标题： 显式微分同胚破坏，不可能条件，以及SME的引力部分 显示英文标题

标题： Explicit Diffeomorphism Breaking, No-go Conditions, and the Gravity Sector of the SME

摘要： 对在引力理论中包含显式破坏微分同胚不变性的固定非动力背景时可能出现的问题进行了简要回顾。 对标准模型扩展（SME）的影响进行了总结，包括最近的结果表明如何修改SME以适应此类固定非动力背景。 显示英文摘要

摘要： A brief recap is given of issues that can occur when fixed nondynamical backgrounds that explicitly break diffeomorphism invariance are included in gravity theories. Implications for the Standard-Model Extension (SME) are summarized, including recent results showing how the SME can be modified to accommodate such fixed nondynamical backgrounds.