A generic feature of scalar extensions of general relativity is the coupling of the scalar degrees of freedom to the trace $T$ of the energy-momentum tensor of matter fields. Interesting phenomenology arises when the trace becomes positive---when pressure exceeds one third of the energy density---a condition that may be satisfied in the core of neutron stars. In this work, we study how the positiveness of the trace of the energy-momentum tensor correlates with macroscopic properties of neutron stars. We first show that the compactness for which $T=0$ at the stellar center is approximately equation-of-state independent, and given by $C = 0.262_{-0.017}^{+0.011}$ (90% confidence interval). Next, we exploit Bayesian inference to derive a probability distribution function for the value of $T$ at the stellar center given a putative measurement of the compactness of a neutron star. This investigation is a necessary step in order to use present and future observations of neutron star properties to constrain scalar-tensor theories based on effects that depend on the sign of $T$.
General gravitational properties of neutron stars: curvature invariants, binding energy, and trace anomaly
Goethe Universität（法兰克福歌德大学）；Instituto de Astronomía, Universidad Nacional Autónoma de México（墨西哥国立自治大学天文研究所）；School of Mathematics, Trinity College（都柏林三一学院数学学院）；Frankfurt Institute for Advanced Studies（法兰克福高等研究院）
Rotating neutron stars within the macroscopic effective-surface approximation
Institute for Nuclear Research, Kyiv（基辅核物理研究所）；Southern Center for Nuclear-Science Theory (SCNT), Institute of Modern Physics, Chinese Academy of Sciences, Huizhou（中国科学院近代物理研究所惠州南方核科学理论中心）；Cyclotron Institute, Texas A&M University, College Station, Texas（德克萨斯农工大学回旋加速器研究所）；School of Physics and Information Technology, Shaanxi Normal University, Xi’an（陕西师范大学物理与信息工程学院）
Macroscopic backreaction of the trace anomaly on classical vacuum backgrounds
Instituto de Astrofísica de Andalucía (IAA-CSIC)（安达卢西亚天体物理研究所）；Center of Gravity, Niels Bohr Institute（引力中心，尼尔斯·玻尔研究所）；Institut für Theoretische Physik（理论物理研究所）；Center for Gravitational Physics and Quantum Information, Yukawa Institute for Theoretical Physics, Kyoto University（京都大学汤川理论物理研究所引力物理与量子信息研究中心）；Research Center for the Early Universe (RESCEU), Graduate School of Science, The University of Tokyo（东京大学理学研究系宇宙早期研究センター(RESCEU)）；Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo Institutes for Advanced Study, The University of Tokyo（东京大学前沿研究机构 Kavli宇宙物理数学研究所(WPI)）
Trace Anomaly and Effective Topological Sources in Neutron Stars
Università degli Studi della Campania “Luigi Vanvitelli”（坎帕尼亚路易吉范维特利大学）；Istituto Nazionale di Fisica Nucleare, Sezione di Napoli（意大利国家核物理研究所，那不勒斯分部）；Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati（意大利国家核物理研究所，弗拉斯卡蒂国家实验室）
