This chapter begins the final section of the book, which presents both review and new results of original research on decoherence and measurement theory. In this chapter, it is shown that normal quantum mechanics can lead to irreversible behavior in an open system, in contrast to the expectation of the Poincaré theorem that predicts repeating, cyclical behavior for all closed systems. The quantum Boltzmann equation, which implies the famous H-theorem that underlies all statistical mechanics, is derived.

This chapter presents the surprising mathematical result that classical systems can indeed have entanglement. However, the degree to which they can be entangled is strictly limited, while quantum systems have no limit to their amount of entanglement.

This chapter surveys some of the ways in which the Copenhagen interpretation of quantum mechanics has led to a various views of the world with spiritual and moral implications; the perspective of this chapter is that most of these views are not demanded by the actual theory and experiments of quantum mechanics.

This chapter discusses some of the “super” properties of lasers, superfluids, and superconductors in the context of quantum field theory, including their innate property of spontaneous coherence, which can be seen as the opposite of decoherence.

As the final part of the nonmathematical discussion in this book, this chapter surveys how quantum mechanics plays an important role in existing technology such as the transistors used in computers and nuclear energy, as well as more cutting-edge technologies such as quantum computing, and the strange properties of lasers and superconductors.

This chapter introduces the formal second quantization method for fermions in quantum field theory, and the connection to second quantization of bosons is shown. The picture of fermions as rotations between two states is presented, which helps the reader to see where the Pauli exclusion rule comes from. Finally, Dirac’s original derivation of his equation for relativistic motion of fermions is given.

This chapter gives a brief but quantitative introduction to the method of Feynman diagrams in quantum field theory, sufficient for the reader to understand what these diagrams mean. The concept of “vacuum energy” is discussed in this context.

This chapter gives a quantitative introduction to decoherence theory, including density matrix formalism in the context of quantum field theory, and a survey of the quantum trajectories method. Finally, the mathematical structure for a new proposal for spontaneous collapse, introduced nonmathematically in Chapter 6, is given.

This chapter shows how particles arise naturally as an effect of waves, known as “resonance,” and that the particle concept, properly understood, is not somehow incompatible with the existence of waves. The definitions of “fermion” and “boson” fields, often associated with “matter” and “energy” particles, are introduced. The solidness of objects in our experience is a direct consequence of fermion wave properties.

This chapter surveys modern progress in physics on the topic of “decoherence,” the physical process by which irreversible behavior can occur in wave systems. A substantial part of the chapter discusses a proposal by the author of this book for a spontaneous collapse theory that is connected to decoherence.

This chapter introduces the formal “second quantization” method for bosons in quantum field theory. It is shown that phonons (sound particles) and photons (light particles) are simple extensions of the physics of a spring-like oscillator. The connection of boson states to classical waves is shown in a discussion of “coherent states.”

This chapter presents some basic calculations that show counterintuitive or unexpected results. First, it is shown that the Planck spectrum of light, which played an important role in the history of quantum mechanics, doesn’t say anything about the existence of indivisible particles. Second, a brief discussion of “chaos theory” shows that jumpy and unpredictable behavior can occur in classical systems. Last, the concept of “entanglement” is introduced as a basic property of quantum systems.

This chapter discusses what we mean by particle detectors and “quantum jumps.” Modern results are presented that show that particle detection is not instantaneous, and that the photoelectric effect does not prove the existence of particles; it is a purely wavelike effect. The Born rule for random clicks of measurements in detectors is introduced and discussed, and quantum “uncertainty” is introduced.