110,770 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 | AJAJnvβI>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

    Simulating emergent urban form: desakota in China

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    We propose that the emergent phenomenon know as ?desakota?, the rapidurbanization of densely populated rural populations in the newlydeveloped world, particularly China, can be simulated using agent-basedmodels which combine both local and global features. We argue thatdeskota represents a surprising and unusual form of urbanization wellmatchedto processes of land development that are driven from the bottomup but moderated by the higher-level macro economy. We develop asimple logic which links local household reform to global urban reform,translating these ideas into a model structure which reflects these twoscales. Our model first determines the rate of growth of different spatialaggregates using linear statistical analysis. It then allocates this growth tothe local level using developer agents who determine the transformation ormutation of rural households to urban pursuits based on local land costs,accessibilities, and growth management practices. The model is applied todesakota development in the Suzhou region between 1990 and 2000. Weshow how the global rates of change predicted at the township level in theWuxian City region surrounding Suzhou are tempered by localtransformations of rural to urban land uses which we predict using cellularautomata rules. The model, which is implemented in the RePast 3software, is validated using a blend of data taken from remote sensing andgovernment statistical sources. It represents an example of generativesocial science that fuses plausible behavior with formalized logics matchedagainst empirical evidence, essential in showing how novel patterns ofurbanization such as desakota emerge

    Spherical to deformed shape transition in the nucleon-pair shell model

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    A study of the shape transition from spherical to axially deformed nuclei in the even Ce isotopes using the nucleon-pair approximation of the shell model is reported. As long as the structure of the dominant collective pairs is determined using a microscopic framework appropriate to deformed nuclei, the model is able to produce a shape transition. However, the resulting transition is too rapid, with nuclei that should be transitional being fairly well deformed, perhaps reflecting the need to maintain several pairs with each angular momentum.Comment: 7 pages, 5 figure