The detection of the accelerated expansion of the Universe has been one of the major breakthroughs in modern cosmology. Several cosmological probes (Cosmic Microwave Background, Supernovae Type Ia, Baryon Acoustic Oscillations) have been studied in depth to better understand the nature of the mechanism driving this acceleration, and they are being currently pushed to their limits, obtaining remarkable constraints that allowed us to shape the standard cosmological model. In parallel to that, however, the percent precision achieved has recently revealed apparent tensions between measurements obtained from different methods. These are either indicating some unaccounted systematic effects, or are pointing toward new physics. Following the development of CMB, SNe, and BAO cosmology, it is critical to extend our selection of cosmological probes. Novel probes can be exploited to validate results, control or mitigate systematic effects, and, most importantly, to increase the accuracy and robustness of our results. This review is meant to provide a state-of-art benchmark of the latest advances in emerging “beyond-standard” cosmological probes. We present how several different methods can become a key resource for observational cosmology. In particular, we review cosmic chronometers, quasars, gamma-ray bursts, standard sirens, lensing time-delay with galaxies and clusters, cosmic voids, neutral hydrogen intensity mapping, surface brightness fluctuations, stellar ages of the oldest objects, secular redshift drift, and clustering of standard candles. The review describes the method, systematics, and results of each probe in a homogeneous way, giving the reader a clear picture of the available innovative methods that have been introduced in recent years and how to apply them. The review also discusses the potential synergies and complementarities between the various probes, exploring how they will contribute to the future of modern cosmology.

Astronomy & Astrophysics (A&A) is an international journal which publishes papers on all aspects of astronomy and astrophysics

Astronomy & Astrophysics (A&A) is an international journal which publishes papers on all aspects of astronomy and astrophysics

We show that a general, exact cosmological solution, where the dynamics of a scalar field is assigned by an exponential potential, satisfies all the issues of the dark energy approach, both from a theoretical point of view and in comparison with available observational data. Moreover, tracking conditions are discussed, with a new treatment of the well known condition $\Gamma >1.\mathrm{}$ We prove that the currently used expression for $\Gamma$ is wrong.

The explanation of the accelerated expansion of the Universe poses one of the most fundamental questions in physics and cosmology today. If the accele

So far large and different data sets revealed the accelerated expansion rate of the Universe, which is usually explained in terms of dark energy. The nature of dark energy is not yet known, and several models have been introduced: a non-zero cosmological constant, a potential energy of some scalar field, effects related to the non-homogeneous distribution of matter, or effects due to alternative theories of gravity. Recently, a tension with the flat ΛCDM model has been discovered using a high-redshift Hubble diagram of supernovae, quasars, and gamma-ray bursts (GRB). Here we use the Union2 type Ia supernovae and GRB Hubble diagram, and a set of direct measurements of the Hubble parameter to explore different dark energy models. We use the Chevallier–Polarski–Linder parametrization of the dark energy equation of state, a minimally coupled quintessence scalar field, and, finally, we consider models with dark energy at early times. We perform a statistical analysis based on the Markov chain Monte Carlo method, and explore the probability distributions of the cosmological parameters for each of the competing models. We apply the Akaike Information Criterion to compare these models: our analysis indicates that an evolving dark energy, described by a scalar field with exponential potential seems to be favoured by observational data.