On geometry and symmetries in gauge gravity: Cartan connection approach

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Our earlier findings indicate the violation of the 'volume simplicity' constraint in the current Spinfoam models (EPRL-FK-KKL). This result, and related problems in LQG, promted to revisit the metric/vielbein degrees of freedom in the classical Einstein-Cartan gravity. Notably, I address in detail what constitutes a 'geometry' and its 'group of motions' in such Poincare gauge theory. In a differential geometric scheme that I put forward the local translations are not broken but exact, and their relation to diffeomorphism transformations is clarified. The refined notion of a tensor takes into account the (relative) localization in spacetime, whereas the key concept of 'development' generalizes parallel transport (of vectors and points) to affine spaces. I advocate for this Cartan connection as the fundamental d.o.f. of the gravitational field, and discuss implications for discretization and quantization. Based on [1905.06931].