxon mean-field.The variations in the gap parameters,excitation energy,and heat capacity are studied as functions of the temperature.We show that the overall behavior of these quantities is similar to their homologues in the standard FTBCS model.We note in particular the existence of critical temperatures beyond which the pairing vanishes.Moreover,in the framework of the present approach,the pairing effects appear to persist beyond the critical temperatures predicted by the FTBCS model for pairing between like-particles or its generalization for np pairing.展开更多
In our previous study, the deduced Langevin equation has been applied to investigate the isoscalar giant monopole resonance. In the current study, the framework is extended to study the isovector giant dipole resonanc...In our previous study, the deduced Langevin equation has been applied to investigate the isoscalar giant monopole resonance. In the current study, the framework is extended to study the isovector giant dipole resonance(IVGDR). The potential well in the IVGDR is calculated by separating the neutron and proton densities based on the Hartree-Fock ground state. Subsequently, the Langevin equation is solved self-consistently, resulting in the centroid energy of the IVGDR without width. The symmetry energy around the density of 0.02 fm^-3 contributes the most to the potential well in the IVGDR. By comparison with the updated experimental data of IVGDR energies in spherical nuclei, the calculations within 37 sets of Skyrme functionals suggest the symmetry energy to be in the range of 8.13-9.54 MeV at a density of 0.02 fm^-3.展开更多
The competition of isovector and isoscalar pairing in A=18 and 20 even-even N≈Z nuclei is analyzed in the framework of the mean-field plus the dynamic quadurpole-quadurpole, pairing and particle-hole interactions, wh...The competition of isovector and isoscalar pairing in A=18 and 20 even-even N≈Z nuclei is analyzed in the framework of the mean-field plus the dynamic quadurpole-quadurpole, pairing and particle-hole interactions, whose Hamiltonian is diagonalized in the basis U(24) ?(U(6) ? S U(3) ? S O(3))■(U(4) ? S US(2)■ S UT(2)) in the L = 0 configuration subspace. Besides the pairing interaction, it is observed that the quadurpole-quadurpole and particlehole interactions also play a significant role in determining the relative positions of low-lying excited 0^+ and 1^+ levels and their energy gaps, which can result in the ground state first-order quantum phase transition from J = 0 to J = 1.The strengths of the isovector and isoscalar pairing interactions in these even-even nuclei are estimated with respect to the energy gap and the total contribution to the binding energy. Most importantly, it is shown that although the mechanism of the particle-hole contribution to the binding energy is different, it is indirectly related to the Wigner term in the binding energy.展开更多
With the inclusion of the isovector scalar channel in the meson-nucleon couplings, taking DD-MEδ as an effective interaction, the moments of inertia of neutron stars possessing various stellar masses are studied with...With the inclusion of the isovector scalar channel in the meson-nucleon couplings, taking DD-MEδ as an effective interaction, the moments of inertia of neutron stars possessing various stellar masses are studied within the density dependent relativistic mean field （RMF） theory. The isovector scalar channel contributes to the softening of the neutron-star matter equation of state （EOS） and therefore the reduction of the maximum mass and radius of neutron stars. Smaller values of the total moment of inertia 1 and the crustal moment of inertia AI are then obtained in DD-ME~ via numerical procedure in comparison with those in other selected RMF functionals. In addition, the involvement of the isovector scalar channel lowers the thickness of the neutron star crust and its mass fi＇action as well. The sensitivity to both the crustal mass and stellar radius causes the crustal moment of inertia to be more obviously reduced than the total one, eventually leading to a suppression on the fraction of crustal moment of inertia △I/I in DD-MFδ. The results indicate the crustal moment of inertia as a more sensitive probe of the neutron-star matter EOS than the total one, and demonstrate that the isovector scalar meson-nucleon couplings in the RMF theory could exert influence over the physics of pulsar glitches.展开更多
We study some properties of the simplest neutron stars （NSs） in the Glendenning Moszkowski （GM） model, the hybrid derivative coupling （HD） model and the Zimanyi Moszkowski （ZM） model in the framework of relati...We study some properties of the simplest neutron stars （NSs） in the Glendenning Moszkowski （GM） model, the hybrid derivative coupling （HD） model and the Zimanyi Moszkowski （ZM） model in the framework of relativistic mean field （RMF） theory with and without the interaction by exchanging the ^-meson. We show that the maximal mass of the NSs becomes smaller, but the redshift becomes larger from the GM model to the HD model, then to the ZM model. The interaction with the 6-meson exchange enlarges the maximal mass of neutron stars, increases the relative population of charged particles （proton, electron and muon） and descends the relative population of neutron.展开更多
The isovector giant dipole resonance in Ca isotopes is investigated in the framework of the fully consistent relativistic random phase approximation. The calculations are performed in an effective Lagrangian with a pa...The isovector giant dipole resonance in Ca isotopes is investigated in the framework of the fully consistent relativistic random phase approximation. The calculations are performed in an effective Lagrangian with a parameter set , which was proposed for satisfactorily describing nuclear ground state properties. It is found that a soft isovector dipole mode for Ca isotopes near drip lines exists at energy around . The soft dipole states are mainly due to the excitation of the weakly bound and pure neutron (proton) states near Fermi surface as well as the correlation of isoscalar and isovector operators. For nuclei with the extreme value of , the contributions of isoscalar mesons in the isovector mode play a non-negligible role.展开更多
