标题： 广义相对论和引力扩展理论中的双星系统 显示英文标题

标题： Twin Stars in General Relativity and Extended Theories of Gravity

摘要： 我们探讨了中子星的无重力状态方程，特别关注双星现象。我们检查了四种类别，并强调它们在广义相对论和Palatini引力中的行为。此外，我们讨论了一类I的一个子类别，在广义相对论背景下不表现出双星现象，但在修正引力中却表现出这一现象。另外，我们简要讨论了两种理论中普遍存在的能量-动量张量迹为负的问题所带来的挑战。 显示英文摘要

摘要： We explore gravity-independent equations of state for neutron stars, particularly focusing on twin stars. Examining four categories, we emphasize their behavior in both General Relativity and Palatini gravity. Additionally, we discuss a subcategory of type I, which, in the context of General Relativity, does not exhibit twin star phenomena, yet demonstrates this phenomenon in modified gravity. Furthermore, we briefly address challenges associated with the negative trace of the energy-momentum tensor, prevalent in both theories.