The Apparent (Gravitational) Horizon in Cosmology

Abstract

In general relativity, a gravitational horizon (more commonly known as the "apparent horizon") is an imaginary surface beyond which all null geodesics recede from the observer. The Universe has an apparent (gravitational) horizon, but unlike its counterpart in the Schwarzschild and Kerr metrics, it is not static. It may eventually turn into an event horizon---an asymptotically defined membrane that forever separates causally connected events from those that are not---depending on the equation of state of the cosmic fluid. In this paper, we examine how and why an apparent (gravitational) horizon is manifested in the Friedmann-Robertson-Walker metric, and why it is becoming so pivotal to our correct interpretation of the cosmological data. We discuss its observational signature and demonstrate how it alone defines the proper size of our visible Universe. In so doing, we affirm its physical reality and its impact on cosmological models.

24 pages, 1 figure. Accepted for publication in AJP

References in corpus (8)

• The region with trapped surfaces in spherical symmetry, its core, and their boundaries
• Cosmological apparent and trapping horizons
• Outer Trapped Surfaces in Vaidya Spacetimes
• Adventures in Friedmann Cosmology: An Educationally Detailed Expansion of the Cosmological Friedmann Equations
• Is space expanding in the Friedmann universe models?
• A direct consequence of the expansion of space?
• Interpretation of the Cosmological Metric
• Cosmological Tests with the FSRQ Gamma-ray Luminosity Function

Cited by in corpus (21)

• The Cosmic Timeline Implied by the JWST High-redshift Galaxies
• Model Comparison of $\Lambda$CDM vs $R_h=ct$ using Cosmic Chronometers
• Thermodynamics of the FLRW apparent horizon
• A Solution to the electroweak horizon problem in the R_h=ct universe
• Quantum Fluctuations at the Planck Scale
• Thermodynamics of the R_h=ct Universe: A Simplification of Cosmic Entropy
• Classicalization of Quantum Fluctuations at the Planck Scale in the R_h=ct Universe
• Generalized Entropy Implies Varying-G: Horizon Area Dependent Field Equations and Black Hole-Cosmology Coupling
• Missing large-angle correlations versus even-odd point-parity imbalance in the cosmic microwave background
• A Resolution of the Monopole Problem in the R_h=ct Universe
• A resolution of the Trans-Planckian problem in the R_h=ct universe
• An exact model for evaporating primordial black holes in cosmological space-time
• The Electroweak Horizon Problem
• A Pop III generated dust screen at z~16
• Tantalizing New Physics from the Cosmic Purview
• A Cosmological basis for E=mc^2
• The Anomalous 21-cm Absorption at High Redshifts
• Tensor Fluctuations in the Early Universe
• A Comparative Test of the LCDM and R_h=ct Cosmologies Based on Upcoming Redshift Drift Measurements
• Finite time pseudo-rip singularity in cosmology
• Black shells and naked shells