The Theoretical Elementary Particle Physics group acknowledges that the fundamental task of physics is to learn the rules of the basic interactions governing the behavior of matter and to search for new laws when present knowledge fails to answer the remaining mysteries of the observable universe. At the foundation of modern theories of particle physics is a deep and beautiful symmetry principle: the invariance of physical laws under symmetry transformations at every space-time point. Theories that show this symmetry are known as Yang-Mills or Gauge Theories. The Standard Model of Strong, Electromagnetic and Weak interactions is the most successful of these theories. It describes all known interactions of matter except gravity.

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The Electroweak part of the Standard Model is being tested to a high degree of precision. The Strong interaction part, the Quantum Chromodynamics (QCD) Theory, which describes the interactions among the quarks, is being closely scrutinized, both perturbatively and nonperturbatively. The Standard Model is incomplete, however, since a number of fundamental puzzles, such as CP violation and the origin of masses, remain unsolved. The solutions to these problems probably lie outside the framework of the Standard Model. How does one solve the problem of masses? How does one solve QCD? These are among the topics under active investigation by UVa HEP theorists Hung and Thacker.

Arnold: Prof. Arnold studies the theory of the strong, weak, and electromagnetic interactions at extremely high, relativistic temperatures, such as in the very early Universe (less than a millionth of a second after the Big Bang) or in relativistic collisions in heavy ion accelerators. Topics he has studied include investigating why there is significantly more matter than anti-matter in the Universe and understanding the properties of quark-gluon plasmas. The theoretical methods used for these very high energy problems (as much as a quadrillion degrees Kelvin) can also be applied to certain ... More>

Hung:
Elementary particle physics has been crowned with spectacular successes in this last quarter of the past century. The cornerstone of such a success is the Standard Model of Elementary Particles which has been tested to a high level of precision. The Standard Model (SM), however, is incomplete. It cannot predict the number of "families". (Experimentally, one knows that there at least three families.) It cannot predict the electroweak mixing angle which is measured to a high level of accuracy. One does not know the origin of the masses of the constituents of matter: the quarks ... More>

Thacker: The study of elementary particles and their interactions has been refined and made precise by the development of the Standard Model, which describes all nongravitational interactions of all the known elementary particles in terms of the unifying principle of gauge invariance. The Standard Model is a gauge field theory, which can be viewed as a generalization of Quantum Electrodynamics. The study of the Standard Model, particularly the interactions of quarks and gluons, can be carried out using a combination of analytic methods and large scale computer calculations. Professor ... More>

Vaman: My research in theoretical particle physics is based on string theory, and I am especially interested in the connections between gauge and string theories. More>