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arXiv 1903.09121astro-ph.HEhep-phnucl-th
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大质量中子星中存在夸克物质核的证据

Evidence for quark-matter cores in massive neutron stars

Eemeli Annala, Tyler Gorda, Aleksi Kurkela, Joonas Nättilä, Aleksi Vuorinen

摘要:

控制强核力的量子色动力学理论预言,在足够高的能量密度下,强子核物质会经历一个去禁闭的过渡,变成一个新的夸克和胶子相。虽然这在超相对论重离子碰撞中已经被观察到,但目前中子星内部是否存在夸克物质还是一个悬而未决的问题。通过结合天体物理观测和理论从头计算,在一个独立的模型的方式,我们发现,在中子星的质量对应于1.4太阳质量的核心的物质的推断性质是兼容的核模型计算。然而,在最大质量,稳定的中子星内部的物质表现出退禁闭相的特征,我们解释为夸克物质核心存在的证据。对于可靠观测到的质量约为两个太阳质量的最重中子星,夸克物质的存在被发现与强相互作用物质中的声速c_s的行为有关。如果没有强烈地违反共形边界(c_s)^2 < 1/3,那么大质量中子星被预言具有相当大的夸克物质核心。这一发现对中子星的现象学有重要的意义,并影响至少有一个足够大质量的参与者的中子星合并的动力学。

英文摘要:

The theory governing the strong nuclear force, Quantum Chromodynamics, predicts that at sufficiently high energy densities hadronic nuclear matter undergoes a deconfinement transition to a new phase of quarks and gluons. Although this has been observed in ultrarelativistic heavy-ion collisions, it is currently an open question whether quark matter exists inside neutron stars. By combining astrophysical observations and theoretical ab-initio calculations in a model-independent way, we find that the inferred properties of matter in the cores of neutron stars with mass corresponding to 1.4 solar masses are compatible with nuclear model calculations. However, the matter in the interior of maximally massive, stable neutron stars exhibits characteristics of the deconfined phase, which we interpret as evidence for the presence of quark-matter cores. For the heaviest reliably observed neutron stars with masses of about two solar masses, the presence of quark matter is found to be linked to the behaviour of the speed of sound c_s in strongly interacting matter. If the conformal bound (c_s)^2 < 1/3 is not strongly violated, massive neutron stars are predicted to have sizable quark-matter cores. This finding has important implications for the phenomenology of neutron stars, and affects the dynamics of neutron star mergers with at least one sufficiently massive participant.

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