标题： 非超对称弦的时空特性 显示英文标题

标题： Spacetime aspects of non-supersymmetric strings

摘要： 弦理论作为引力理论的一致性并不依赖于时空超对称性的存在；然而，其缺失会导致在壳世界面公式中出现 tadpole 图，从而削弱我们对物理的控制。二维共形不变性是弦理论的支柱，它要求通过 Fischler-Susskind 机制进行 tadpole 减去，其时空结果是标量 tadpole 势的出现。在本论文中，我探讨了弦理论衍生情景中超对称性缺失的几个含义。我关注的是三种十维无快子的弦理论，在这些理论中时空超对称性缺失或被破坏，研究 tadpole 势的引力后果。首先，我从奇异的一维余维真空的角度讨论真空解，探索它们的推广，并讨论它们奇异边界的特性。我基于假想超对称性的形式提出了一种对这些真空的替代观点，在这种观点中，二阶运动方程被替换为类似超对称性的的一阶方程。然后，我转向在非超对称弦模型中通过构建由电和磁通量支持的解来设计真空，并提供它们不稳定的证据。最后，我在存在 tadpole 势的情况下研究类膜解，这些解产生了具有超对称膜等距性的通量真空以及捕捉局域源反作用的引力轮廓。 显示英文摘要

摘要： The consistency of string theory as a theory of gravity does not rely on the presence of spacetime supersymmetry; however, its absence leads to the emergence of tadpole diagrams in the on-shell worldsheet formulation, thus undermining our control over the physics. Two-dimensional conformal invariance, a pillar of string theory, requires tadpole subtraction through the Fischler-Susskind mechanism, whose spacetime consequence is the emergence of scalar tadpole potentials. In this thesis, I explore several implications of the absence of supersymmetry in string-derived scenarios. I focus on the three ten-dimensional tachyon-free string theories in which spacetime supersymmetry is absent or broken, studying the gravitational consequences of tadpole potentials. First, I address vacuum solutions in terms of singular codimension-one vacua, explore their generalizations, and discuss the properties of their singular boundaries. I present an alternative perspective on these vacua based on the formalism of fake supersymmetry, in which the second-order equations of motion are replaced by supersymmetry-like first-order equations. I then turn to the topic of engineering vacua in the non-supersymmetric string models by constructing solutions that are supported by electric and magnetic fluxes and by providing evidence for their instability. Finally, I investigate brane-like solutions in the presence of tadpole potentials that yield both flux vacua with the isometries of supersymmetric branes and gravitational profiles that capture the backreaction of localized sources.