Investigating the hyperbolic and hybrid scalar field cosmologies with varying cosmological constant in $f(R,T)$ gravity
Fuente:
arXiv
Gespeichert in:
| Hauptverfasser: | , |
|---|---|
| Format: | Preprint |
| Veröffentlicht: |
2023
|
| Schlagworte: | |
| Online-Zugang: | |
| Tags: |
Tag hinzufügen
Keine Tags, Fügen Sie den ersten Tag hinzu!
|
| _version_ | 1866916319262146560 |
|---|---|
| author | Ahmed, Nasr Kamel, Tarek M. |
| author_facet | Ahmed, Nasr Kamel, Tarek M. |
| contents | This paper investigated two scalar field cosmological models in $f(R,T)$ gravity with cosmic transit and varying cosmological constant $Λ(t)$.The cosmological constant tends to have a tiny positive value in the current epoch.The scalar field pressure $p_ϕ$ shows a sign reversal for a normal scalar field. For the phantom field, the scalar potential $V(ϕ)$ is negative and the energy density $ρ_ϕ=E_k+V$ takes negative values when the equation of state parameter $ω_ϕ$ is less than $-1$. While the weak energy condition WEC implies that the total energy density $ρ=\sum_iρ_i\geq 0$, we still can have a negative $ρ$ term as long as the total $ρ$ is positive. In the current work we argue that the WEC, $ρ=\sum_i ρ_i \geq 0$ and $p_i+ρ_i \geq 0$, is not violated but with an instability for the second model at late-times. For a scalar field $ϕ$, The condition $ρ_ϕ+p_ϕ=ρ_ϕ (1+ω_ϕ)=2E_k\geq 0$ allows for $ρ_ϕ<0$ if $ω_ϕ<-1$. The causality and energy conditions have been discussed for both models.
The cosmology in both models was studied using a given function $a(t)$ derived from the desired cosmic behavior, which is the opposite of the traditional view. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2303_04076 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Investigating the hyperbolic and hybrid scalar field cosmologies with varying cosmological constant in $f(R,T)$ gravity Ahmed, Nasr Kamel, Tarek M. General Relativity and Quantum Cosmology This paper investigated two scalar field cosmological models in $f(R,T)$ gravity with cosmic transit and varying cosmological constant $Λ(t)$.The cosmological constant tends to have a tiny positive value in the current epoch.The scalar field pressure $p_ϕ$ shows a sign reversal for a normal scalar field. For the phantom field, the scalar potential $V(ϕ)$ is negative and the energy density $ρ_ϕ=E_k+V$ takes negative values when the equation of state parameter $ω_ϕ$ is less than $-1$. While the weak energy condition WEC implies that the total energy density $ρ=\sum_iρ_i\geq 0$, we still can have a negative $ρ$ term as long as the total $ρ$ is positive. In the current work we argue that the WEC, $ρ=\sum_i ρ_i \geq 0$ and $p_i+ρ_i \geq 0$, is not violated but with an instability for the second model at late-times. For a scalar field $ϕ$, The condition $ρ_ϕ+p_ϕ=ρ_ϕ (1+ω_ϕ)=2E_k\geq 0$ allows for $ρ_ϕ<0$ if $ω_ϕ<-1$. The causality and energy conditions have been discussed for both models. The cosmology in both models was studied using a given function $a(t)$ derived from the desired cosmic behavior, which is the opposite of the traditional view. |
| title | Investigating the hyperbolic and hybrid scalar field cosmologies with varying cosmological constant in $f(R,T)$ gravity |
| topic | General Relativity and Quantum Cosmology |
| url | https://arxiv.org/abs/2303.04076 |