Conclusion

I have touched on some of the highlights of the current revolution, but there is much more that does not fit here. For example, I have not discussed the dramatic discoveries of Seiberg and Witten for supersymmetric gauge theories and their extensions to string theory. Another important development due to Vafa (called F theory) has made it possible to construct large new classes of non-perturbative vacua of Type IIB superstrings. For a somewhat more techincal discussion of these recent developments I recommend (references to be included later).

Despite all the progress that has taken place in our understanding of superstring theory, there are many important questions whose answers are still unknown. It is not clear how many important discoveries still remain to be made before it will be possible to answer the ultimate question that we are striving towards -- why does the universe behave the way it does? Short of that, we have some other pretty big questions. What is the best way to formulate the theory? How and why is supersymmetry broken? Why is the cosmological constant, which characterizes the energy density of the vacuum, so small (or zero)? How is a realistic solution of the theory chosen from the myriad of possibilities? What are the cosmological implications of the theory? What testable predictions can we make? Stay tuned.


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