Neutron stars in f(R) gravity and scalar-tensor theories
Neutron stars in f(R) gravity and scalar-tensor theories
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DOI：
10.1088/1475-7516/2019/09/054
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发表时间：
2019-06
影响因子：
6.4
通讯作者：
R. Kase;S. Tsujikawa
中科院分区：
文献类型：
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作者：
R. Kase;S. Tsujikawa
在f（R）引力和Brans-Dicke理论中，我们研究了球对称静态背景下中子星的结构，给出了两种状态方程：SLy和FPS。在无质量BD理论中，与广义相对论相比，标量耦合Q的存在会改变星星的半径，而中子星的最大允许质量几乎不会被SLy和FPS状态方程修改。在Brans-Dicke理论中，质量势V（λ）=m2 λ 2/2，其中m2是一个正的常数，由于在星星外存在一个指数增长模，我们证明了实现具有稳定场分布的中子星星解的困难性.与具有R ~ 2项的f（R）引力一样，这一性质与星星表面场的附加边界条件的要求有关。对于自耦合势V（λ）=λ <$4/4，这个问题可以通过二阶导数V，λ <$2 =3λ <$2在空间无穷远处趋近于0的事实来解决。在这种情况下，我们用数值方法证明了SLy和FPS状态方程的中子星星解的存在性，并讨论了与广义相对论相比，质量-半径关系是如何修改的。
In f(R) gravity and Brans-Dicke theory with scalar potentials, we study the structure of neutron stars on a spherically symmetric and static background for two equations of state: SLy and FPS . In massless BD theory, the presence of a scalar coupling Q with matter works to change the star radius in comparison to General Relativity, while the maximum allowed mass of neutron stars is hardly modified for both SLy and FPS equations of state. In Brans-Dicke theory with the massive potential V(ϕ)=m2 ϕ2/2, where m2 is a positive constant, we show the difficulty of realizing neutron star solutions with a stable field profile due to the existence of an exponentially growing mode outside the star. As in f(R) gravity with the R2 term, this property is related to the requirement of extra boundary conditions of the field at the surface of star. For the self-coupling potential V(ϕ)=λ ϕ4/4, this problem can be circumvented by the fact that the second derivative V,ϕ ϕ=3λϕ2 approaches 0 at spatial infinity. In this case, we numerically show the existence of neutron star solutions for both SLy and FPS equations of state and discuss how the mass-radius relation is modified as compared to General Relativity.