Interface tension and interface entropy in the2+1flavor Nambu–Jona-Lasinio model

Abstract

We study the QCD phases and their transitions in 2+1 flavour NJL model, with focus on the interface effects such as the interface tension, the interface entropy and critical bubble size in the coexistence region of the first order phase transitions. Our results show that, under the thin-wall approximation, interface contribution to total entropy density changes its discontinuity scale in the first order phase transition. However, the entropy density of dynamical chiral symmetry (DCS) phase is always greater than that of the dynamical chiral symmetry broken (DCSB) phase in both heating and hadronization processes. To address this entropy puzzle, the thin-wall approximation is evaluated in the present work. We find that the puzzle can be attributed to a drastic overestimate of the critical bubble size at low temperature in the hadronization process. With an improvement on the thin-wall approximation, the entropy puzzle is well solved with the total entropy density of the hadron-DCSB phase exceeding apparently that of the DCS-quark phase at low temperature.

Interface effect in QCD phase transitions via Dyson-Schwinger equation approach

“…Beyond the location of the CEP (µ χ,E q , T χ,E ) = (111, 128) MeV, the chiral phase transition of QCD becomes first order transition. Since the nucleation process describes the phase transition from a metastable phase to a stable phase, we find that the chiral phase transition takes place at different locations for different processes [81]. The DCSB to DCS phase transition takes place at higher chemical potential till the higher bound of the coexistence region, while for the opposite process, hadronization process accomplishes at low chemical potential till the lower bound of the coexistence region.…”

“…However, during the phase transition process, when the hadron bubble emerges in the DCS state, the interface tension will constrain the volume of the bubble to increase. Thusly, at this moment, the key to solve the entropy puzzle would be the inhomogeneity, i.e., the interface between the distinct phases of the system [81]. When the phase transition takes place, the two phases meet at an interface which gives additional interface entropy.…”

“…When the first order phase transition takes place, the two phases with different thermal properties, the dynamical chiral symmetry breaking (DCSB or Nambu) phase and the dynamical chiral symmetry preserved (DCS or Wigner) phase, meet at an interface. This interface effect, which is measured by the interface tension and related quantities such as the interface entropy and the critical size of the bubble [81,82], has been investigated by lattice QCD simulation [83] and many effective model calculations [74,[76][77][78][79][80][81][82][84][85][86][87][88][89][90]. On the other hand, it has been found for a long time that in the hadronization process there exists a so called entropy puzzle, that is, the entropy density of the quark-gluon phase is always larger than that of the hadron phase in both the hadronization (DCS to DCSB) process and the deconfinement (DCS restoration) process [81,86,[91][92][93], and thus, the hadronization process seems to be impossible according to the increasing entropy principle.…”

“…On the other hand, it has been found for a long time that in the hadronization process there exists a so called entropy puzzle, that is, the entropy density of the quark-gluon phase is always larger than that of the hadron phase in both the hadronization (DCS to DCSB) process and the deconfinement (DCS restoration) process [81,86,[91][92][93], and thus, the hadronization process seems to be impossible according to the increasing entropy principle. Effective model calculations have provided hints for that considering the interface entropy might solve this puzzle [81,86]. To make this solid, it is imperative to study the problem and solve the puzzle via sophisticated continuum QCD approach.…”

Hybrid Stars in the Framework of NJL Models

“…Some recent studies [14][15][16][17][18][19] predict the value of the surface tension around σ ∼ 5 − 30 MeV/fm 2 , while others [11][12][13]20, 21 obtain a value around σ ∼ 50 − 300 MeV/fm 2 . Comparing those works it can be seen that the results are strongly model dependent.…”