Time Variable Cosmological Constants from Cosmological Horizons

TL;DR

This paper explores time-variable cosmological constants derived from different cosmological horizons, analyzing their equations of state and compatibility with current observations, revealing that some models align with holographic principles while others are less viable.

Contribution

It introduces horizon-based, time-variable cosmological constants and compares their properties and observational viability, extending previous static models.

Findings

Hubble horizon-based model exhibits quintessence-like behavior.

Particle horizon model conflicts with current cosmological observations.

Future event horizon model aligns with holographic dark energy but differs in evolution due to interactions.

Abstract

In this paper, motivated from the fact that a de Sitter cosmological boundary corresponds to a positive cosmological constant, we consider time variable cosmological constants, dubbed {\it horizon cosmological constants}. The horizon cosmological constants correspond to Hubble horizon, future event horizon and particle horizon are discussed respectively. When the Hubble horizon is taken as a cosmological length scale, the effective equation of state of horizon cosmological constant is quintessence-like. The values of model parameter $c$ will determine the current status of our universe. When particle horizon is taken as the cosmological length scale, non viable cosmological model can be obtained for the requirement of $\Omega_{\Lambda}<1/3$ which conflicts with current comic observations. When the future event horizon is taken as the role of cosmological length scale, the forms of effective equation of state of horizon cosmological constants are the the same as the holographic ones. But, their evolutions are different because of the effective interaction with cold dark matter.