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Résumé |
Few-body universality connects the properties of systems that are governed by
interactions which generate large s-wave scattering lengths, $a_0$. In the first
part of this talk I will argue that several two-neutron halo nuclei could
display aspects of few-body universality. In particular, I will show
calculations of the two-neutron energy spectrum that is produced after rapid
removal of the core from several exotic nuclei. After appropriate rescaling
the resulting spectra are described by single curve, a result that is due to
the proximity of the neutron-neutron and core-neutron interactions to the
unitary limit $|a_0|\to \infty$. In the second part of the talk I will discuss ab initio
results for $^6$Li that were obtained using the No-Core Shell Model with
Continuum (NCSMC). The NCSMC calculations show a strong correlation between
the deuteron separation energy in $^6$Li and the Asymptotic Normalization
Coefficient of the alpha-deuteron component of its wave function. I will
argue that this correlation is not a universal one, but that it is due to a
factorization of long-distance and short-distance physics in $^6$Li, and that
this factorization can be exploited to make ab initio calculations of that
system more efficient.
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