Physical Basis for the Symmetries in the Friedmann-Robertson-Walker Metric

Abstract

Modern cosmological theory is based on the Friedmann--Robertson--Walker (FRW) metric. Often written in terms of co-moving coordinates, this well-known solution to Einstein's equations owes its elegant and highly practical formulation to the cosmological principle and Weyl's postulate, upon which it is founded. However, there is physics behind such symmetries, and not all of it has yet been recognized. In this paper, we derive the FRW metric coefficients from the general form of the spherically symmetric line element and demonstrate that, because the co-moving frame also happens to be in free fall, the symmetries in FRW are valid only for a medium with zero active mass. In other words, the spacetime of a perfect fluid in cosmology may be correctly written as FRW only when its equation of state is rho+3p=0, in terms of the total pressure p and total energy density rho. There is now compelling observational support for this conclusion, including the Alcock--Paczynski test, which shows that only an FRW cosmology with zero active mass is consistent with the latest model-independent baryon acoustic oscillation data.

7 Pages. Final published version

References in corpus (2)

• Improved Cosmological Constraints from New, Old and Combined Supernova Datasets
• Baryon Acoustic Oscillations in the Lyα forest of BOSS DR11 quasars

Cited by in corpus (39)

• A comparison of the R_h=ct and LCDM cosmologies using the Cosmic Distance Duality Relation
• The Linear Growth of Structure in the R_h=ct Universe
• The Zero Active Mass Condition in Friedmann-Robertson-Walker Cosmologies
• The HII Galaxy Hubble Diagram Strongly Favors $R_{\mathrm{h}}=ct$ over $\Lambda$CDM
• Model Selection Using Cosmic Chronometers with Gaussian Processes
• The Apparent (Gravitational) Horizon in Cosmology
• Evidence of a truncated spectrum in the angular correlation function of the cosmic microwave background
• Model Comparison of $\Lambda$CDM vs $R_h=ct$ using Cosmic Chronometers
• Power law cosmology model comparison with CMB scale information
• Cosmological test with the QSO Hubble diagram
• Impact of a locally measured H_0 on the interpretation of cosmic chronometer data
• Definitive Test of the R_h=ct Universe Using Redshift Drift
• Thermodynamics of massless particles in curved spacetime
• Model Selection with Strong-lensing Systems
• Primordial Nucleosynthesis in the Rh = ct cosmology: Pouring cold water on the Simmering Universe
• A Solution to the electroweak horizon problem in the R_h=ct universe
• A Distance-Deviation Consistency and Model-Independent Method to Test the Cosmic Distance-Duality Relation
• The Maximum Angular-Diameter Distance in Cosmology
• Analyzing H(z) Data using Two-point Diagnostics
• Cosmological Tests with the FSRQ Gamma-ray Luminosity Function
• Cosmological Tests With Strong Gravitational Lenses using Gaussian Processes
• Friedmann-Robertson-Walker models do not require zero active mass
• A Two-point Diagnostic for the HII Galaxy Hubble Diagram
• Cosmological Tests with the Joint Lightcurve Analysis
• A Cosmological Solution to the Impossibly Early Galaxy Problem
• A comparison of the R_h=ct and LCDM cosmologies based on the observed halo mass function
• J1342+0928 Supports the Timeline in the R_h=ct Cosmology
• Reassessing Dust's Role in Forming the CMB
• A resolution of the Trans-Planckian problem in the R_h=ct universe
• Puzzling initial conditions in the R_h=ct model
• What if the universe expands linearly? A local general relativity to solve the "zero active mass" problem
• Model Selection based on the Angular-Diameter Distance to the Compact Structure in Radio Quasars
• Tantalizing New Physics from the Cosmic Purview
• Assessing Cosmic Acceleration with the Alcock-Paczynski Effect in the SDSS-IV Quasar Catalog
• A Cosmological basis for E=mc^2
• A Comparative Test of the LCDM and R_h=ct Cosmologies Based on Upcoming Redshift Drift Measurements
• The Anomalous 21-cm Absorption at High Redshifts
• Comparison of $\Lambda$CDM and $R_h=ct$ with updated galaxy cluster $f_{gas}$ measurements using Bayesian inference
• Cosmological test using the high-redshift detection rate of FSRQs with the Square Kilometer Array