Speed of sound and quark confinement inside neutron stars

Nucleon Mass Sum Rule Violation in QCD and Confinement

In this paper we show that for a nucleon at rest if the quarks and/or antiquarks are in motion inside the nucleon producing chromo-magnetic field then the mass sum rule in QCD is violated when the confinement potential energy at large distance $r$ rises linearly with $r$ (or faster). Hence we find that the mass of the nucleon at rest is not equal to the mass-energy of all the quarks plus antiquarks plus gluons inside the nucleon if there exists chromo-magnetic field inside the nucleon and the confinement potential energy at large distance $r$ rises linearly with $r$ (or faster).

结合天体物理与 pQCD 约束对中子星内部声速非平凡特征的贝叶斯分析

Bayesian analysis of nontrivial features in the speed of sound inside neutron stars in light of astrophysical and pQCD constraints

本文利用改进高斯过程建模含隆起、弯折与平台的中子星 EoS，并结合 X 射线、引力波及 pQCD 约束进行贝叶斯分析，证明这些声速特征仍可行且有助于识别约 2 n_sat 处的相结构。

Hot Quark Matter with Neutrino Confinement in the Framework of the Local Nambu--Jona-Lasinio SU(3) Model

The thermodynamic characteristics of hot $β$-equilibrium electrically neutral three-flavor quark matter at neutrino confinement are investigated. For the thermodynamic description of such a quark-lepton system, the local SU (3) Nambu--Jona-Lasinio (NJL) model is used, in which also takes into account the 't Hooft interaction, leading to the quark flavor mixing effect. The energy density $\varepsilon$ and pressure $P$ of quark matter are numerically determined for different values of the baryon number density in the range $n_B\in[0.02÷1.8]$ fm$^{-3}$ and temperatures in the range $T\in[0÷100]$ …

Constraining the speed of sound inside neutron stars with chiral effective field theory interactions and observations

The dense matter equation of state (EOS) determines neutron star (NS) structure but can be calculated reliably only up to one to two times the nuclear saturation density, using accurate many-body methods that employ nuclear interactions from chiral effective field theory constrained by scattering data. In this work, we use physically motivated ansatzes for the speed of sound $c_S$ at high density to extend microscopic calculations of neutron-rich matter to the highest densities encountered in stable NS cores. We show how existing and expected astrophysical constraints on NS masses and radii fr…

中子星内部声速的非平凡特征

Nontrivial features in the speed of sound inside neutron stars

本研究提出基于高斯过程生成含非平凡特征的中子星状态方程集合的方法，经贝叶斯分析验证其符合现有观测约束，还发现声速全局最大值的存在与当前约束相容但非必需。

Determination of shear forces inside the proton

We report on the first determination of the shear forces quarks inside the proton from experimental data on deeply virtual Compton scattering. The maximum shear force of approximately 40 MeV/fm occurs near 0.6 fm from the proton center, indicating where confinement forces may be strongest. On the macroscopic scale of the earth surface, this force corresponds to the weight of a mass of about 650 kg. The shear forces in the proton reverse direction at r = 0.45 fm from the center.