Natural Emergence of LCDM Cosmology within General Relativity from Two Alternative Frameworks Without Fine-Tuning and Coincidence

TL;DR

This paper demonstrates how the LCDM cosmology naturally emerges within standard General Relativity through a symmetry-breaking mechanism related to the cosmological constant, addressing fine-tuning and coincidence issues without exotic components.

Contribution

It introduces a novel framework where LCDM cosmology arises from intrinsic matter dynamics and symmetry breaking, eliminating the need for fine-tuning or exotic fields.

Findings

Reproduces LCDM expansion history without negative-pressure components

Alleviates fine-tuning and coincidence problems in cosmology

Shows symmetry-breaking in matter leads to late-time acceleration

Abstract

In this study, by revisiting the quantum interpretation of the cosmological constant, we introduce its formal representation within standard General Relativity. Examining its behavior in a Friedmann-Robertson-Walker spacetime reveals a mechanism in which the symmetry between energy and momentum is dynamically broken. Applying this concept naturally leads to the derivation of the familiar LCDM model, while simultaneously alleviating both the fine-tuning and coincidence problems. Comparison of the ground-state energy behavior in the Friedmann equations with a dust matter field further indicates that large-scale matter exhibits the same symmetry-breaking behavior. Remarkably, due to this broken symmetry, the interactions between local regions of matter in the large-scale structure generate effective pressure, driving late-time acceleration and reproducing the LCDM expansion history without invoking exotic fields or negative-pressure components. This framework provides a self-consistent realization of LCDM within General Relativity, emerging entirely from the intrinsic dynamics of standard matter without fine-tuning and coincidence problems.