Dark energy–matter equivalence by the evolution of cosmic equation of state

Alfano A.C. Cafaro C. Capozziello S. Luongo O.
December 2023 Elsevier B.V.

Physics of the Dark Universe
2023 #42

We consider a model-independent approach to constrain the equivalence redshift, z_eq, at which dark energy and the total matter (cold dark matter and baryonic) equate their magnitudes. To this aim, in the context of a homogeneous and isotropic universe, we first consider a generic model where the dark energy contribution is provided by an unknown function of barotropic fluids. Afterwards, we compute the deceleration and jerk parameters, evaluating at our epoch, namely z=0, and at z=z_eq. Thus, by Taylor expanding around current time the Hubble rate, luminosity and angular distances, we substitute the theoretical expressions obtained from the aforementioned generic dark energy model, defining a correspondence between quantities evaluated at z=0 and z=z_eq. In so doing, we directly fit these quantities by means of current data sets, involving the most recent Pantheon type Ia supernovae, baryonic acoustic oscillation and Hubble rate points. We consider two hierarchies in our fitting procedures and compare our findings in the spatially-flat universe first and including spatial curvature, later. We assess constraints on the overall equation of state of the universe and its first derivative. We compare our results with those predicted by the standard ΛCDM paradigm. Specifically, our findings are in agreement at the 2σ confidence level, assuming a constant dark energy term. However, our analysis does not rule out the possibility of a slight evolution of dark energy, indicating a small deviation from the scenario of a pure cosmological constant. In particular, the possible departures appear consistent with a phenomenological ωCDM model, rather than more complicated dark energy parameterizations.

Cosmography , Dark energy reconstruction , Equivalence redshift

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Dipartimento di Fisica, “E. Pancini”, Universita’ “Federico II” di Napoli, Via Cinthia, Napoli, I-80126, Italy
SUNY Polytechnic Institute, 257 Fuller Road, Albany, 12203, NY, United States
Scuola Superiore Meridionale, Largo S. Marcellino 10, Napoli, I-80138, Italy
INFN, Sezione di Napoli, Via Cinthia, Napoli, I-80126, Italy
Università di Camerino, Divisione di Fisica, Via Madonna delle carceri 9, Camerino, 62032, Italy
SUNY Polytechnic Institute, Utica, 13502, NY, United States
INFN, Sez. di Perugia, Perugia, 06123, Italy
INAF - Osservatorio Astronomico di Brera, Milano, Italy
NNLOT, Al-Farabi Kazakh National University, Al-Farabi av. 71, Almaty, 050040, Kazakhstan

Dipartimento di Fisica
SUNY Polytechnic Institute
Scuola Superiore Meridionale
INFN
Università di Camerino
SUNY Polytechnic Institute
INFN
INAF - Osservatorio Astronomico di Brera
NNLOT

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