3 research outputs found

    Double-Dipole Excitations in 40Ca

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    The double-dipole strength distribution in 40^{40}Ca is calculated microscopically within a model space of 1p1h - and 2p2h excitations. Anharmonic effects in the centroid energies of the 0+0^+- and 2+2^+ components are found to be small, in agreement with experimental observation. Firm conclusions about the spreading width cannot be drawn, as yet, due to computational limitations in the number of 2p2h states.Comment: 8 pages of LaTeX, two figures available at ftp://rsm1.physcis.uiuc.edu/pub/figs

    A Non-Perturbative Treatment of the Pion in the Linear Sigma-Model

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    Using a non-perturbative method based on the selfconsistent Quasi-particle Random-Phase Approximation (QRPA) we describe the properties of the pion in the linear σ\sigma-model. It is found that the pion is massless in the chiral limit, both at zero- and finite temperature, in accordance with Goldstone's theorem.Comment: To appear in Nucl.Phys. A, 16 pages, 2 Postscript figure
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