Theoretical particle physics develops models and mathematical tools to understand properties of elementary particles. Standard Model of particle physics, developed by 1970s, gives very accurate description of existing experiments involving electromagnetic, strong and weak interactions, but deviations from the Standard Model are expected at higher energies.
One of the major directions in particle theory is extraction of testable predictions from the Standard Model, which is especially challenging in the case of strong interaction. While nature of forces between quarks is known, direct computation of masses and decay rates of various particles requires better understanding of the theory at strong coupling, and significant progress in this direction has been happening over the last 30 years.
The second major theme in particle theory is development of ideas for physics which may lie beyond the Standard Model, such as supersymmetry, Grand Unification, or extra spatial dimensions. These models are formulated in the same framework, called quantum field theory, as the Standard Model itself, and by modifying its particle content and interactions, they cure some of the problems associated with Standard Model.
The third major direction in particle theory deals with quantization of gravitational interaction, i.e., with unifying quantum mechanics with general relativity. The framework of quantum field theory, which works successfully for other three interactions, breaks down in the case of gravity, so this force requires a new approach. String theory is the most promising framework for describing quantum gravity and for unifying it with other three interactions. While string theory cannot be directly tested in accelerators (the effects of quantum gravity are negligible at low energies), it resolves a number of paradoxes and gives important testable predictions in cosmology, e.g., in physics of the black holes and of the Big Bang. In addition to being the theory of quantum gravity, string theory provides valuable information about physics of strong interactions.
The research of the theory group at the University at Albany focuses on applications of string theory to physics of black holes and to strong interactions, more technical description can be found here.