The Big Spin Cosmology: A Spin-Torsion Rotating Bounce Model Connecting Kerr Black Holes, Einstein-Cartan Gravity and the Origin of the Universe

We present the Big Spin cosmological framework, a rotating non-singular bounce model formulated within Einstein-Cartan-Sciama-Kibble gravity. Unlike the standard inflationary paradigm, the present model attributes the origin of the observable Universe to the gravitational collapse of an interior rotating Kerr geometry whose singularity is avoided through spin-torsion interactions. The intrinsic spin of fermionic matter sources spacetime torsion, producing an effective ultra-stiff fluid with energy density proportional to a⁻⁶. This repulsive component naturally generates a cosmological bounce, preventing curvature singularities without introducing an inflaton field. A conserved cosmological vorticity is incorporated through the Raychaudhuri equation, leading to a modified Friedmann equation containing a rotational potential proportional to a⁻⁴. The resulting frame-dragging geometry defines an extended rotational particle horizon capable of establishing large-scale causal contact without requiring superluminal expansion. The transition between the collapsing Kerr interior and the expanding FLRW universe is modeled using generalized Darmois-Israel junction conditions. The framework predicts several potentially observable signatures, including residual cosmic vorticity, parity-violating primordial B-mode polarization, chiral gravitational waves, and low-multipole corrections in the Cosmic Microwave Background. The Big Spin model provides a unified geometric description linking black-hole interiors, torsion gravity, cosmological bounce dynamics, and the large-scale structure of the Universe while remaining compatible with local Lorentz invariance.