Green-Schwarz mechanism

John H. Schwarz said; "our work was universally ignored." Since string theory failed at first at describing the strong nuclear force, why should it succeed at an even grander goal (being a theory of quantum gravity)? There were even further conflicts between string theory and quantum mechanics that came about in the 1970s and 1980s. String theory at that point appeared to be just another attempt at bringing together quantum mechanics with gravity. 

This is, until 1984! Michael Green and John H. Schwarz showed that the conflicts between string theory and the quantum theory could be resolved. This paper was the result of more than a decade of intense research. String theory, at this point, was proposed to have the capacity to describe all four of the fundamental forces: gravity, electromagnetism and the strong and weak nuclear forces. This remarkable work by John H. Schwarz and Michael Green in 1984 led to string theory being center stage in high energy physics. 

Indeed, string theory, will be taken serious again in 1984, after another remarkable proposal by John. H. Schwarz and Michael Green. Indeed, the proposal that string theory could provide the resolution to this conundrum between general relativity and quantum mechanics came in 1984, to Michael Green and John H. Schwarz. This was the so-called “first superstring revolution”. String theory, at this point was shown to have the capacity to be able to describe all four of the fundamental interactions as well: gravity, electromagnetism and the strong and weak nuclear forces. It could also describe matter. 

This period of research actually started by work done by Edward Witten and Luis Alvarez Gaume, who proved a year earlier, in 1983, that quantum field theories, have gravitational anomalies. Their research led to the conclusion that type I string theories were not consistent theories of gravity. However, John H. Schwarz and Michael Green, are going to show that these anomalies cancel (or are avoided) in some particular versions of string theory. What they did was changed the gauge group to SO(32) in type I string theory, and the anomaly was avoided. The dimension of the gauge group had to be 496. This was a necessary condition for the superstring to make sense as a theory of everything. This kind of satisfactory theory of everything, must account the four fundamental interactions of nature. As we can see, mathematically, 4 dimensions, is not big enough to account for these forces. This is the demand for a powerful theory, such as string theory. The original Riemannian metric tensor of Einstein, however, can be raised to incorporate other forces, and hence, other dimensions. The physical laws depend on the geometry of these hidden, extra dimensions. The theme appears to be that the laws of physics become simpler in higher dimensions. Are the symmetries of the subatomic world, hidden in extra dimensional space?