What is the Higgs boson? How are all forces unified in particle physics? What is a mechanism for gauge symmetry breaking? Are there extra dimensions in spacetime? The Higgs boson discovered in 2012 is a crucial piece in the standard model for unifying electromagnetic and weak forces. Gauge symmetry is spontaneously broken by the Higgs mechanism. There is an alternative scenario. In the Hosotani mechanism gauge symmetry is spontaneously broken by dynamics of gauge fields in the fifth dimension. The Higgs boson appears as a fluctuation mode of an Aharonov-Bohm phase in the fifth dimension. This leads to the scenario of gauge-Higgs unification. In this book gauge-Higgs unification is introduced from the basics and is applied to electroweak unification. It is seen that gauge-Higgs unification gives nearly the same phenomenology at low energies as the standard model, and leads to many predictions to be confirmed in future experiments. Request Inspection Copy Sample Chapter(s) Preface Chapter 1: Introduction Contents: Introduction Higgs Mechanism Aharonov-Bohm Effect and Hosotani Mechanism Quantum Effects and Hosotani Mechanism Gauge-Higgs Unification in Flat Space Randall-Sundrum Warped Space Gauge-Higgs Unification in the RS Space New Particles and Interactions Predictions Appendices: Natural Units, Dirac Matrices and SO(N) Effective Potential Bessel Functions Readership: Advanced undergraduate and graduate students, researchers and practitioners in the fields of particle physics and cosmology.