 Type II string theory

Type II superstring theory is a ten-dimensional closed oriented superstring theory with spacetime supersymmetry and no tachyon. Its massive closed-string levels have squared masses separated by $4/{\alpha }^{\prime }$.

Type II string theory is one of the five consistent superstring theories in theoretical physics. It is a framework that arises from the principles of string theory, which postulates that the fundamental constituents of the universe are not point-like particles but rather one-dimensional "strings" that can vibrate in different modes.