Baryons and QCD equation of state at large densities

在对记录为GW170817的双中子星合并事件的引力波进行观测和分析后，中子星的物理学受到了巨大的国际关注。像NICER/ISS这样的专门实验有望在近期和中期提供有趣的额外信息。中子星物理学的一个中心对象是强相互作用理论（QCD）描述的强相互作用物质的状态方程（EOS）。从理论的角度来看，在QCD物质的中间密度的重要区域，EOS并不为人所熟知。虽然有效的手性场理论和微扰方法在低密度和（非常）大密度区域提供了可靠的结果，但在中间区域的模型结果受到人工和系统误差的阻碍。在这个项目中，我们提出了一个高质量的状态方程（EOS）的QCD物质在小，中，大密度在一个相同的方法基于QCD。我们的主要技术是通过Dyson-Schwinger和Bethe-Salpeter方程来实现QCD的功能方法，该方法已经成功地应用于QCD相图的物理，介质对强子的物理影响以及重子光谱的物理。基于这些专业知识，我们计划特别关注中密度区域，其中可能包括从强子到夸克物质相的转变，其特征是双夸克凝聚。热力学在这个区域的关键自由度是费米子，即重子和夸克。在强子相，我们计划确定重子的质量和波函数，并将它们的影响纳入EOS。我们将研究它们在潜在一阶相变的共存区域和（彩色）超导区域的命运，在那里夸克效应预计将主导EOS。在我们的框架中正确的高密度微扰极限已经在以前的工作中得到了证明。如果成功，我们将能够在定性和定量上对先前的EOS测定结果进行重大改进，并对中子星物理学和重离子碰撞物理学这两个及时的研究领域产生潜在的重大影响。

The physics of neutron stars has received tremendous international attention after the observation and analysis of gravitational waves from a binary-neutron-star merger event recorded as GW170817. Dedicated experiments such as NICER/ISS promise to provide interesting additional information in the near and middle future. A central object of the physics of neutron stars is the equation of state (EOS) of strongly interacting matter described by the theory of strong interactions, QCD. From a theory perspective, the EOS is not well known in the important region of intermediate densities of QCD matter. Whereas effective chiral field theories and perturbative approaches provide solid results in the low and (very) large density region, model results in the intermediate region are hampered by artefacts and systematic errors. In this project we propose to provide a high-quality equation of state (EOS) for QCD matter at small, intermediate and large densities in one and the same approach based on QCD. Our technical workhorse is a functional approach to QCD via Dyson-Schwinger and Bethe-Salpeter equations that has been successfully applied already to the physics of the QCD phase diagram, the physics of medium effects on hadrons and the physics of baryon spectra by my group. Based on this expertise we plan to focus particularly on the intermediate density region which may include the transition from a hadronic to a quark matter phase characterized by diquark condensation. The key degrees of freedom for thermodynamics in this region are fermions, i.e., baryons and quarks. In the hadronic phase we plan to determine the masses and wave functions of baryons and incorporate their effects into the EOS. We will study their fate in the coexistence region of a potential first order phase transition and in the (colour) superconducting region beyond, where quark effects are expected to dominate the EOS. The correct high density perturbative limit in our framework has been demonstrated already in previous works. If successful, we will be able to provide significant qualitative and quantitative improvements of previous determinations of the EOS with potential large impact on two timely research fields, the physics of neutron stars and the physics of heavy ion collisions.