2,001 research outputs found

    Towards understanding the probability of 0+0^+ ground states in even-even many-body systems

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    For single-jj shells with j=7/2,9/2j={7/2}, {9/2} and 11/2, we relate the large probability of I+I^+ ground states to the largest (smallest) coefficients αI(vβ)J=<nvβI∣\alpha^J_{I(v \beta)} = <nv \beta I | AJ†⋅AJ∣nvβI>A^{J \dagger} \cdot A^J | n v\beta I>, where nn is the particle number, vv is the seniority, β\beta is an additional quantum number, and II is the angular momentum of the state. Interesting regularities of the probabilities of I+I^+ ground states are noticed and discussed for 4-particle systems. Several counter examples of the 0+0^+ ground state (0GS) predominance are noticed for the first time.Comment: 5 pages, 1 figure. Phys. Rev. C64, in pres

    Energy Centroids of Spin II States by Random Two-body Interactions

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    In this paper we study the behavior of energy centroids (denoted as EIˉ\bar{E_I}) of spin II states in the presence of random two-body interactions, for systems ranging from very simple systems (e.g. single-jj shell for very small jj) to very complicated systems (e.g., many-jj shells with different parities and with isospin degree of freedom). Regularities of EIˉ\bar{E_I}'s discussed in terms of the so-called geometric chaoticity (or quasi-randomness of two-body coefficients of fractional parentage) in earlier works are found to hold even for very simple systems in which one cannot assume the geometric chaoticity. It is shown that the inclusion of isospin and parity does not "break" the regularities of EIˉ\bar{E_I}'s.Comment: four figures. to appear in Physical Review

    Perovskite Manganites Hosting Versatile Multiferroic Phases with Symmetric and Antisymmetric Exchange Strictions

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    Complete magnetoelectric (ME) phase diagrams of orthorhombic RRMnO3_{3} with and without magnetic moments on the RR ions have been established. Three kinds of multiferroic ground states, the abab-cycloidal, the bcbc-cycloidal, and the collinear EE-type phases, have been identified by the distinct ME responses. The electric polarization of the EE-type phase dominated by the symmetric spin exchange (bmSicdotbmSjbm{S}_{i} cdot bm{S}_{j}) is more than 10 times as large as that of the bcbc-cycloidal phase dominated by the antisymmetric one (bmSitimesbmSjbm{S}_{i} times bm{S}_{j}), and the ME response is enhanced near the bicritical phase boundary between these multiferroic phases of different origins. These findings will provide an important clue for the development of the magnetically induced multiferroics.Comment: 5 pages, 3 figure

    Lattice-form dependent orbital shape and charge disproportionation in charge- and orbital-ordered manganites

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    The orbital shapes and charge disproportionations at nominal Mn3+^{3+} and Mn4+^{4+} sites for the charge- and orbital-ordered phases have been studied on half-doped manganites Pr(Sr0.1_{0.1}Ca0.9_{0.9})2_2Mn2_2O7_7 and Eu0.5_{0.5}Ca1.5_{1.5}MnO4_4 with double-layer and single-layer Mn-O networks, respectively, by means of x-ray structural analyses, in comparison with Pr0.5_{0.5}Ca0.5_{0.5}MnO3_3 with the pseudo cubic network. In a single-layer Eu0.5_{0.5}Ca1.5_{1.5}MnO4_4 system, the (y2−z2y^2-z^2)/(z2−x2z^2-x^2)-type orbital shape is observed, while the (3y2−r23y^2-r^2)/(3x2−r23x^2-r^2)-type orbital shape in a pseudo cubic Pr0.5_{0.5}Ca0.5_{0.5}MnO3_3 system. In a double-layer Pr(Sr0.1_{0.1}Ca0.9_{0.9})2_2Mn2_2O7_7 system, the orbital shape is found to undergo a large change upon thermally induced rotation of orbital stripe. Furthermore, clear charge disproportionation is observed for the pseudo cubic and double-layer systems, while not in the single-layer system. These results indicate that the orbital shape and charge disproportionation are sensitive to the dimension of Mn-O network.Comment: 12 page, 5 figures, 11 table

    Classification of states of single-jj fermions with JJ-pairing interaction

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    In this paper we show that a system of three fermions is exactly solvable for the case of a single-jj in the presence of an angular momentum-JJ pairing interaction. On the basis of the solutions for this system, we obtain new sum rules for six-jj symbols. It is also found that the "non-integer" eigenvalues of three fermions with angular momentum II around the maximum appear as "non-integer" eigenvalues of four fermions when II is around (or larger than) JmaxJ_{\rm max} and the Hamiltonian contains only an interaction between pairs of fermions coupled to spin J=Jmax=2j−1J=J_{\rm max}=2j-1. This pattern is also found in five and six fermion systems. A boson system with spin ll exhibits a similar pattern.Comment: to be published in Physical Review

    General pairing interactions and pair truncation approximations for fermions in a single-j shell

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    We investigate Hamiltonians with attractive interactions between pairs of fermions coupled to angular momentum J. We show that pairs with spin J are reasonable building blocks for the low-lying states. For systems with only a J = Jmax pairing interaction, eigenvalues are found to be approximately integers for a large array of states, in particular for those with total angular momenta I le 2j. For I=0 eigenstates of four fermions in a single-j shell we show that there is only one non-zero eigenvalue. We address these observations using the nucleon pair approximation of the shell model and relate our results with a number of currently interesting problems.Comment: a latex text file and 2 figures, to be publishe

    Residual proton-neutron interactions and the NpNnN_{\rm p} N_{\rm n} scheme

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    We investigate the correlation between integrated proton-neutron interactions obtained by using the up-to-date experimental data of binding energies and the NpNnN_{\rm p} N_{\rm n}, the product of valence proton number and valence neutron number with respect to the nearest doubly closed nucleus. We make corrections on a previously suggested formula for the integrated proton-neutron interaction. Our results demonstrate a nice, nearly linear, correlation between the integrated p-n interaction and NpNnN_{\rm p} N_{\rm n}, which provides us with a firm foundation of the applicability of the NpNnN_{\rm p} N_{\rm n} scheme to nuclei far from the stability line.Comment: four pages, three figures, Physical Review C, in pres

    Nuclear Mass Dependence of Chaotic Dynamics in Ginocchio Model

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    The chaotic dynamics in nuclear collective motion is studied in the framework of a schematic shell model which has only monopole and quadrupole degrees of freedom. The model is shown to reproduce the experimentally observed global trend toward less chaotic motion in heavier nuclei. The relation between current approach and the earlier studies with bosonic models is discussed.Comment: 11 Page REVTeX file, 2 postscript figures, uuencode
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