压缩重子物质：从原子核到脉冲星

尽管物质世界以不熟悉的暗物质、暗能量为主，但自然界的精彩却要归功于相对少量的那些重子物质．日常生活中原子核之间Coulomb排斥有效地阻止它们通过挤压物质而聚合起来，然而天体极端环境时常出人意料：大质量恒星演化至晚期时，其核心引力如此之强以至于其他任何力（当然包括Coulomb排斥）都难以媲美——压缩重子物质就这样在超新星爆发过程中诞生，并表现为观测到的脉冲星．对这类压缩重子物质的研究将不仅加深对强作用基本性质的认识，而且有助于检验引力理论、探测低频引力波、建立精确的时间标准和导航体系，还是我国在建或拟建大型天文望远镜的核心课题．历史上Landau曾推测恒星核心存在巨大的原子核（后来发展成为“中子星”模型），我们经过研究后却认为脉冲星其实是由夸克集团而构成的凝聚体．夸克集团作为超新星爆发形成压缩重子物质的基本单元这一想法十年来并未被观测排除，而且我们还期待未来功能更强大的观测设备检验它．

Compressed baryonic matter： from nuclei to pulsars

Our world is wonderful because of the negligible baryonic part although unknown dark matter and dark energy dominate the Universe. Those nuclei in the daily life are forbidden to fuse by compression due to the Coulomb repulse, nevertheless, it is usually unexpected in extraterrestrial extreme-environments： the gravity in a core of massive evolved star is so strong that all the other forces （including the Coulomb one） could be neglected. Compressed baryonic matter is then produced after supernova, manifesting itself as pulsar-like stars observed. The study of this compressed baryonic matter can not only be meaningful in fundamental physics （e.g., the elementary color interaction at low-energy scale, testing gravity theories, detecting nano-Hertz background gravitational waves）, but has also profound implications in engineering applications （including time standard and navigation）, and additionally, is focused by Chinese advanced telescopes, either terrestrial or in space. Historically, in 1930s, L. Landau speculated that dense matter at supra-nuclear density in stellar cores could be considered as gigantic nuclei （the prototype of standard model of neutron star）, however, we address that the residual compact object of supernova could be of condensed matter of quark clusters. The idea that pulsars are quark-cluster stars was not ruled out during the last decade, and we are expecting to test further by future powerful facilities.