In the framework of the relativistic mean field theory, the effects of the δ meson on the direct Urca （DURCA） processes are investigated. In a neutron star, the DURCA processes involving nucleons, A and - can ta...In the framework of the relativistic mean field theory, the effects of the δ meson on the direct Urca （DURCA） processes are investigated. In a neutron star, the DURCA processes involving nucleons, A and - can take place while the process involving the 0 can not. With the inclusion of the δ meson, the threshold densities for the DURCA processes become lower. With the δ included, the threshold neutron star mass for the DURCA process among nucleons and electrons becomes smaller while the threshold masses for the processes involving hyperons become larger. When the δ meson is included, the total neutrino emissivity remarkably increases in the density range of 0.32-0.41 fm-3. The total neutrino luminosity increases with the neutron star mass first and then decreases. The neutrino luminosity gets larger with the inclusion of the δ meson. The cooling of the EXO0748-676 is sensitive to the isovector scalar interaction.展开更多
In the present work,we study the effect of the isovector scalar meson a_(0)(980)(also calledδ)to the asymmetric matter properties by constructing a parity doublet model with including the a_(0)(980)meson based on the...In the present work,we study the effect of the isovector scalar meson a_(0)(980)(also calledδ)to the asymmetric matter properties by constructing a parity doublet model with including the a_(0)(980)meson based on the approximate chiral U(2)_(L)×U(2)_(R)symmetry.The effect of a_(0)(980)to the properties of symmetric matter such as symmetry energy S(n_(B)),symmetry incompressibility K_(sym),symmetry skewness Q_(sym)is investigated.We find that,a_(0)(980)meson has significant effect to these nuclear matter properties especially when the chiral invariant mass of nucleon m_(0)is small.We also study the effect of the a_(0)(980)meson to the neutron star(NS)properties and find that it increase the radius of NSs,especially those having intermediate mass.Finally,we further constrain the value of the chiral invariant mass of the nucleon to 640 MeV≲m_(0)≲860 MeV for L_(0)=57:7MeV by comparing with the recent accepted value of K_(sym)and neutron star(NS)observational data.展开更多
文摘A method for the treatment of the neutron-proton(np) isovector pairing correlations at finite temperature is developed within the path integral formalism.It generalizes the recently proposed model using a similar approach for pairing between like-particles.The pairing terms in the total Hamiltonian are expressed in a square form to facilitate the use of the Hubbard-Stratonovitch transformation.The expression for the partition function of the system is then established.The gap equations,as well as the expressions for the energy,entropy,and heat capacity of the system are deduced.In a first step,the formalism is numerically applied to the schematic Richardson model.In a second step,the method is applied to nuclei with N=Z using the single-particle energies of a deformed Woods-Saxon mean-field.The variations in the gap parameters,excitation energy,and heat capacity are studied as functions of the temperature.We show that the overall behavior of these quantities is similar to their homologues in the standard FTBCS model.We note in particular the existence of critical temperatures beyond which the pairing vanishes.Moreover,in the framework of the present approach,the pairing effects appear to persist beyond the critical temperatures predicted by the FTBCS model for pairing between like-particles or its generalization for np pairing.
基金Supported by the National Natural Science Foundation of China(11875328)
文摘In our previous study, the deduced Langevin equation has been applied to investigate the isoscalar giant monopole resonance. In the current study, the framework is extended to study the isovector giant dipole resonance(IVGDR). The potential well in the IVGDR is calculated by separating the neutron and proton densities based on the Hartree-Fock ground state. Subsequently, the Langevin equation is solved self-consistently, resulting in the centroid energy of the IVGDR without width. The symmetry energy around the density of 0.02 fm^-3 contributes the most to the potential well in the IVGDR. By comparison with the updated experimental data of IVGDR energies in spherical nuclei, the calculations within 37 sets of Skyrme functionals suggest the symmetry energy to be in the range of 8.13-9.54 MeV at a density of 0.02 fm^-3.
基金Supported by the National Natural Science Foundation of China(11675071 and 11375080)the U.S.National Science Foundation(OIA-1738287 and ACI-1713690)+2 种基金U.S.Department of Energy(DE-SC0005248)the Southeastern Universities Research Association,the China-U.S.Theory Institute for Physics with Exotic Nuclei(CUSTIPEN)(DE-SC0009971)the LSU-LNNU joint research program(9961)
文摘The competition of isovector and isoscalar pairing in A=18 and 20 even-even N≈Z nuclei is analyzed in the framework of the mean-field plus the dynamic quadurpole-quadurpole, pairing and particle-hole interactions, whose Hamiltonian is diagonalized in the basis U(24) ?(U(6) ? S U(3) ? S O(3))■(U(4) ? S US(2)■ S UT(2)) in the L = 0 configuration subspace. Besides the pairing interaction, it is observed that the quadurpole-quadurpole and particlehole interactions also play a significant role in determining the relative positions of low-lying excited 0^+ and 1^+ levels and their energy gaps, which can result in the ground state first-order quantum phase transition from J = 0 to J = 1.The strengths of the isovector and isoscalar pairing interactions in these even-even nuclei are estimated with respect to the energy gap and the total contribution to the binding energy. Most importantly, it is shown that although the mechanism of the particle-hole contribution to the binding energy is different, it is indirectly related to the Wigner term in the binding energy.
