Unveiling the Universe with Emerging Cosmological Probes
  The detection of the accelerated expansion of the Universe has been one of
the major breakthroughs in modern cosmology. Several cosmological probes (CMB,
SNe Ia, BAO) 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, 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.
