Confinement and Dynamical Symmetry Breaking in non-SUSY Gauge Theory from S-duality in String Theory

We discuss an attempt to understand confinement and dynamical symmetry breaking in a 4-dimensional non-supersymmetric gauge theory using S-duality in type IIB string theory. The electric theory is a USp(2n) gauge theory and its magnetic dual is argued to be an SO(2n) or SO(2n-1) gauge theory. These theories are obtained as the low-energy effective theory of O3-D3bar systems in type IIB string theory, which are related by S-duality. Confinement and dynamical symmetry breaking in the USp(2n) gauge theory are caused by the condensation of scalar fields in the magnetic dual description, which is consistent with the scenario of the dual Meissner mechanism for the confinement.