# Generalized phenomenological models of dark energy

## TL;DR

This paper proposes two phenomenological models of dark energy within General Relativity, where the cosmological constant varies with the scale factor's acceleration and matter density, fitting observational data without field-theoretic assumptions.

## Contribution

It introduces two new phenomenological models of dark energy based on the variation of the cosmological constant with acceleration and density, constrained by recent observational data.

## Key findings

- Models fit observational data satisfactorily
- Dynamical cosmological constant explains recent acceleration
- No field-theoretic interpretation needed

## Abstract

It was first observed at the end of the last century that the universe is presently accelerating. Ever since, there have been several attempts to explain this observation theoretically. There are two possible approaches. The more conventional one is to modify the matter part of the Einstein Field Equations and the second one is to modify the geometry part. We shall consider two phenomenological models based on the former, more conventional approach within the context of General Relativity. The phenomenological models in this paper consider a $\Lambda$ term as a function of $\frac{\ddot{a}}{a}$ and $\rho$ where $a$ and $\rho$ are the scale factor and matter-energy density respectively. Constraining the free parameters of the models with latest observational data gives satisfactory values of parameters as considered by us initially. Without any field-theoretic interpretation, we explain the recent observations with a dynamical cosmological constant.