arXiv 1807.089512018-07-24hep-ph

玻色-爱因斯坦凝聚与π介子星

Bose-Einstein condensation and pion stars

Jens O. Andersen, Patrick Kneschke

备注：: 11 pages and 5 figures

摘要：

由玻色-爱因斯坦凝聚态带电π介子组成的π星是最近提出的一类新的致密星。在$1/N$展开式中，我们用两粒子不可约有效作用量来描述带电和中性π介子以及σ粒子。正确调整拉格朗日量中的参数，荷电π介子的玻色-爱因斯坦凝聚的起始点正好在$μ_I=m_π$，其中$μ_I$是同位旋化学势。我们计算的压力，能量密度，和状态方程，这是作为输入的托尔曼-奥本海默-Volkov方程。解这些方程，我们得到了π星的质量半径关系。通过增加自由相对论轻子气体对压力和能量密度的贡献，确保了整体电荷中性。我们比较我们的结果与最近的晶格模拟，发现很好的协议。π星的质量大约为200个太阳质量，而相应的半径为$10^5$ km。

英文摘要：

Pion stars consisting of Bose-Einstein condensed charged pions have recently been proposed as a new class of compact stars. We use the two-particle irreducible effective action to leading order in the $1/N$-expansion to describe charged and neutrals pions as well as the sigma particle. Tuning the parameters in the Lagrangian correctly, the onset of Bose-Einstein condesation of charged pions is exactly at $μ_I=m_π$, where $μ_I$ is the isospin chemical potential. We calculate the pressure, energy density, and equation of state, which are used as input to the Tolman-Oppenheimer-Volkov equations. Solving these equations, we obtain the mass radius-relation for pion stars. Global electric charge neutrality is ensured by adding the contribution to the pressure and energy density from a gas of free relativistic leptons. We compare our results with those of recent lattice simulations and find good agreement. The masses of the pion stars are up to approximately 200 solar masses while the corresponding radii are of the order of $10^5$ km.

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