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arXiv 1405.4547gr-qcastro-ph.HEhep-th
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I-Love-Q,Sponsor:标量张量理论中的慢转中子星

I-Love-Q, Spontaneously: Slowly Rotating Neutron Stars in Scalar-Tensor Theories

Paolo Pani, Emanuele Berti

摘要:

我们通过将经典的Hartle-Thorne形式主义扩展到一般的标量张量引力理论,构建了缓慢旋转的理想流体中子星模型。在无量纲角动量的二阶下,我们计算了质量M,半径R,标量电荷q,转动惯量I和自旋诱导四极矩Q,以及潮汐和旋转Love数。我们的形式主义适用于一般的标量张量理论,但我们特别关注的理论,允许自发标量化。最近发现,转动惯量、四极矩和勒夫数通过近似万有(即,状态方程独立)“I-Love-Q”关系。我们发现,类似的关系也适用于自发标度化的恒星。更有趣的是,标量张量理论中的I-Love-Q关系与广义相对论的I-Love-Q关系在不到百分之几的范围内重合,即使是对于当前脉冲双星约束所允许的最大耦合的自发标量化恒星。这意味着这些参数的天体物理测量不能用来区分广义相对论和标量张量理论,即使自发标量化发生在自然界中。由于f(R)理论与标量张量理论之间的等价性,本文所建立的理论框架可以用来构造f(R)引力下的旋转致密恒星模型。我们的慢旋转膨胀也可以作为一个基准的快速旋转的中子星的一般标量张量理论的数值计算。

英文摘要:

We construct models of slowly rotating, perfect-fluid neutron stars by extending the classical Hartle-Thorne formalism to generic scalar-tensor theories of gravity. Working at second order in the dimensionless angular momentum, we compute the mass M, radius R, scalar charge q, moment of inertia I and spin-induced quadrupole moment Q, as well as the tidal and rotational Love numbers. Our formalism applies to generic scalar-tensor theories, but we focus in particular on theories that allow for spontaneous scalarization. It was recently discovered that the moment of inertia, quadrupole moment and Love numbers are connected by approximately universal (i.e., equation-of-state independent) "I-Love-Q" relations. We find that similar relations hold also for spontaneously scalarized stars. More interestingly, the I-Love-Q relations in scalar-tensor theories coincide with the general relativistic ones within less than a few percent, even for spontaneously scalarized stars with the largest couplings allowed by current binary-pulsar constraints. This implies that astrophysical measurements of these parameters cannot be used to discriminate between general relativity and scalar-tensor theories, even if spontaneous scalarization occurs in nature. Because of the well known equivalence between f(R) theories and scalar-tensor theories, the theoretical framework developed in this paper can be used to construct rotating compact stellar models in f(R) gravity. Our slow-rotation expansion can also be used as a benchmark for numerical calculations of rapidly spinning neutron stars in generic scalar-tensor theories.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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