Kang-Sin Choi - Quarks and Leptons From Orbifolded Superstring: 954 (Lecture Notes in Physics)

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One-and-a-half decades after the first edition, a lot of progress has been made in the application of string compactification. More realistic models have been built, more unified aspects of string theory have been understood, and more mathematical tools have become available. We now understand better the position of the orbifolded string theories in the moduli space and their connections to other constructions. Previously known symmetries are rederived from stringy and geometric effects. The landscape scenario has been heavily used in understanding the smallness of the cosmological constant.

To meet the recent development, we completely rewrote Chaps.. We have also tried to make the whole book more coherent and the exposition clearer.

This book was originally designed to be a toolkit on the compactification of the heterotic string. So, we provide more ready-made formulae. We hope that this revision helps everyone to more deeply understand the unified aspects of string theory and practically build more realistic models.

We are grateful to Stefan Groot Nibbelink, Hirotaka Hayashi, Tatsuo Kobayashi, Bumseok Kyae, Seung-Joo Lee, Hans-Peter Nilles, Felix Plger, Stuart Raby, Sul Ramos-Snchez, Michael Ratz, Soo-Jong Rey, Patrick K. S. Vaudrevange, Akin Wingerter and Piljin Yi, for helping us learn and clarify ideas.

Using the successful standard model of particle physics but without clear guidance beyond it, it is a difficult task to write a physics book beyond the standard model from a phenomenological point of view. At present, there is no major convincing inner-space-related experimental evidence against the standard model. The neutrino oscillation phenomena can be considered part of it by including a singlet field in the spectrum. Only the outer-space observations on matter asymmetry, dark matter, and dark energy hint at the phenomenological need for an extension, yet the theoretical need has been with us for almost three decades, chiefly because of the gauge hierarchy problem in the standard model.

Thus, it seems that going beyond the standard model hinges on the desirability of resolving the hierarchy problem. At the field theory level, it is fair to say that the hierarchy problem is not as desperate as the nonrenormalizability problem present in the old VA theory of weak interactions on the road to the standard model. An extension beyond the standard model can easily be ruled out as witnessed in the case of technicolor. However, a consistent framework with supersymmetry for a resolution of the hierarchy problem has been around for a long time. Even its culprit superstring has been around for 20 years, and the most remarkable thing about this supersymmetric extension is that it is still alive. So, the time is ripe for phenomenologists to become acquainted with superstring and its contribution toward the minimal supersymmetric standard model in four spacetime dimensions.