标题： 类星体引力作为暗物质的替代方案 显示英文标题

标题： Chameleon Gravity as an Alternative to Dark Matter

摘要： 通过研究星系尺度上的类变色龙引力，我们探讨了类变色龙暗物质的影响。 为了完成这项任务，我们考虑在静态球对称时空中星系晕区域的类变色龙标量场的动力学，这些时空与经典广义相对论略有不同，但在此区域具有相似的对称性。 因此，我们证明了它作为暗物质的能力。 事实上，通过获得该区域切向速度的表达式，我们将这种方法应用于解释平坦星系旋转曲线的问题。 我们得到的结果是，与类变色龙标量场相关的质量随星系半径线性变化，因此该区域的切向速度是恒定的，这与观测数据一致，而无需引入神秘的暗物质。 因此，我们表明所提出的类变色龙引力具有明确的牛顿极限，并能够描述平坦星系旋转曲线区域的时空几何，并且与$ \Lambda CDM $模型的NFW轮廓对应的结论一致。 我们还考虑了一个沿类时测地线运动的测试粒子，并得到了第五力，该力与星系半径的倒数成比例。 此外，我们获得了对表示光偏转角度的影响以及对通过星系晕区域的光子的雷达回波延迟时间的影响。 我们表明，随着星系半径的增加，通过星系晕区域周围光的角度影响会减小。 同时，所得结果表明，相关的时间延迟随着朝向星系晕末端的半径增加而减小。 显示英文摘要

摘要： By studying the chameleon gravity on galaxy scales, we investigate the effects of the chameleon dark matter. To perform this task, we consider the dynamics of the chameleon scalar field in the region of galactic halos in static spherically symmetric spacetimes that differ only slightly from classical general relativity, but have similar symmetry behind this region. Hence, we demonstrate its ability to act as dark matter. In fact, by obtaining the expression for the tangential speed in this region, we apply this approach to explain the issue of flat galactic rotation curves. We obtain that the mass associated with the chameleon scalar field varies linearly with the radius of galaxy, and hence, the tangential speed in that region is constant, which is consistent with observational data without any need to introduce a mysterious dark matter. Accordingly, we show that the presented chameleon gravity has a well-defined Newtonian limit and can describe the geometry of spacetime in the region of flat galactic rotation curves, and is consistent with the corresponding results of the $ \Lambda CDM $ model with the NFW profile. We also consider a test particle moving in a timelike geodesic and obtain the fifth-force, which varies proportionally to the inverse of the radius of galaxy. Moreover, we obtain the effects on the angle representing the deflection of light and on the time representing the radar echo delay of photons passing through the region of galactic halos. We show that as the radius of galaxy increases, the effect on the angle of light passing through the region around galactic halos decreases. Also, the obtained result indicates that the relevant time delay decreases with increasing radius towards the end of the galactic halo.