Cosmology and Particle Physics at the Intersection of Theory and Experiment

This award funds the research of Professor Luis Anchordoqui at CUNY Lehman College.

High energy physics is in a state of flux. Data from underground particle colliders, from astrophysics, and from cosmology are together allowing physicists to determine with unprecedented accuracy the values of the many parameters that describe our universe. The values of these parameters are turning out to be the keys to unlocking fundamental secrets concerning the evolution of the universe.

One of the most prominent parameters describing the universe is the so-called Hubble constant H0, which quantifies how rapidly the universe is expanding today. Unfortunately, recent improved measurements of this quantity have led to a mystery, with the apparent value of H0 depending on how it is measured. Physicists using the Planck satellite to study the light from the "early" universe (only about 380,000-years after the big bang) reported that H0 should be about 67 (shorthand for the universe is expanding some 67 kilometers per second faster every 3.26 million light-years), while physicists analyzing astronomical observations from stars and galaxies in the "late" universe peg H0 at about 73.

The discrepancy between these two values of H0 is called the "Hubble constant tension". The resolution of this conundrum will likely require a coordinated effort involving theory, interpretation, data analysis, and observation. In this dynamic environment, Professor Anchordoqui will study methods that can help address the H0 tension while at the same time providing solid predictions for data from underground colliders.

Research in this area thus advances the national interest by promoting the progress of fundamental science. Professor Anchordoqui will also involve students in his research, thereby helping to train the next generation of scientists.

More technically, Professor Anchordoqui will pursue a number of different approaches to addressing the Hubble constant tension. These include theoretical modeling of a transition from an anti-de Sitter (AdS) to a de Sitter (dS) space in the late universe, which has recently been proposed as an empirical solution of the H0 tension. The theoretical modelling is rooted on quantum effects derived from the Casimir energy of a scalar and fermions propagating into one extra ("dark") dimension of a size in the micron range.

In particular, Anchordoqui will study the problem of false vacuum decay in the presence of gravity and one compact dimension, and compute the transition probability of the scalar field (which triggers the AdS-dS transition), generalizing the reults of Coleman and de Luccia. In addition, he will investigate aspects of primordial black holes within the dark dimension scenario.

Anchordoqui will also carry out statistical analyses using Monte Carlo Markov Chain methods to constrain cosmological parameters which arise in minimal extensions of the empirical AdS-dS transition model, as well as in explicit stringy realizations of the Dynamical Dark Matter framework. Professor Anchordoqui is also involved with the Pierre Auger Collaboration, searching for the origin and nature of the highest-energy cosmic rays and studying particle interactions at center-of-mass energies well beyond those attained at the LHC.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.