Abstract
If a first-order phase transition separates nuclear and quark matter at large baryon density, an interface between these two phases has a nonzero surface tension. We calculate this surface tension within a nucleon-meson model for domain walls and bubbles. Various methods and approximations are discussed and compared, including a numerical evaluation of the spatial profile of the interface. We also compute the surface tension at the other first-order phase transitions of the model: the nuclear liquid-gas transition and, in the parameter regime where it exists, the direct transition from the vacuum to the (approximately) chirally symmetric phase. Identifying the chirally symmetric phase with quark matter - our model does not contain explicit quark degrees of freedom - we find maximal surface tensions of the vacuum-quark transition $\Sigma_{\rm VQ}\sim 15 \, {\rm MeV}/{\rm fm}^2$, relevant for the surface of quark stars, and of the nuclear-quark transition $\Sigma_{\rm NQ}\sim 10 \, {\rm MeV}/{\rm fm}^2$, relevant for hybrid stars and for quark matter nucleation in supernovae and neutron star mergers.
Highlights
Identifying the chirally symmetric phase with quark matter—our model does not contain explicit quark degrees of freedom—we find maximal surface tensions of the vacuum-quark transition ΣVQ ∼ 15 MeV=fm2, relevant for the surface of quark stars, and of the nuclear-quark transition ΣNQ ∼ 10 MeV=fm2, relevant for hybrid stars and for quark matter nucleation in supernovae and neutron star mergers
We identify the parameter regimes for these possibilities and compute the surface tension for all three transitions
We have calculated the surface tension of dense matter within a nucleon-meson model, which accounts for realistic nuclear matter, but does not contain quark d.o.f
Summary
Possibly quark matter, play a crucial role in the astrophysics of neutron stars [1,2], from the structure of their cores to cataclysmic events associated with their formation in supernovae explosions and collision in neutron star mergers [3,4,5,6,7,8,9,10,11,12,13,14]. The density regimes where the two approaches are valid are far apart, such that at a possible first-order transition at least one of them, very likely both, cannot be trusted [29] Even if they happened to separately describe the low- and high-density phases reasonably well near the transition, this would be of little use for a rigorous calculation of the surface tension. Previous estimates of the surface tension were either performed in the framework of chiral models that lack the nuclear matter ingredient or employed two different models for nuclear and quark matter, which are glued together at the phase transition To fill this gap, we employ a nucleonmeson model [48,49,50,51] that contains realistic nuclear matter, in the sense that its parameters are matched to the known properties of nuclear matter at saturation density.
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