The Horizon–Luminosity Pinch: Resolving the Cosmological Constant Lower-Bound Problem and the Red Dwarf Paradox via Time-Symmetric Quantum Darwinism

Paper V in the Time-Symmetric Quantum Darwinism (TSQD) Series. Standard cosmology and astrobiology face two persistent fine-tuning puzzles at opposite physical scales: The Cosmological Constant Lower-Bound Problem: Weinberg’s galaxy-formation bound explains why the dimensionless vacuum energy density ΛℓP2 cannot exceed ∼ 10−120, but fails to explain why ΛℓP2 is not exponentially smaller (Λ → 0) than the observed value ΛobsℓP2 ≈ 2.9 × 10−122. The Red Dwarf (M-Dwarf) Paradox: Bayesian Copernican priors over the stellar Initial Mass Function (IMF) and main-sequence lifetimes predict with > 99% probability that technological observers should orbit long-lived, abundant M-dwarf stars (L ∼ 10−4–10−2 L☉, τMS ∼ 1011–1013 yr) rather than a rare, short-lived G2V star (L☉ ≈ 3.83 × 1026 W, τMS ≈ 1010 yr). In this fifth paper of the Time-Symmetric Quantum Darwinism (TSQD) series (doi:10.5281/zenodo.23572180, doi:10.5281/zenodo.23677536, doi:10.5281/zenodo.23818446, and doi:10.5281/zenodo.23896752), we prove that both anomalies are resolved simultaneously by a single bilateral inequality linking de Sitter horizon geometry to main-sequence nuclear astrophysics. By the Two-Stage Horizon Selection Theorem of Paper IV, overcoming Sekino–Susskind fast-scrambling on the Future Conformal Boundary (I+) requires illuminating the de Sitter event horizon area AH(Λ) = 12π/Λ with a phase-coherent photon flux φcrit ≥ 1 m−2s−1, imposing a minimum stellar power threshold Pcrit(II)(Λ) = 12πφcrithν0 / Λ. Simultaneously, clearing the evolutionary biogenesis filters (ptotal ∼ 10−22) requires a main-sequence stellar lifetime τMS(Lhost) ≥ Δτbio ≈ 4.5 Gyr, imposing a strict upper luminosity ceiling Lhost ≤ Lmax,bio ≈ 1 L☉. Requiring Pcrit(II)(Λ) ≤ Lhost ≤ Lmax,bio simultaneously prunes M-dwarf branches as sub-saturating (fA ∼ 10−3 ≪ 1), fixes the lower bound of the cosmological constant at Λmin = 12πφcrithν0 / L☉ ≈ 1.1 × 10−52 m−2 (ΛminℓP2 ≈ 2.9 × 10−122), and pinches the winning cosmic trunk onto a G2V solar-mass star. Complete Series Links: Paper I: Cosmic Fixed-Point Einselection: A Time-Symmetric Quantum Darwinist Resolution of the Measurement Problem — 10.5281/zenodo.23572180 Paper II: The Cosmic Return Stroke: Resolving the Fermi Paradox via Time-Symmetric Quantum Amplification — 10.5281/zenodo.23677536 Paper III: Foundational Consistency of Time-Symmetric Quantum Darwinism: No-Signaling, Relativistic Covariance, and Born-Rule Recovery — 10.5281/zenodo.23818446 Paper IV: De Sitter Horizon Freeze-Out and the Physical Threshold of Cosmic Einselection: From Planetary Radar to Post-Biological Horizon Saturation — 10.5281/zenodo.23896752 Paper V: The Horizon–Luminosity Pinch: Resolving the Cosmological Constant Lower-Bound Problem and the Red Dwarf Paradox via Time-Symmetric Quantum Darwinism (Present Work)