Grand Unified Theories

These course-tested lectures provide a technical introduction to Supersymmetric Grand Unified Theories (SUSY GUTs), as well as a personal view on the topic by one of the pioneers in the field. While the Standard Model of Particle Physics is incredibly successful in describing the known universe it is, nevertheless, an incomplete theory with many free parameters and open issues. An elegant solution to all of these quandaries is the proposed theory of SUSY GUTs. In a GUT, quarks and leptons are related in a simple way by the unifying symmetry and their electric charges are quantized, further the relative strength of the strong, weak and electromagnetic forces are predicted. SUSY GUTs additionally provide a framework for understanding particle masses and offer candidates for dark matter. Finally, with the extension of SUSY GUTs to string theory, a quantum-mechanically consistent unification of the four known forces (including gravity) is obtained. The book is organized in three sections: the first section contains a brief introduction to the Standard Model, supersymmetry and the Minimal Supersymmetric Standard Model. Then SUSY GUTs in four space-time dimensions are introduced and reviewed. In addition, the cosmological issues concerning SUSY GUTs are discussed. Then the requirements for embedding a 4D SUSY GUT into higher-dimensional theories including gravity (i.e. String Theory) are investigated. Accordingly, section two of the course is devoted to discussing the so-called Orbifold GUTs and how in turn they solve some of the technical problems of 4D SUSY GUTs. Orbifold GUTs introduce a new set of open issues, which are then resolved in the third section in which it is shown how to embed Orbifold GUTs into the E(8) x E(8) Heterotic String in 10 space-time dimensions.

Grand Unified Theories introduces the application of gauge field theories to a unified description of the strong, electromagnetic, weak, and gravitational interactions. The phenomenological aspects of the work are emphasized and explicit calculations presented. Many of the aspects of current research, including technicolor models, supersymmetry and supergravity, and the cosmological implications of these theories, are discussed in this book.This book is suitable for graduate students with a background in quantum mechanics, and experimental and theoretical particle physicists who want to understand the grand unified theories.

The Grand Unified Theory is the unification theory of the four fundamental forces of nature (gravity, electromagnetism, strong nuclear force, and weak nuclear force). It is through the interactions between these four forces of nature that everything in our universe is created, including our DNA and the cells that compose our body. Einstein spent much of the later part of his life trying to unify these forces, but without success. The grand unified theory is also called the theory of everything, because it is supposed to answer many fundamental questions about our universe. The questions such as, why does our universe exist? Why is our universe composed of three-dimensional space and not five or six? What is energy? Why is there conscious life in our universe? What is the function of life in the universal order?

The theoretical understanding of elementary particle interactions has under gone a revolutionary change during the past one and a half decades. The spontaneously broken gauge theories, which in the 1970s emerged as a prime candidate for the description of electro-weak (as weIl as strong) interactions, have been confirmed by the discovery of neutral weak currents as weIl as the w- and Z-bosons. We now have a field theory of electro-weak interactions at energy scales below 100 GeV-the Glashow-Weinberg-Salam theory. It is a renormalizable theory which enables us to do calculations without en countering unnecessary divergences. The burning question now is: Wh at lies ahead at the next level of unification? As we head into the era of supercolliders and ultrahigh energy machines to answer this question, many ap, pealing possi bilities exist: left-right symmetry, technicolor, compositeness, grand unifica ti on, supersymmetry, supergravity, Kaluza-Klein models, and most recently superstrings that even unify gravity along with other interactions. Experi ments will decide if any one or any combination of these is to be relevant in the description of physics at the higher energies. As an outcome of our con fidence in the possible scenerios for elementary particle physics, we have seen our understanding of the early uni verse improve significantly.

Paul Adrian Maurice Dirac, one of the greatest physicists of the twentieth century, died in 1984. His college, St John's College, Cambridge, generously endowed annual lectures to be held at Cambridge University in his memory. This 1990 volume includes an expanded version of the third Dirac Memorial Lecture presented by Abdus Salam.

General theorem providing a mathematical basis for a grand Unified Field Theory (GUT) is presented. The proof of the theorem is shown to be a recent work entitled 'Generalised Mathematical Proof of Einstein's Theory Using a New Group Theory', which has been reviewed by the American Mathematical Society. This work provides generic solutions to the unified field, from which both the Newtonian and Einsteinian gravitational fields seem to be recoverable. Furthermore, the electromagnetic field seems to be recoverable also from these solutions. Since the investigation does not assume the existence of particles a priori, matter could therefore be interpreted as high field intensity. Therefore, nuclear force fields (strong and weak) seem to be included. The solution seems to mathematically represent the modification of space-time predicted by Einstein's general relativity theory.

Why did Einstein tirelessly study unified field theory for more than thirty years? In this book, the author argues that Einstein believed he could find a unified theory of all of nature's forces by repeating the methods he thought he had used when he formulated general relativity. The book discusses Einstein's route to the general theory of relativity, focusing on the philosophical lessons that he learnt. It then addresses his quest for a unified theory for electromagnetism and gravity, discussing in detail his efforts with Kaluza-Klein and, surprisingly, the theory of spinors. From these perspectives, Einstein's critical stance towards the quantum theory comes to stand in a new light. This book will be of interest to physicists, historians and philosophers of science.

The past decade has witnessed dramatic developments in the field of theoretical physics. This book is a comprehensive introduction to these recent developments. It contains a review of the Standard Model, covering non-perturbative topics, and a discussion of grand unified theories and magnetic monopoles. It introduces the basics of supersymmetry and its phenomenology, and includes dynamics, dynamical supersymmetry breaking, and electric-magnetic duality. The book then covers general relativity and the big bang theory, and the basic issues in inflationary cosmologies before discussing the spectra of known string theories and the features of their interactions. The book also includes brief introductions to technicolor, large extra dimensions, and the Randall-Sundrum theory of warped spaces. This will be of great interest to graduates and researchers in the fields of particle theory, string theory, astrophysics and cosmology. The book contains several problems, and password protected solutions will be available to lecturers at www.cambridge.org/9780521858410.