Dynamical Regulation of the Spin-2 Ghost: Can Hubble Friction and Quartic Buffering Permit a Non-Singular Bounce?

Standard Quadratic Gravity includes both an R2 term (the Scalaron) and a Cμνρσ2 term (the massive Spin-2 ghost). While the Scalaron is established as the driver of Starobinsky inflation, the Spin-2 mode is traditionally discarded due to unitarity violations (Ostrogradsky instability). We investigate a phenomenological model wherein the negative propagator residue of the ghost mode acts as a Pauli-Villars regulator at trans-Planckian scales. We propose two distinct stabilization mechanisms: (1) A linear "Hubble Friction" brake that operates during the high-curvature regime (H ≫ m2), and (2) A non-linear quartic self-interaction that stabilizes the vacuum in the infrared limit. We present numerical evidence suggesting that such a system can undergo a non-singular bounce, eventually settling into a disordered ghost condensate that mimics Dark Energy.