Expanding on our prior efforts to search for Lorentz invariance violation (LIV) using the linear optical polarimetry of extragalactic objects, we propose a new method that combines linear and circular polarization measurements. While existing work has focused on the tendency of LIV to reduce the linear polarization degree, this new method additionally takes into account the coupling between photon helicities induced by some models. This coupling can generate circular polarization as light propagates, even if there is no circular polarization at the source. Combining significant detections of linear polarization of light from extragalactic objects with the absence of the detection of circular polarization in most measurements results in significantly tighter constraints regarding LIV. The analysis was carried out in the framework of the Standard-Model Extension (SME), an effective field theory framework to describe the low-energy effects of an underlying fundamental quantum gravity theory. We evaluate the performance of our method by deriving constraints on the mass dimension $d=4$ CPT-even SME coefficients from a small set of archival circular and linear optical polarimetry constraints and compare them to similar constraints derived in previous works with far larger sample sizes and based on linear polarimetry only. The new method yielded constraints that are an order of magnitude tighter even for our modest sample size of 21 objects. Based on the demonstrated gain in constraining power from scarce circular data, we advocate for the need for future extragalactic circular polarization surveys.

中文翻译：

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银河系源线性和圆形光学偏振联合对洛伦兹不变性的新约束

在扩展我们先前使用河外物体的线性光学偏振法搜索洛伦兹不变性违反（LIV）的努力的基础上，我们提出了一种结合线性和圆偏振测量的新方法。虽然现有的工作集中在LIV降低线性极化程度的趋势上，但这种新方法还考虑了某些模型引起的光子螺旋度之间的耦合。即使在光源处没有圆偏振，这种耦合也会在光传播时产生圆偏振。在大多数测量中，将来自银河外物体的光的线性偏振的显着检测与不检测圆偏振相结合，会导致有关LIV的约束更加严格。该分析是在标准模型扩展（SME）的框架内进行的，该模型是一种有效的场论框架，用于描述基础量子引力理论的低能效应。我们通过推导质量维数约束来评估我们方法的性能$d=4$CPT甚至SME系数都来自一小套归档圆和线性光学偏振约束，并将它们与以前的工作中得出的类似约束进行了比较，后者的样本量大得多，并且仅基于线性偏振。即使对于我们21个对象的适度样本大小，新方法所产生的约束也要严格一个数量级。基于稀缺圆形数据显示的约束力增益的证明，我们提倡将来有必要进行银河系外圆极化调查。