标题： Schwarzschild-de Sitter时空中的有限距离全球单极子的引力透镜效应 显示英文标题

标题： Finite-Distance Gravitational Lensing of a Global Monopole in Schwarzschild-de Sitter Spacetime

摘要： 我们研究了有限距离处具有全局单极子的Schwarzschild-de Sitter黑洞的引力透镜效应。 在这个渐近非平坦时空里，光的偏折角被分解为两部分：第一部分来源于轨道微分方程，第二部分源自度规本身。 通过将宇宙常数吸收进有效冲击参数，我们利用椭圆积分推导出第一部分的解析表达式。 结合第二部分后，我们在该背景下得到了完整的偏折角精确解。 此外，考虑到源到观测者之间的距离较大，我们分别推导了弱场和强场极限下光的偏折角表达式。 在两种情况下，我们都发现全局单极子的存在增强了偏折效应，进一步支持了它作为暗物质替代物的潜在角色。 显示英文摘要

摘要： We investigate the gravitational lensing of a Schwarzschild-de Sitter black hole with a global monopole at finite distances. In this asymptotically nonflat spacetime, the deflection angle of light is decomposed into two parts: the first derives from the orbit differential equation, and the second originates from the metric itself. By absorbing the cosmological constant into the effective impact parameter, we derive an analytical expression for the first part using elliptic integrals. Combined with the second part, we obtain a complete exact solution for the deflection angle in this context. Additionally, considering that the distances from the source to the observer are large, we derive expressions for the light deflection angle in both the weak and strong field limits. In both cases, we find that the deflection is enhanced by the presence of the global monopole, further supporting its potential role as an alternative to elusive dark matter.