Related papers: Reconstructing and Deconstructing Dark Energy
Within the context of standard cosmology, an accelerating universe requires the presence of a third `dark' component of energy, beyond matter and radiation. The available data, however, are still deemed insufficient to distinguish between…
The fact that the energy densities of dark energy and matter are similar currently, known as the coincidence problem, is one of the main unsolved problems of cosmology. We present here a model in which a spatial curvature of the universe…
Early dark energy, as a proposed solution to the Hubble tension, faces an additional "why now" problem. Why should dark energy emerge just prior to recombination, billions of years before the onset of cosmic acceleration? Assisted…
Using recent precision measurements of cosmological paramters, we re-examine whether these observations alone, independent of type Ia supernova surveys, are sufficient to imply the existence of dark energy. We find that best measurements of…
The expansion of the Universe is understood to have accelerated during two epochs: in its very first moments during a period of Inflation and much more recently, at $z < 1$, when Dark Energy is hypothesized to drive cosmic acceleration. The…
We perform an empirical consistency test of General Relativity/dark energy by disentangling expansion history and growth of structure constraints. We replace each late-universe parameter that describes the behavior of dark energy with two…
Observations of clusters of galaxies that gravitationally lens faint background galaxies can probe the amount and the equation of state, $\5$, of the dark energy (quintessence) in the universe. Provided that the mass profile and the mass…
If the dark energy equation of state is anisotropic, the expansion rate of the universe becomes direction-dependent at late times. We show that such models are not only cosmologically viable but that they could explain some of the observed…
One of the most important and surprising discoveries in cosmology in recent years is the realization that our Universe is dominated by a mysterious dark energy, which leads to an accelerating expansion of space-time. A simple generalization…
In order to depict the transition from deceleration to acceleration expansion of the universe we use a power-law expansion scale factor, $a\sim t^{n_0+bt^m}$, with $n_0$, $b$ and $m$ three parameters determined by $H_0$, $q_0$ and $z_T$.…
Recent observations from the Dark Energy Spectroscopic Instrument (DESI 2025) indicate a weakening of cosmic acceleration at low redshifts $z < 1$, with effective dark energy equation of state parameters $w_0 > -1$ and $w_a < 0$. We…
In this work we review briefly the origin and history of the cosmological constant and its recent reincarnation in the form of the dark energy component of the universe. We also comment on the fundamental problems associated to its…
Dark energy is a premier mystery of physics, both theoretical and experimental. As we look to develop plans for high energy physics over the next decade, within a two decade view, we consider benchmarks for revealing the nature of dark…
We revisit a cosmological model where dark matter (DM) and dark energy (DE) follow barotropic equations of state, allowing deviations from the standard $\Lambda$CDM framework (i.e. $w_{dm} \neq 0$, $w_{de} \neq -1$), considering both flat…
Observations provide increasingly strong evidence that the universe is accelerating. This revolutionary advance in cosmological observations confronts theoretical cosmology with a tremendous challenge, which it has so far failed to meet.…
We examine flat models containing a dark matter component and an arbitrary dark energy component, subject only to the constraint that the dark energy satisfies the weak energy condition. We determine the constraints that these conditions…
We present the data-driven reconstruction of gravitational theories and Dark Energy models on cosmological scales. We showcase the power of present cosmological probes at constraining these models and quantify the knowledge of their…
One of the goals of current cosmological studies is the determination of the expansion and acceleration rates of the universe as functions of redshift, and the determination of the properties of the dark energy that can explain these…
The nature of dark energy (DE) remains elusive, even though it constitutes the dominant energy-density component of the Universe and drives the late-time acceleration of cosmic expansion. By combining measurements of the expansion history…
A fundamental question in cosmology is whether dark energy evolves over time, a topic that has gained prominence since the discovery of cosmic acceleration. Recently, the DESI collaboration has reported increasing evidence for evolving dark…