A major theoretical problem of the otherwise successful standard model (SM) is the presence of an arbitrary amount of CP violation induced by the periodic vacuum structure of Quantum Chromodynamics (known as the strong CP problem). While the most popular solution to this problem is the Peccei-Quinn mechanism, it predicts a new superllight particle, the axion, which has not been found despite extensive experimental searches. An alternative solution to this problem that does not predict an axion is one based on a parity symmetric extension of SM, which also provides a framework for understanding the neutrino masses via the seesaw mechanism. In this mini-review, I describe how minimal versions of the parity solution to strong CP require supersymmetry and how a class of SO(10) theories provide a natural grand unified (GUT) embedding of these models. These approaches have the advantage that the observed CKM CP violation emerges in a simple way in contrast to some other non-axion approaches. We discuss the importance of a search for electric dipole moment of the neutron as a way to probe these solutions.

在其他方面成功的标准模型（SM）的主要理论问题是，由量子色动力学的周期性真空结构引起的任意数量的CP违例的存在（称为强CP问题）。尽管对此问题最流行的解决方案是Peccei-Quinn机理，但它预测了一种新的超轻粒子，即轴突，尽管进行了广泛的实验研究，但仍未发现该轴突。无法预测轴力的这一问题的另一种解决方案是基于SM奇偶对称扩展的解决方案，该解决方案还提供了一种通过跷跷板机制了解中微子质量的框架。在这份小型复习中，我描述了针对强CP的奇偶校验解决方案的最小版本如何要求超对称性，以及一类SO（10）理论如何为这些模型提供自然的大统一（GUT）嵌入。这些方法的优势在于，与其他一些非轴方法相比，观察到的CKM CP违规以一种简单的方式出现。我们讨论寻找中子电偶极矩作为探测这些解决方案的重要性。