ترغب بنشر مسار تعليمي؟ اضغط هنا

Analytic approach to nuclear rotational states: The role of spin - A minimal model -

88   0   0.0 ( 0 )
 نشر من قبل Wolfgang Bentz
 تاريخ النشر 2013
  مجال البحث
والبحث باللغة English




اسأل ChatGPT حول البحث

We use a simple field theory model to investigate the role of the nucleon spin for the magnetic sum rules associated with the low-lying collective scissors mode in deformed nuclei. Various constraints from rotational symmetry are elucidated and discussed. We put special emphasis on the coupling of the spin part of the M1 operator to the low lying collective modes, and investigate how this coupling changes the sum rules.



قيم البحث

اقرأ أيضاً

360 - W. Bentz , A. Arima , J. Enders 2011
The consequences of the spontaneous breaking of rotational symmetry are investigated in a field theory model for deformed nuclei, based on simple separable interactions. The crucial role of the Ward-Takahashi identities to describe the rotational sta tes is emphasized. We show explicitly how the rotor picture emerges from the isoscalar Goldstone modes, and how the two-rotor model emerges from the isovector scissors modes. As an application of the formalism, we discuss the M1 sum rules in deformed nuclei, and make connection to empirical information.
216 - W. Zuo , U. Lombardo , C.W. Shen 2002
The equations of state of spin-polarized nuclear matter and pure neutron matter are studied in the framework of the Brueckner-Hartree-Fock theory including a three-body force. The energy per nucleon $E_A(delta)$ calculated in the full range of spin p olarization ${delta} = frac{rho_{uparrow}-rho_{downarrow}}{rho}$ for symmetric nuclear matter and pure neutron matter fulfills a parabolic law. In both cases the spin-symmetry energy is calculated as a function of the baryonic density along with the related quantities such as the magnetic susceptibility and the Landau parameter $G_0$. The main effect of the three-body force is to strongly reduce the degenerate Fermi gas magnetic susceptibility even more than the value with only two body force. The EOS is monotonically increasing with the density for all spin-aligned configurations studied here so that no any signature is found for a spontaneous transition to a ferromagnetic state.
We present a minimal nuclear energy density functional (NEDF) called SeaLL1 that has the smallest number of possible phenomenological parameters to date. SeaLL1 is defined by 7 significant phenomenological parameters, each related to a specific nucle ar property. It describes the nuclear masses of even-even nuclei with a mean energy error of 0.97 MeV and a standard deviation 1.46 MeV, two-neutron and two-proton separation energies with r.m.s. errors of 0.69 MeV and 0.59 MeV respectively, and the charge radii of 345 even-even nuclei with a mean error $epsilon_r=$0.022 fm and a standard deviation $sigma_r=$0.025 fm. SeaLL1 incorporates constraints on the EoS of pure neutron matter from quantum Monte Carlo calculations with chiral effective field theory two-body (NN) interactions at N3LO level and three-body (NNN) interactions at the N2LO level. Two of the seven parameters are related to the saturation density and the energy per particle of the homogeneous symmetric nuclear matter, one is related to the nuclear surface tension, two are related to the symmetry energy and its density dependence, one is related to the strength of the spin-orbit interaction, and one is the coupling constant of the pairing interaction. We identify additional phenomenological parameters that have little effect on ground-state properties, but can be used to fine-tune features such as the Thomas-Reiche-Kuhn sum rule, the excitation energy of the giant dipole and Gamow-Teller resonances, the static dipole electric polarizability, and the neutron skin thickness.
54 - H. Nakada , T. Sebe , K. Muto 1996
We discuss two conditions needed for correct computation of $2 u betabeta$ nuclear matrix-elements within the realistic shell-model framework. An algorithm in which intermediate states are treated based on Whiteheads moment method is inspected, by ta king examples of the double GT$^+$ transitions $mbox{$^{36}$Ar}rightarrowmbox{$^{36}$S}$, $mbox{$^{54}$Fe}rightarrowmbox{$^{54}$Cr}$ and $mbox{$^{58}$Ni} rightarrowmbox{$^{58}$Fe}$. This algorithm yields rapid convergence on the $2 ubetabeta$ matrix-elements, even when neither relevant GT$^+$ nor GT$^-$ strength distribution is convergent. A significant role of the shell structure is pointed out, which makes the $2 ubeta beta$ matrix-elements highly dominated by the low-lying intermediate states. Experimental information of the low-lying GT$^pm$ strengths is strongly desired. Half-lives of $T^{2 u}_{1/2}({rm EC}/{rm EC}; mbox{$^{36}$Ar}rightarrowmbox{$^{36}$S})=1.7times 10^{29}mbox{yr}$, $T^{2 u}_{1/2}({rm EC}/{rm EC};mbox{$^{54}$Fe}rightarrow mbox{$^{54}$Cr})=1.5times 10^{27}mbox{yr}$,$T^{2 u}_{1/2}({rm EC} /{rm EC};mbox{$^{58}$Ni}rightarrowmbox{$^{58}$Fe})=6.1times 10^{24}mbox{yr}$and $T^{2 u}_{1/2}(beta^+/{rm EC};mbox{$^{58}$Ni} rightarrowmbox{$^{58}$Fe})=8.6times 10^{25}mbox{yr}$ are obtained from the present realistic shell-model calculation of the nuclear matrix-elements.
We present a nucleus-dependent valence-space approach for calculating ground and excited states of nuclei, which generalizes the shell-model in-medium similarity renormalization group to an ensemble reference with fractionally filled orbitals. Becaus e the ensemble is used only as a reference, and not to represent physical states, no symmetry restoration is required. This allows us to capture 3N forces among valence nucleons with a valence-space Hamiltonian specifically targeted to each nucleus of interest. Predicted ground-state energies from carbon through nickel agree with results of other large-space ab initio methods, generally to the 1% level. In addition, we show that this new approach is required in order to obtain convergence for nuclei in the upper $p$ and $sd$ shells. Finally, we address the $1^+$/$3^+$ ground-state inversion problem in $^{22}text{Na}$ and $^{46}text{V}$. This approach extends the reach of ab initio nuclear structure calculations to essentially all light- and medium-mass nuclei.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا