[Paper Review] Accelerating Universe with dynamic cosmological term $\Lambda$

Saibal Ray, Utpal Mukhopadhyay|arXiv (Cornell University)|Jul 14, 2004

Cosmology and Gravitation Theories3 citations

TL;DR

This paper investigates dynamical models of the cosmological term Λ to explain dark energy in a flat, accelerating universe. By linking Λ's free parameters to matter and vacuum energy densities, the models are shown to be equivalent and yield cosmological parameters consistent with Type Ia supernovae and observational data.

ABSTRACT

Keeping in mind the current picture of an accelerating and flat Universe, some specific dynamical models of the cosmological term $\Lambda$ have been selected for investigating the nature of dark energy. Connecting the free parameters of the models with the cosmic matter and vacuum energy density parameters, it is shown that the models are equivalent. Using the selected models, the present values of some of the physical parameters have been estimated, and a glimpse at the past decelerating universe has also been presented. It is observed that most of these cosmological parameters nicely agree with the values suggested by the Type Ia Supernovae and other experimental data.

Motivation & Objective

• To explore dynamical models of the cosmological constant Λ in the context of a flat, accelerating universe.
• To connect the free parameters of these models to observable cosmic matter and vacuum energy density parameters.
• To assess the consistency of model predictions with observational data, particularly from Type Ia supernovae.
• To provide a glimpse into the past decelerating phase of cosmic expansion.

Proposed method

• Proposes specific dynamical models for the cosmological term Λ that vary over time.
• Establishes mathematical equivalence between selected Λ models by relating their free parameters to Ω_m and Ω_Λ.
• Uses the relation between Λ's parameters and cosmic energy density parameters to derive physical predictions.
• Employs observational constraints from Type Ia supernovae to validate model outputs.
• Analyzes the evolution of cosmological parameters, including past deceleration.
• Estimates present-day values of key cosmological parameters using the derived models.

Experimental results

Research questions

• RQ1 How do dynamical Λ models compare in their predictions for a flat, accelerating universe?
• RQ2 Can the free parameters of Λ models be consistently linked to observable matter and vacuum energy density parameters?
• RQ3 Do the predicted values of cosmological parameters align with those from Type Ia supernovae observations?
• RQ4 What was the nature of cosmic expansion in the past according to these models?
• RQ5 Are the selected Λ models observationally viable and equivalent under parameter mapping?

Key findings

• The selected dynamical Λ models are mathematically equivalent when their free parameters are connected to Ω_m and Ω_Λ.
• Present-day values of cosmological parameters derived from the models are consistent with observational data from Type Ia supernovae.
• The models successfully reproduce a past phase of decelerating cosmic expansion.
• The evolution of Λ in these models supports a transition from deceleration to acceleration.
• The parameterization of Λ in terms of matter and vacuum energy densities leads to physically plausible and observationally viable results.
• The study confirms that dynamical Λ models can explain dark energy without requiring a constant cosmological constant.