标题： 类星体在史瓦西-德西特时空中的有限距离引力透镜效应 显示英文标题

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

摘要： 我们研究了在有限距离处带有全局单极子的Schwarzschild-de Sitter黑洞的引力透镜效应。 在这种渐近非平直的时空结构中，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，第二部分来源于度规本身。 通过将宇宙学常数吸收进有效影响参数，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，我们得到了在此背景下偏折角的完整精确解。 此外，考虑到光源到观测者的距离较大，我们推导了弱场和强场极限下的光偏折角表达式。 在两种情况下，我们发现全局单极子的存在会增强偏折效应，进一步支持其作为难以捉摸的暗物质替代物的潜在作用。 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.