Twin stars: probe of phase transition from hadronic to quark matter
T. Deloudis, P. S. Koliogiannis, Ch. C. Moustakidis
备注：
v1: 4 pages, 2 figures. v2: references have been added; to be published in the proceedings of 6th workshop of the Hellenic Institute of Nuclear Physics(HINP)
In agreement with the gravitational-wave events which are constantly increasing, new aspects of the internal structure of compact stars have come to light. A scenario in which a first order transition takes place inside these stars is of particular interest as it can lead, under conditions, to a third gravitationally stable branch (besides white dwarfs and neutron stars). This is known as the twin star scenario. The new branch yields stars with the same mass as normal compact stars but quite different radii. In the current work, we focus on hybrid stars undergone a hadron to quark phase transition near their core and how this new stable configuration arises. Emphasis is to be given especially in the aspects of the phase transition and its parameterization in two different ways, namely with Maxwell construction and with Gibbs construction. Qualitative findings of mass-radius relations of these stars will also be presented.
Twins in the Shadow: Phase Transitions in Proto-Neutron Stars
Hamburger Sternwarte, University of Hamburg（汉堡天文台，汉堡大学）；The Oskar Klein Centre, Department of Astronomy, AlbaNova, Stockholm University（奥斯卡·克莱因中心，天文学系，阿尔巴诺瓦，斯德哥尔摩大学）
Twin stars and the stiffness of the nuclear equation of state: ruling out strong phase transitions below $1.7n_0$ with the new NICER radius measurements
High-mass twins & resolution of the reconfinement, masquerade and hyperon puzzles of compact star interiors
我们的目标是有助于解决与致密星致密核结构（CS）有关的三个基本难题：（i）超子难题：如何协调$2\,$ M $_\odot$的脉冲星质量与超子软化状态方程（EoS）;（ii）伪装问题：现代EOS冷，高密度强子和夸克物质几乎是相同的;（iii）的refinement难题：怎么办时，解除禁闭过渡后的强子EOS再次成为有利的？我们表明，考虑到重子的复合性（排除体积和/或夸克泡利阻塞）的强子侧和夸克物质侧的限制和硬化效应的结果在早期的相变到夸克物质，在高密度，消除了所有三个目前的CS内部的困惑。此外，在这类新的EoS的混合CS下降的一个有趣的情况下，一个强的一阶相变，导致可观察到的高质量的双星现象，天体物理观测的一个关键端点的QCD相图。
Bayesian Inference of Dense-Matter Equations of State from Small-Radius Compact Stars with Twin-Star Scenarios
School of Physics, Nankai University（南开大学物理学院）；Shenzhen Research Institute of Nankai University（南开大学深圳研究院）；Department of Physics, Faculty of Science, Tianjin University（天津大学理学院物理系）
本文通过贝叶斯方法研究致密物质方程 of state，探讨小半径致密星体是否能被双星情景所容纳，通过约束参数发现相变特征及对潮汐变形性的影响。
Indian Institute of Science Education and Research（印度科学教育研究所）；Goethe Universität（法兰克福歌德大学）；School of Mathematics, Trinity College（都柏林圣三一学院数学系）；Frankfurt Institute for Advanced Studies（法兰克福高等研究院）
A new quark-hadron hybrid equation of state for astrophysics - I. High-mass twin compact stars
目的：提出了一个新的微观强子-夸克混合状态方程模型，并由此构造了紧凑的混合星构型。它们由夸克核和强子壳层组成，在它们的界面处有一级相变。由此产生的质量-半径关系符合最新的天体物理学约束。研究方法：夸克物质的描述是基于量子色动力学（QCD）激发的手征方法与高阶夸克相互作用的狄拉克标量和矢量耦合通道。对于强子物质，我们选择一个相对论性的平均场状态方程与密度依赖的耦合。由于核子是在准粒子框架下处理的，考虑到核子的有限尺寸，对超饱和密度下的核物质状态方程进行了排除体积修正。结果如下：这些新的方面，在强子阶段和高阶排斥相互作用的强子阶段，导致一个强大的一阶相变与大潜热，即能量密度跳跃在相变，这满足了一个标准的不连续的第三家族分支的致密恒星的质量-半径关系。这些双星的质量很高（$\sim$ 2 M $_\odot$），与目前观测到的高质量双星有关。结论：这一分析提供了一种独特的可能性，通过对致密星的半径观测来探测零温和大化学势下的QCD相图，甚至支持QCD相图中临界点的存在。
Twin stars as probes of the nuclear equation of state: effects of rotation through the PSR J0952-0607 pulsar and constraints via the tidal deformability from the GW170817 event
