Theory Group for Quarks, Hadrons, and Nuclei

Welcome to the Theoretical Quarks, Hadrons, and Nuclei (TQHN) Research Group at the University of Maryland. We conduct research in quantum chromodynamics, lattice QCD, perturbative QCD, chiral perturbation theory, effective field theories, dense quark matter, neutrino physics, dark matter, and large Nc. We are also part of the Maryland Center for Fundamental Physics, along with the Elementary Particle Physics and Gravitation Research groups.


Lattice QCD

Lattice quantum chromodynamics is the dominant method for simulating QCD. Lattice studies of nuclear systems, matches to low-energy effective field theories of nuclear physics, promise to provide reliable determinations of nuclear and hypernuclear few-body interactions to supplement experiments such as the facility for rare isotope beams (FRIB) in the U.S., and to refine studies of extreme astrophysical environment. This program will also constrain hadronic contributions to Standard Model and beyond-the-Standard Model processes, removes some of the long-standing uncertainties in reactions such as those occurring in Sun, the cross section of dark-matter candidates scattering off nuclei in experiments, and the rate of exotic processes such as the neutrinoless double-beta decay.

Sign Problems

Most interesting problems in field theory/many-body physics are too complex to allow for analytic solutions. A lot of what we know about these systems has been found through the use of the Monte Carlo method. A large class of problems, some related to the big open problems in Physics (dense nuclear matter in neutron stars, high Tc superconductivity, non-equilibrium dynamics, …), is not apporachable using current Monte Carlo techniques. In the last few years we have pushed a novel approach to solve these problems combining stochastic methods, multidimensional complex analysis, topology, machine learning, and more to attack these problems.

Dense Quark Matter

Neutron stars are superdense, compact astrophysical objects, one of the possible ends of stellar evolution. Their bulk is made of compressed neutrons and their physics is dominated by nuclear forces. It’s inside them that we find the densest matter in the Universe, the largest magnetic fields, the largest gravitational fields and, therefore, they are place where all sorts of unusual Physics happens. We use a combination of effective field theories, models and observations, from X-rays to gravity waves, to learn about them.

Quantum Simulations

The future construction of quantum computers — machines that exploit the unusual features of quantum mechanics to achieve calculations too hard for classical computers — challenges us to come up with quantum algorithms to solve probelms of interest to physicists. In particular, the simulation of field theories is a topic largely unexplored. We work on a variety of topics related to the use of quantum computers to study field theoretical/many-body problems.

Large-NC QCD

QCD is the theory of the strong force, and is characterized by an SU(3) (gauge) symmetry. The theory can be generalized to any group SU(N), and in the limit of large N, simplifies in several important respects, allowing qualitative (and occasionally quantitative) insights into the SU(3) theory of the real world.