Neutron stars with a generalized Proca hair and spontaneous vectorization
Neutron stars with a generalized Proca hair and spontaneous vectorization
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DOI：
10.1103/physrevd.102.024067
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发表时间：
2020-01
影响因子：
5
通讯作者：
R. Kase;Masato Minamitsuji;S. Tsujikawa
中科院分区：
文献类型：
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作者：
R. Kase;Masato Minamitsuji;S. Tsujikawa
在一类广义普罗卡理论中，我们研究了矢量场 $A_\mu$ 的非零时间分量向空间无穷大接近 0 的中子星解的存在性，因为它们可能是广义相对论中 $A_{\mu}=0$ 中子星解的快子不稳定性的端点。这种现象称为自发矢量化，类似于标量张量理论中与曲率或物质具有非最小耦合的自发标量化。对于非最小耦合 $\beta X R$，其中 $\beta$ 是耦合常数，$X=-A_{\mu}A^{\mu}/2$，我们证明无论核物质状态方程的选择如何，都存在 0 节点和 1 节点矢量场解。 0 节点解仅在 $\beta=-{\cal O}(0.1)$ 时出现，可能是由一些非线性效应（例如所选的初始条件）引起的。 $\beta=-{\cal O}(1)$ 存在 1 节点解，它突然出现在恒星的临界中心密度之上，并随着中心密度的增加而接近广义相对论分支。我们计算了一些现实状态方程的中子星质量 $M$ 和半径 $r_s$，并表明 0 节点和 1 节点解的 $M$-$r_s$ 关系与标量张量理论中的标量解表现出显着差异。最后，我们讨论快子不稳定性的可能终点。
In a class of generalized Proca theories, we study the existence of neutron star solutions with a nonvanishing temporal component of the vector field $A_\mu$ approaching 0 toward spatial infinity, as they may be the endpoints of tachyonic instabilities of neutron star solutions in general relativity with $A_{\mu}=0$. Such a phenomenon is called spontaneous vectorization, which is analogous to spontaneous scalarization in scalar-tensor theories with nonminimal couplings to the curvature or matter. For the nonminimal coupling $\beta X R$, where $\beta$ is a coupling constant and $X=-A_{\mu}A^{\mu}/2$, we show that there exist both 0-node and 1-node vector-field solutions, irrespective of the choice of the equations of state of nuclear matter. The 0-node solution, which is present only for $\beta=-{\cal O}(0.1)$, may be induced by some nonlinear effects such as the selected choice of initial conditions. The 1-node solution exists for $\beta=-{\cal O}(1)$, which suddenly emerges above a critical central density of star and approaches the general relativistic branch with the increasing central density. We compute the mass $M$ and radius $r_s$ of neutron stars for some realistic equations of state and show that the $M$-$r_s$ relations of 0-node and 1-node solutions exhibit notable difference from those of scalarized solutions in scalar-tensor theories. Finally, we discuss the possible endpoints of tachyonic instabilities.