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Null Energy Condition and Dark Energy Models

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arxiv 0710.0115 v1 pith:3LHT6E7I submitted 2007-09-30 gr-qc astro-phhep-phhep-th

Taotao Qiu , Yi-Fu Cai , Xin-Min Zhang This is my paper · ORCID
classification gr-qcastro-phhep-phhep-th
keywords energydarkomegamodelmodelsconditiongeq-1null
verification ladder T0 review T1 audit T2 compute T3 formal
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abstract

Null Energy Condition (NEC) requires the equation of state (EoS) of the universe $w_u$ satisfy $w_u\geq-1$, which implies, for instance in a universe with matter and dark energy dominating $w_u=w_m\Omega_m+w_{de}\Omega_{de}=w_{de}\Omega_{de}\geq-1$. In this paper we study constraints on the dark energy models from the requirement of the NEC. We will show that with $\Omega_{de}\sim0.7$, $w_{de}<-1$ at present epoch is possible. However, NEC excludes the possibility of $w_{de}<-1$ forever as happened in the Phantom model, but if $w_{de}<-1$ stays for a short period of time as predicted in the Quintom theory NEC can be satisfied. We take three examples of Quintom models of dark energy, namely the phenomenological EoS, the two-scalar-field model and the single scalar model with a modified Dirac-Born-Infeld (DBI) lagrangian to show how this happens.

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Cited by 5 Pith papers

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