No Cosmological Horizon Conjecture (NCHC)

Determine whether solutions of quantum gravity in spacetime dimension d≥3 can ever possess a cosmological event horizon, i.e., prove or disprove the conjecture that such solutions never admit a finite event-horizon distance d_e.

Background

The NCHC was introduced to capture the idea that quantum-gravity solutions should not exhibit cosmological event horizons, motivated by difficulties in formulating holography and S-matrix observables in de Sitter space.

The review revisits NCHC in the context of asymptotic acceleration and discusses its phenomenological implications for cosmology; nonetheless, it remains an unproven conjecture.