Interface effects of strange quark matter

Abstract

The interface effects play important roles for the properties of strange quark matter (SQM) and the related physical processes. We show several examples on the implications of interface effects for both stable and unstable SQM. Based on an equivparticle model and adopting mean-field approximation (MFA), the surface tension and curvature term of SQM can be obtained, which are increasing monotonically with the density of SQM at zero external pressure. For a parameter set constrained according to the 2M ⊙ strange star, we find the surface tension is ∼2.4 MeV/fm 2 , while it is larger for other cases.

Systematic study on the quark-hadron mixed phase in compact stars

“…Note that at μ B ≈ 1400 MeV, for few cases, the perturbation model predicts smaller baryon number density of quark matter than that of hadronic matter, which causes fluctuations if the surface tension is estimated with Σ ¼ 14.3Δn þ 1.3. At larger μ B , the relation 0.3Σ MRE ≈ 14.3Δn þ 1.3 can be fulfilled approximately, which coincides with the predictions of equivparticle model [62,63]. With the surface tension values indicated in Fig.…”

“…With the properties of both hadronic matter and quark matter fixed, the structures of quark-hadron mixed phase are obtained assuming a continuous dimensionality as proposed by Ravenhall et al [57]. The energy contribution due to the quark-hadron interface is treated with a surface tension Σ, where we have taken constant values for Σ as well as those estimated by the multiple reflection expansion method [58][59][60][61] and equivparticle model including both linear confinement and leading-order perturbative interactions [62,63]. The critical surface tension Σ c that accounts for the energy reduction due to the relocation of charged particles is estimated for various combinations of quark and hadronic EOSs.…”

“…(13). A smoothly varying quark density is then obtained on the interface, where the surface tension was found to be connected with the density of quark matter by Σ ≈ 14.3n Q þ 1.3 (in MeV=fm 2 ) [63]. Meanwhile, it was shown that the surface tension predicted by the MRE method coincides with equivparticle model if we introduce a dampening factor, i.e., Σ ¼ 0.3…”

“…The surface tension predicted by the MRE method is then obtained with Σ ¼ Σ MRE ¼ P i¼u;d;s Σ MRE i . Nevertheless, the MRE method tends to overestimate the surface tension by twice the value obtained with equivparticle model [62,63]. This is mainly due to the different confinement potential adopted in those models, where the bag mechanism of the MRE method introduces an infinite wall that results in a sharp density discontinuity.…”

“…Note that the surface tension obtained by the equivparticle model [62,63] was for the quark-vacuum interface. The contributions from the hadron phase can be roughly included by replacing the density of quark matter n Q by the density difference Δn ≡ jn Q − n H j between the two phases.…”