Abstract: The simplest ΛCDM model provides a good fit to a large span of cosmological data but harbors large areas of phenomenology and ignorance. With the improvement of the number and the accuracy of observations, discrepancies among key cosmological parameters of the model have emerged. The most statistically significant tension is the 4 sigma to 6 sigma disagreement between predictions of the Hubble constant, H (0), made by the early time probes in concert with the 'vanilla' ΛCDM cosmological model, and a number of late time, model-independent determinations of H (0) from local measurements of distances and redshifts. The high precision and consistency of the data at both ends present strong challenges to the possible solution space and demands a hypothesis with enough rigor to explain multiple observations-whether these invoke new physics, unexpected large-scale structures or multiple, unrelated errors. A thorough review of the problem including a discussion of recent Hubble constant estimates and a summary of the proposed theoretical solutions is presented here. We include more than 1000 references, indicating that the interest in this area has grown considerably just during the last few years. We classify the many proposals to resolve the tension in these categories: early dark energy, late dark energy, dark energy models with 6 degrees of freedom and their extensions, models with extra relativistic degrees of freedom, models with extra interactions, unified cosmologies, modified gravity, inflationary models, modified recombination history, physics of the critical phenomena, and alternative proposals. Some are formally successful, improving the fit to the data in light of their additional degrees of freedom, restoring agreement within 1-2 sigma between Planck 2018, using the cosmic microwave background power spectra data, baryon acoustic oscillations, Pantheon SN data, and R20, the latest SH0ES Team Riess, et al (2021 Astrophys. J. 908 L6) measurement of the Hubble constant (H (0) = 73.2 +/- 1.3 km s(-1) Mpc(-1) at 68% confidence level). However, there are many more unsuccessful models which leave the discrepancy well above the 3 sigma disagreement level. In many cases, reduced tension comes not simply from a change in the value of H (0) but also due to an increase in its uncertainty due to degeneracy with additional physics, complicating the picture and pointing to the need for additional probes. While no specific proposal makes a strong case for being highly likely or far better than all others, solutions involving early or dynamical dark energy, neutrino interactions, interacting cosmologies, primordial magnetic fields, and modified gravity provide the best options until a better alternative comes along.

Abstract: The intersection of the cosmic and neutrino frontiers is a rich field where much discovery space still remains. Neutrinos play a pivotal role in the hot big bang cosmology, influencing the dynamics of the universe over numerous decades in cosmological history. Recent studies have made tremendous progress in understanding some properties of cosmological neutrinos, primarily their energy density. Upcoming cosmological probes will measure the energy density of relativistic particles with higher precision, but could also start probing other properties of the neutrino spectra. When convolved with results from terrestrial experiments, cosmology can become even more acute at probing new physics related to neutrinos or even Beyond the Standard Model (BSM). Any discordance between laboratory and cosmological data sets may reveal new BSM physics and/or suggest alternative models of cosmology. We give examples of the intersection between terrestrial and cosmological probes in the neutrino sector, and briefly discuss the possibilities of what different laboratory experiments may see in conjunction with cosmological observatories.

Abstract: Building on the legacy of the Sloan Digital Sky Survey (SDSS-I and II), SDSS-III is a program of four spectroscopic surveys on three scientific themes: dark energy and cosmological parameters, the history and structure of the Milky Way, and the population of giant planets around other stars. In keeping with SDSS tradition, SDSS-III will provide regular public releases of all its data, beginning with SDSS Data Release 8 (DR8), which was made public in 2011 January and includes SDSS-I and SDSS-II images and spectra reprocessed with the latest pipelines and calibrations produced for the SDSS-III investigations. This paper presents an overview of the four surveys that comprise SDSS-III. The Baryon Oscillation Spectroscopic Survey will measure redshifts of 1.5 million massive galaxies and Ly alpha forest spectra of 150,000 quasars, using the baryon acoustic oscillation feature of large-scale structure to obtain percent-level determinations of the distance scale and Hubble expansion rate at z < 0.7 and at z approximate to 2.5. SEGUE-2, an already completed SDSS-III survey that is the continuation of the SDSS-II Sloan Extension for Galactic Understanding and Exploration (SEGUE), measured medium-resolution (R = lambda/lambda Delta approximate to 1800) optical spectra of 118,000 stars in a variety of target categories, probing chemical evolution, stellar kinematics and substructure, and the mass profile of the dark matter halo from the solar neighborhood to distances of 100 kpc. APOGEE, the Apache Point Observatory Galactic Evolution Experiment, will obtain high-resolution (R approximate to 30,000), high signal-to-noise ratio (S/N >= 100 per resolution element), H-band (1.51 μm < lambda < 1.70 μm) spectra of 105 evolved, late-type stars, measuring separate abundances for similar to 15 elements per star and creating the first high-precision spectroscopic survey of all Galactic stellar populations (bulge, bar, disks, halo) with a uniform set of stellar tracers and spectral diagnostics. The Multi-object APO Radial Velocity Exoplanet Large-area Survey (MARVELS) will monitor radial velocities of more than 8000 FGK stars with the sensitivity and cadence (10-40 ms(-1), similar to 24 visits per star) needed to detect giant planets with periods up to two years, providing an unprecedented data set for understanding the formation and dynamical evolution of giant planet systems. As of 2011 January, SDSS-III has obtained spectra of more than 240,000 galaxies, 29,000 z >= 2.2 quasars, and 140,000 stars, including 74,000 velocity measurements of 2580 stars for MARVELS.