Meysam Motaharfar, Parampreet Singh

Loop quantum cosmology based on Thiemann's regularization procedure leads to the resolution of the big bang singularity and bounce in the isotropic setting. A key distinction from standard loop quantum cosmology is that, in this framework, either the pre-bounce or post-bounce epoch is necessarily characterized by an emergent Planckian de Sitter phase. In this work we explore the Planckian physics of Thiemann regularized loop quantization of the Bianchi-I spacetimes. We show that as in the isotropic model, there exists an emergent de Sitter phase which naturally dampens anisotropic shear and removes cosmic hair. However, this isotropization comes at a steep price: although a macroscopic post-bounce regime is achieved, the universe never becomes truly classical. We further demonstrate that this isotropization mechanism is non-generic. These results help clarify and reinterpret recent results by Gan et al. [1] that, in anisotropic Thiemann regularized loop quantum cosmology, quantum gravity effects generically damp anisotropic shear in a way that is independent of initial conditions and the matter content, and that this anisotropic shear damping mechanism arises from a novel quantum gravity effect. Our work explains the origin of this mechanism and its limitations.