论文标题
Rastall重力对PULSAR PSR J0740+6620的质量，半径和音速的影响
Impact of Rastall gravity on mass, radius and sound speed of the pulsar PSR J0740+6620
论文作者
论文摘要
毫秒脉冲星是测试可能的物质几何耦合及其物理含义的理想实验室，鉴于最近的中子星内部组成探索器（较好）观测值。我们将重力的rastall场方程（在非微小耦合）上应用于Krori-Barua内部时空，而物质源则被认为是各向异性流体。我们表明，恒星内的所有物理数量都可以用rastall，$ε$和紧凑型表示，$ c = 2gm/rc^2 $，参数。使用PULSAR PSR PSR J0740+6620的质量和半径上的X射线和X射线多MIRROR X射线观测约束，我们确定Rastall参数最多为$ε= 0.041 $在正范围内。获得的解决方案提供了一个稳定的紧凑对象；此外，平方的音速不会违反猜想的声速$ c_s^2 \ leq c^2/3 $，与一般相对论治疗不同。我们注意到没有假定国家方程式；然而，该模型与带袋常数的线性图案非常吻合。通常，对于$ε> 0 $，该理论与同一质量的一般相对性相比，预测尺寸稍大。由于物质几何耦合，在流体动力平衡方程中，这已被解释为一种额外的力，这有助于部分降低重力效应。因此，我们计算出强能量条件允许的最大紧凑性为$ c = 0.735 $，$ \ sim 2 \％$比一般相对性预测高。此外，对于在饱和度处的表面密度，核密度$ρ_ {\ text {nuc}} = 2.7 \ times 10^{14} $ g/cm $^3 $我们估计最大质量$ m = 4 m_ \ odot $ radius $ radius $ r = 16 $ r = 16 $ km。
Millisecond pulsars are perfect laboratories to test possible matter-geometry coupling and its physical implications in light of recent Neutron Star Interior Composition Explorer (NICER) observations. We apply Rastall field equations of gravity, where matter and geometry are nonminimally coupled, to Krori-Barua interior spacetime whereas the matter source is assumed to be anisotropic fluid. We show that all physical quantities inside the star can be expressed in terms of Rastall, $ε$, and compactness, $C=2GM/Rc^2$, parameters. Using NICER and X-ray Multi-Mirror X-ray observational constraints on the mass and radius of the pulsar PSR J0740+6620 we determine Rastall parameter to be at most $ε=0.041$ in the positive range. The obtained solution provides a stable compact object; in addition the squared sound speed does not violate the conjectured sound speed $c_s^2\leq c^2/3$ unlike the general relativistic treatment. We note that no equations of state are assumed; the model however fits well with linear patterns with bag constants. In general, for $ε>0$, the theory predicts a slightly larger size star in comparison to general relativity for the same mass. This has been explained as an additional force, due to matter-geometry coupling, in the hydrodynamic equilibrium equation, which contributes to partially diminish the gravitational force effect. Consequently, we calculate the maximal compactness as allowed by the strong energy condition to be $C = 0.735$ which is $\sim 2\%$ higher than general relativity prediction. Moreover, for the surface density at saturation nuclear density $ρ_{\text{nuc}} = 2.7\times 10^{14}$ g/cm$^3$ we estimate the maximum mass $M=4 M_\odot$ at radius $R=16$ km.
