Condensed matter physics deals with the physical properties of condensed phases of matter. The behaviors of a single or a few electrons, bosons, atoms, or spins can be described by quantum mechanics. The behavior of a few semi-classical atoms can act as a gas. Under suitable conditions, a large number of interacting electrons, bosons, atoms, or spins can show many emergent macroscopic phenomena not shared by only a few of them. Some of these types of emergent phenomena include superconductivity, superfluid, superradiances, quantum Hall effects, ferromagnetism, ferroelectricity, Mott insulators, quantum anti-ferromagnets, and nanocrystals. The MSU condensed matter theory group studies these emergent collective behaviors in various materials and cold atoms systems using both numerical and analytical approaches. The studies may be for equilibrium (such as specific heats, susceptibility or correlation functions) or non-equilibrium (such as photon radiations, nucleation or quantum decoherence). The studies involve both large-scale numerical simulations and analytical calculations.