Cosmic Turnaround and CMB Signatures in the Unified SV0 Bounce Cosmology

This manuscript is the eleventh paper in a series establishing the Signed-Volume Effective-Fluid (SV0) model. In Paper IX, we constructed a unified cosmological history incorporating an early-universe non-singular bounce. In Paper X, we demonstrated how SV0 resolves the cosmological constant and coincidence problems. In this eleventh work, we analyze the kinematics of the bounce and its implications for the Cosmic Microwave Background (CMB). During the pre-bounce contraction phase, the universe undergoes a continuous blueshift. We show that the SV0 regularization factor ensures a smooth turnaround, preventing the blueshift from diverging at a singularity. Using the gauge-invariant perturbation theory of Paper IV, we solve the evolution of scalar perturbations across the bounce. We demonstrate that the matching conditions for the Mukhanov-Sasaki variable are well-defined and that the primordial power spectrum survives the turnaround. This provides a consistent framework in which the observed CMB anisotropies are generated during the pre-bounce contraction and naturally processed through the SV0 bounce into the post-bounce radiation era. Furthermore, the finite duration of the pre-bounce phase naturally introduces a low-l multipole cutoff, offering a distinctive observational signature. Related Works:Paper I: https://doi.org/10.5281/zenodo.24026844Paper II: https://doi.org/10.5281/zenodo.24032977Paper III: https://doi.org/10.5281/zenodo.24033838Paper IV: https://doi.org/10.5281/zenodo.24034927Paper V: https://doi.org/10.5281/zenodo.24035268Paper VI: https://doi.org/10.5281/zenodo.24035911Paper VII: https://doi.org/10.5281/zenodo.24038624Paper VIII: https://doi.org/10.5281/zenodo.24039486Paper IX: https://doi.org/10.5281/zenodo.24040648Paper X: https://doi.org/10.5281/zenodo.24046082