arXiv subjects

Zhi-Jun Ma

Publications and source records attributed to Zhi-Jun Ma.

3 recordsLinked to original sources

arXiv2026

Lattice-data-driven specific heat and isentropic bulk modulus of SU(3) gluon matter at finite temperature

We investigate the specific heat and isentropic bulk modulus of finite-temperature pure SU(3) gauge matter within a lattice-data-driven phenomenological framework. The equation of state is formulated in terms of a temperature-dependent effective gluon mass constrained { by lattice QCD pressure data as input, allowing the pressure}, trace anomaly, gluon number density, energy per thermally active gluonic mode, and derivative-sensitive response functions to be derived in a thermodynamically consistent manner. The resulting pressure and trace anomaly reproduce the characteristic lattice behavior across the deconfinement region, while the effective gluonic degrees of freedom increase rapidly above $T_c$. The normalized specific heat $C_V/T^3$ develops a pronounced enhancement in the vicinity of $T_c$, reflecting the rapid temperature variation of the energy density across the deconfinement region. The isentropic bulk modulus $K_S/T^4$ also rises sharply across the transition region, indicating a substantial stiffening of the equation of state. At high temperatures, both response functions gradually approach values close to their massless conformal Stefan--Boltzmann reference values, with $\left(C_V/T^3\right)_{\rm SB}=32π^2/15\simeq 21.06$ and $\left(K_S/T^4\right)_{\rm SB}=32π^2/135\simeq 2.34$. These findings indicate that the specific heat and isentropic bulk modulus provide complementary constraints on the temperature evolution of nonconformal dynamics in pure SU(3) gauge matter.

hep-ph↗

arXiv2025

Probing the nonstrange quark star equation of state with compact stars and gravitational waves

A recent study shows that incorporating a new term into the thermodynamic potential density, as required by the thermodynamic consistency criterion, can effectively resolve the thermodynamic inconsistency problems of the conventional perturbative QCD model. This additional term plays a crucial role in resolving inconsistencies at relatively low densities and becomes negligible at extremely high densities. Within this revised perturbative QCD model, we find that if we require only that the energy per baryon of up-down ($ud$) quark matter exceeds 930 MeV so as not to contradict the standard nuclear physics, the maximum mass of an $ud$ quark star allowed by the revised perturbative QCD model can reach up to 2.17 $M_{\odot}$. From this perspective, the observed 2.14 $M_{\odot}$ pulsar PSR J0740+6620 may be an $ud$ quark star. However, if we further impose the constraint that the tidal deformability of a 1.4 $M_{\odot}$ $ud$ quark star must be consistent with the GW170817 event, the maximum mass allowed by the revised perturbative QCD model would decrease to no more than 2.08 $M_{\odot}$. Consequently, our results suggest that the compact object with a mass of 2.50-2.67 $M_{\odot}$, as observed in the GW190814 event, cannot be an $ud$ quark star, according to the revised perturbative QCD model.

hep-ph↗

arXiv2023

Cold quark matter in a quasiparticle model: thermodynamic consistency and stellar properties

The strong coupling in the effective quark mass was usually taken as a constant in a quasiparticle model while it is, in fact, running with an energy scale. With a running coupling, however, the thermodynamic inconsistency problem appears in the conventional treatment. We show that the renormalization subtraction point should be taken as a function of the summation of the biquadratic chemical potentials if the quark's current masses vanish, in order to ensure full thermodynamic consistency. Taking the simplest form, we study the properties of up-down ($ud$) quark matter, and confirm that the revised quasiparticle model fulfills the quantitative criteria for thermodynamic consistency. Moreover, we find that the maximum mass of an $ud$ quark star can be larger than two times the solar mass, reaching up to $2.31M_{\odot}$, for reasonable model parameters. However, to further satisfy the upper limit of tidal deformability $\tildeΛ_{1.4}\leq 580$ observed in the event GW170817, the maximum mass of an $ud$ quark star can only be as large as $2.08M_{\odot}$, namely $M_{\text{max}}\lesssim2.08M_{\odot}$. In other words, our results indicate that the measured tidal deformability for event GW170817 places an upper bound on the maximum mass of $ud$ quark stars, but which does not rule out the possibility of the existence of quark stars composed of $ud$ quark matter, with a mass of about two times the solar mass.

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