The R_h=ct Universe Without Inflation

TL;DR

This paper shows that the R_h=ct universe model naturally resolves the horizon problem without requiring inflation, unlike standard cosmological models, by demonstrating causal connectivity from the universe's inception.

Contribution

It provides a fundamental analysis of photon propagation in the R_h=ct universe, proving the horizon problem does not arise in this model and challenging the necessity of inflation.

Findings

Horizon problem only appears in certain FRW cosmologies like LCDM.

In R_h=ct universe, causal connection exists from the universe's beginning.

Inflation is not necessary to explain the uniformity of the cosmic microwave background.

Abstract

The horizon problem in the standard model of cosmology (LDCM) arises from the observed uniformity of the cosmic microwave background radiation, which has the same temperature everywhere (except for tiny, stochastic fluctuations), even in regions on opposite sides of the sky, which appear to lie outside of each other's causal horizon. Since no physical process propagating at or below lightspeed could have brought them into thermal equilibrium, it appears that the universe in its infancy required highly improbable initial conditions. In this paper, we examine this well-known problem by considering photon propagation through a Friedmann-Robertson-Walker (FRW) spacetime at a more fundamental level than has been attempted before, demonstrating that the horizon problem only emerges for a subset of FRW cosmologies, such as LCDM, that include an early phase of rapid deceleration. We show that the horizon problem is nonexistent for the recently introduced R_h=ct universe, obviating the principal motivation for the inclusion of inflation. We demonstrate through direct calculation that, in the R_h=ct universe, even opposite sides of the cosmos have remained causally connected to us - and to each other - from the very first moments in the universe's expansion. Therefore, within the context of the R_h=ct universe, the hypothesized inflationary epoch from t=10^{-35} seconds to 10^{-32} seconds was not needed to fix this particular "problem", though it may still provide benefits to cosmology for other reasons.