基金supported by the National Natural Science Foundation of China(Grant No.11375076)the Fundamental Research Funds for the Central Universities(Grant No.lzujbky-2016-30)
文摘With the inclusion of the isovector scalar channel in the meson-nucleon couplings, taking DD-MEδ as an effective interaction, the moments of inertia of neutron stars possessing various stellar masses are studied within the density dependent relativistic mean field （RMF） theory. The isovector scalar channel contributes to the softening of the neutron-star matter equation of state （EOS） and therefore the reduction of the maximum mass and radius of neutron stars. Smaller values of the total moment of inertia 1 and the crustal moment of inertia AI are then obtained in DD-ME~ via numerical procedure in comparison with those in other selected RMF functionals. In addition, the involvement of the isovector scalar channel lowers the thickness of the neutron star crust and its mass fi＇action as well. The sensitivity to both the crustal mass and stellar radius causes the crustal moment of inertia to be more obviously reduced than the total one, eventually leading to a suppression on the fraction of crustal moment of inertia △I/I in DD-MFδ. The results indicate the crustal moment of inertia as a more sensitive probe of the neutron-star matter EOS than the total one, and demonstrate that the isovector scalar meson-nucleon couplings in the RMF theory could exert influence over the physics of pulsar glitches.
基金Supported by the National Natural Science Foundation of China under contract Nos 10425521, 10575005 and 10675007, the National Basic Research Programme of China under Grant No G2007CB815000, the Ministry of Education of China under Grant No 305001, and the Research Fund for the Doctoral Programme of Higher Education of China under Grant No 20040001010.
文摘We study some properties of the simplest neutron stars （NSs） in the Glendenning Moszkowski （GM） model, the hybrid derivative coupling （HD） model and the Zimanyi Moszkowski （ZM） model in the framework of relativistic mean field （RMF） theory with and without the interaction by exchanging the ^-meson. We show that the maximal mass of the NSs becomes smaller, but the redshift becomes larger from the GM model to the HD model, then to the ZM model. The interaction with the 6-meson exchange enlarges the maximal mass of neutron stars, increases the relative population of charged particles （proton, electron and muon） and descends the relative population of neutron.
文摘The isovector giant dipole resonance in Ca isotopes is investigated in the framework of the fully consistent relativistic random phase approximation. The calculations are performed in an effective Lagrangian with a parameter set , which was proposed for satisfactorily describing nuclear ground state properties. It is found that a soft isovector dipole mode for Ca isotopes near drip lines exists at energy around . The soft dipole states are mainly due to the excitation of the weakly bound and pure neutron (proton) states near Fermi surface as well as the correlation of isoscalar and isovector operators. For nuclei with the extreme value of , the contributions of isoscalar mesons in the isovector mode play a non-negligible role.
基金Supported by National Natural Science Foundation of China (10675024,11075063)Natural Science Fundamental Research Project of Jiangsu Colleges and Universities (10KJB140002)
文摘In the framework of the relativistic mean field theory, the effects of the δ meson on the direct Urca （DURCA） processes are investigated. In a neutron star, the DURCA processes involving nucleons, A and - can take place while the process involving the 0 can not. With the inclusion of the δ meson, the threshold densities for the DURCA processes become lower. With the δ included, the threshold neutron star mass for the DURCA process among nucleons and electrons becomes smaller while the threshold masses for the processes involving hyperons become larger. When the δ meson is included, the total neutrino emissivity remarkably increases in the density range of 0.32-0.41 fm-3. The total neutrino luminosity increases with the neutron star mass first and then decreases. The neutrino luminosity gets larger with the inclusion of the δ meson. The cooling of the EXO0748-676 is sensitive to the isovector scalar interaction.
文摘In the present work,we study the effect of the isovector scalar meson a_(0)(980)(also calledδ)to the asymmetric matter properties by constructing a parity doublet model with including the a_(0)(980)meson based on the approximate chiral U(2)_(L)×U(2)_(R)symmetry.The effect of a_(0)(980)to the properties of symmetric matter such as symmetry energy S(n_(B)),symmetry incompressibility K_(sym),symmetry skewness Q_(sym)is investigated.We find that,a_(0)(980)meson has significant effect to these nuclear matter properties especially when the chiral invariant mass of nucleon m_(0)is small.We also study the effect of the a_(0)(980)meson to the neutron star(NS)properties and find that it increase the radius of NSs,especially those having intermediate mass.Finally,we further constrain the value of the chiral invariant mass of the nucleon to 640 MeV≲m_(0)≲860 MeV for L_(0)=57:7MeV by comparing with the recent accepted value of K_(sym)and neutron star(NS)observational data.
