The First Superstring Revolution

In 1984-85 there was a series of discoveries[4] that convinced many theorists that superstring theory is a very promising approach to unification. Almost overnight, the subject was transformed from an intellectual backwater to one of the most active areas of theoretical physics, which it has remained ever since.
By the time the dust settled in 1985, it seemed clear that there are five different superstring theories, each requiring ten dimensions (nine space and one time), and that each of them has a consistent description in term of a power series expansion in the coupling constant (perturbation expansion).
The five theories, about which I'll say more later, are denoted type I, type IIA, type IIB, E8 X E8 heterotic (HE, for short), and SO(32) heterotic (HO, for short).
The type II theories have two supersymmetries in the ten-dimensional sense, while the other three have just one.
The type I theory is special in that it is based on unoriented open and closed strings, whereas the other four are based on oriented closed strings.
The IIA theory is special in that it is non-chiral (i.e., it is parity conserving), whereas the other four are chiral (parity violating).
At this point I'll end the historical discussion and turn to superstring theory itself.

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| Contents | Resolving Contradictions | Supersymmetry | A Brief History of Superstings |

| Basic Ideas of Superstring Theory | Superstring Revolution, part deux |