Showing papers by "T.T.S. Kuo published in 2010"

Unitarity potentials and neutron matter at the unitary limit

Abstract: We study the equation of state of neutron matter using a family of unitarity potentials, all of which are constructed to have infinite ${}^{1}{S}_{0}$ scattering lengths ${a}_{s}$. For such a system, a quantity of much interest is the ratio $\ensuremath{\xi}={E}_{0}/{E}_{0}^{\mathrm{free}}$, where ${E}_{0}$ is the true ground-state energy of the system and ${E}_{0}^{\mathrm{free}}$ is that for the noninteracting system. In the limit of ${a}_{s}\ensuremath{\rightarrow}\ifmmode\pm\else\textpm\fi{}\ensuremath{\infty}$, often referred to as the unitary limit, this ratio is expected to approach a universal constant, namely $\ensuremath{\xi}~0.44(1)$. In the present work we calculate this ratio $\ensuremath{\xi}$ using a family of hard-core square-well potentials whose ${a}_{s}$ can be exactly obtained, thus enabling us to have many potentials of different ranges and strengths, all with infinite ${a}_{s}$. We have also calculated $\ensuremath{\xi}$ using a unitarity CDBonn potential obtained by slightly scaling its meson parameters. The ratios $\ensuremath{\xi}$ given by these different unitarity potentials are all close to each other and also remarkably close to 0.44, suggesting that the above ratio $\ensuremath{\xi}$ is indifferent to the details of the underlying interactions as long as they have infinite scattering length. A sum-rule and scaling constraint for the renormalized low-momentum interaction in neutron matter at the unitary limit is studied. The importance of pairing in our all-order ring diagram and model-space HF calculations of neutron matter is discussed.

Fermionic-bosonic couplings in a weakly deformed odd-mass nucleus, 41 93 Nb

Abstract: A comprehensive level scheme of $^{93}\mathrm{Nb}$ below 2 MeV has been constructed from information obtained with the $^{93}\mathrm{Nb}$($n,{n}^{\ensuremath{'}}\ensuremath{\gamma}$) and the $^{94}\mathrm{Zr}$($p,2n\ensuremath{\gamma}\ensuremath{\gamma}$)$^{93}\mathrm{Nb}$ reactions. Branching ratios, lifetimes, transition multipolarities, and spin assignments have been determined. From $M1$ and $E2$ strengths, fermionic-bosonic excitations of isoscalar and isovector characters have been identified from the weak couplings of the $\ensuremath{\pi}1{g}_{9/2}\ensuremath{\bigotimes}{}_{40}^{92}\mathrm{Zr}$ and $\ensuremath{\pi}2{p}_{1/2}^{\ensuremath{-}1}\ensuremath{\bigotimes}{}_{42}^{94}\mathrm{Mo}$ configurations. A microscopic interpretation of such excitations is obtained from shell-model calculations, which use low-momentum effective interactions.