On the presence of twinlike models in cosmology

TL;DR

This paper explores twinlike scalar field models in cosmology, demonstrating how they can share the same energy and pressure profiles in flat spacetime, but are incompatible with curved spacetime.

Contribution

It introduces a method to identify twinlike models using first-order equations and shows their limitations in curved spacetime scenarios.

Findings

Twinlike models exist in flat spacetime with identical energy densities and pressures.

Curvature prevents the existence of twinlike models in the studied cosmological setting.

First-order framework simplifies the search for twinlike theories.

Abstract

We study cosmological models described by a single real scalar field. We work within the first-order framework, and we show how the first-order equations simplify the investigation, leading to a direct search of twinlike theories. The procedure is used to introduce distinct models that support the same first-order equations, with the very same energy densities and pressure in flat spacetime. The presence of curvature forbids the construction of twinlike models in the cosmological scenario here investigated.