Speaker
Dr
Matthias Hempel
(Basel University)
Description
Cluster formation is a fundamental aspect of the equation of state (EOS) of
warm and dense nuclear matter such as can be found in supernovae (SNe). Similar
matter can be studied in heavy-ion collisions (HIC). We use the experimental
data of Qin et al. [Phys. Rev. Lett. 108, 172701 (2012)] to test calculations
of cluster formation and the role of in-medium modifications of cluster
properties in SN EOSs. For the comparison between theory and experiment we use
chemical equilibrium constants as the main observables. This reduces some of
the systematic uncertainties and allows deviations from ideal gas behavior to
be identified clearly. In the analysis, we carefully account for the
differences between matter in SNe and HICs. We find that, at the lowest
densities, the experiment and all theoretical models are consistent with the
ideal gas behavior. At higher densities ideal behavior is clearly ruled out and
interaction effects have to be considered. The contributions of continuum
correlations are of relevance in the virial expansion and remain a difficult
problem to solve at higher densities. We conclude that at the densities and
temperatures discussed mean-field interactions of nucleons, inclusion of all
relevant light clusters, and a suppression mechanism of clusters at high
densities have to be incorporated in the SN EOS.
Primary author
Dr
Matthias Hempel
(Basel University)
Co-authors
Prof.
Gerd Röpke
(Rostock University)
Prof.
Joseph Natowitz
(Texas A&M)
Dr
Kris Hagel
(Texas A&M)
Dr
Stefan Typel
(GSI)
