Related papers: Crossing the phantom divide in scalar-tensor and v…
In generalized Proca theories, characterized by a vector field with broken $U(1)$ gauge invariance, late-time cosmic acceleration can be realized with a dark energy equation of state in the regime $w_{\rm DE} < -1$. In such scenarios,…
Recently, type Ia supernovae data appear to support a dark energy whose equation of state $w$ crosses -1, which is a much more amazing problem than the acceleration of the universe. We show that it is possible for the equation of state to…
The cosmic acceleration is one of the most significant cosmological discoveries over the last century. Following the more accurate data a more dramatic result appears: the recent analysis of the observation data (especially from SNe Ia)…
Recent findings from the Dark Energy Spectroscopic Instrument (DESI), analyzed together with supernova observations and CMB measurements, provide statistically significant indications (at the 2-5$\sigma$ level) of a time-varying dark energy…
There is accumulating observational evidence (based on SnIa data) that the dark energy equation of state parameter $w$ may be evolving with time and crossing the phantom divide barrier $w=-1$ at recent times. The confirmation of these…
Cosmology where the effective dark energy crosses $w=-1$ can be realized in Horndeski gravity with shift symmetric terms plus a linear potential. We highlight the special role of the nearly conserved scalar charge. The theory is highly…
The $\Lambda$CDM model is a remarkably successful model which is consistent with the observations of cosmic microwave background radiation (CMB), baryon acoustic oscillation (BAO), and large scale structure of the Universe. However, the…
If the dark energy equation of state parameter w(z) crosses the phantom divide line w=-1 (or equivalently if the expression d(H^2(z))/dz - 3\Omega_m H_0^2 (1+z)^2 changes sign) at recent redshifts, then there are two possible cosmological…
Recently a lot of attention has been given to building dark energy models in which the equation-of-state parameter $w$ can cross the phantom divide $w=-1$. However, to our knowledge, these models with crossing the phantom divide only…
We develop a two-scalar field quintom model, which utilises both a quintessence-like and a phantom-like scalar field, enabling a smooth and stable transition across the $w=-1$ phantom divide as hinted by recent measurements of Baryonic…
Recent cosmological data, including DESI DR2, highlight significant tensions within the $\Lambda$CDM paradigm. When analyzed in the context of General Relativity (GR), the latest DESI data favor a dynamical dark energy (DDE) equation of…
Recent results from the Dark Energy Spectroscopic Instrument (DESI) provide evidence for a dynamical dark-energy component, whose equation of state appears to have recently crossed the phantom divide. In this Letter, we present an…
Dark energy constraints have forced viable alternatives that differ substantially from a cosmological constant Lambda to have an equation of state w that evolves across the phantom divide set by Lambda. Naively, crossing this divide makes…
One possible way to explain the observed effective dark energy equation of state crossing $w=-1$ (the phantom divide) is through modified gravity. A key point is to not view the expansion history in isolation but to take into account the…
Current cosmological data seem to show that dark energy is evolving in time and that it possibly crossed the phantom divide in the past. So far the only theories that lead to such a behavior involve a non-trivial coupling between dark…
Recent results from DESI BAO measurements, together with Planck CMB and Pantheon+ data, suggest that there may be a `phantom' phase ($w_{\rm de}<-1$) in the expansion of the Universe. This inference follows when the $w_0, w_a$…
Motivated by recent results from the DESI collaboration, we explore two classes of quintessence models that can give rise to crossing of the dark energy equation of state through the ``phantom divide'' $w=-1$. These are models with…
Motivated by the recent Dark Energy Spectroscopic Instrument (DESI) DR2 preference for dynamical dark energy, we study interacting dark energy models in which a canonical quintessence field couples to cold dark matter through a…
Recent data from DESI Year 2 BAO, Planck CMB, and various supernova compilations suggest a preference for evolving dark energy, with hints that the equation of state may cross the phantom divide line ($w = -1$). While this behavior is seen…
Within the framework of spatially covariant theories, we propose a general model for dark energy (DE) in which the cosmological background and perturbations are independently controlled by different sets of coefficients, and the equation of…