*P.J.E. Peebles*

- Published in print:
- 2019
- Published Online:
- May 2021
- ISBN:
- 9780691209821
- eISBN:
- 9780691206738
- Item type:
- chapter

- Publisher:
- Princeton University Press
- DOI:
- 10.23943/princeton/9780691209821.003.0003
- Subject:
- Physics, Particle Physics / Astrophysics / Cosmology

This chapter discusses abstract linear space of state vectors. The wave mechanics presented in the previous chapter is easily generalized for use in all the applications of quantum mechanics ...
More

This chapter discusses abstract linear space of state vectors. The wave mechanics presented in the previous chapter is easily generalized for use in all the applications of quantum mechanics explained in this book. In particular, to take account of spin, one just replaces the wave function with a set of functions, one for each possible choice of the quantum numbers of the z components of the spins of the particles. However, as the chapter shows, it is easy to adapt the wave mechanics formalism to the more general scheme that represents the states of a system as elements of an abstract linear space rather than a space of wave functions. This approach has the virtue that one can explicitly see the logic of the generalization of the wave function to take account of spin, and this is the road to other generalizations, like quantum field theory.Less

This chapter discusses abstract linear space of state vectors. The wave mechanics presented in the previous chapter is easily generalized for use in all the applications of quantum mechanics explained in this book. In particular, to take account of spin, one just replaces the wave function with a set of functions, one for each possible choice of the quantum numbers of the *z* components of the spins of the particles. However, as the chapter shows, it is easy to adapt the wave mechanics formalism to the more general scheme that represents the states of a system as elements of an abstract linear space rather than a space of wave functions. This approach has the virtue that one can explicitly see the logic of the generalization of the wave function to take account of spin, and this is the road to other generalizations, like quantum field theory.

*P.J.E. Peebles*

- Published in print:
- 2019
- Published Online:
- May 2021
- ISBN:
- 9780691209821
- eISBN:
- 9780691206738
- Item type:
- book

- Publisher:
- Princeton University Press
- DOI:
- 10.23943/princeton/9780691209821.001.0001
- Subject:
- Physics, Particle Physics / Astrophysics / Cosmology

This book explains the often counterintuitive physics of quantum mechanics, unlocking this key area of physics for students by enabling them to work through detailed applications of general concepts ...
More

This book explains the often counterintuitive physics of quantum mechanics, unlocking this key area of physics for students by enabling them to work through detailed applications of general concepts and ideas. The book states general principles first in terms of wave mechanics and then in the standard abstract linear space formalism. It offers a detailed discussion of measurement theory — an essential feature of quantum mechanics — and emphasizes the art of numerical estimates. Along the way, the book provides a wealth of physical examples together with numerous problems, some easy, some challenging, but all of them selected because they are physically interesting. The book is an essential resource for advanced undergraduates and beginning graduate students in physics.Less

This book explains the often counterintuitive physics of quantum mechanics, unlocking this key area of physics for students by enabling them to work through detailed applications of general concepts and ideas. The book states general principles first in terms of wave mechanics and then in the standard abstract linear space formalism. It offers a detailed discussion of measurement theory — an essential feature of quantum mechanics — and emphasizes the art of numerical estimates. Along the way, the book provides a wealth of physical examples together with numerous problems, some easy, some challenging, but all of them selected because they are physically interesting. The book is an essential resource for advanced undergraduates and beginning graduate students in physics.

*P.J.E. Peebles*

- Published in print:
- 2019
- Published Online:
- May 2021
- ISBN:
- 9780691209821
- eISBN:
- 9780691206738
- Item type:
- chapter

- Publisher:
- Princeton University Press
- DOI:
- 10.23943/princeton/9780691209821.003.0001
- Subject:
- Physics, Particle Physics / Astrophysics / Cosmology

This chapter presents the origins of quantum mechanics. The story of how people hit on the highly non-intuitive world picture of quantum mechanics, in which the physical state of a system is ...
More

This chapter presents the origins of quantum mechanics. The story of how people hit on the highly non-intuitive world picture of quantum mechanics, in which the physical state of a system is represented by an element in an abstract linear space and its observable properties by operators in the space, is fascinating and exceedingly complicated. The much greater change from the classical world picture of Newtonian mechanics and general relativity to the quantum world picture came in many steps taken by many people, often against the better judgment of participants. There are three major elements in the story. The first is the experimental evidence that the energy of an isolated system can only assume special discrete or quantized values. The second is the idea that the energy is proportional to the frequency of a wave function associated with the system. The third is the connection between the de Broglie relation and energy quantization through the mathematical result that a wave equation with fixed boundary conditions allows only discrete quantized values of the frequency of oscillation of the wave function (as in the fundamental and harmonics of the vibration of a violin string).Less

This chapter presents the origins of quantum mechanics. The story of how people hit on the highly non-intuitive world picture of quantum mechanics, in which the physical state of a system is represented by an element in an abstract linear space and its observable properties by operators in the space, is fascinating and exceedingly complicated. The much greater change from the classical world picture of Newtonian mechanics and general relativity to the quantum world picture came in many steps taken by many people, often against the better judgment of participants. There are three major elements in the story. The first is the experimental evidence that the energy of an isolated system can only assume special discrete or quantized values. The second is the idea that the energy is proportional to the frequency of a wave function associated with the system. The third is the connection between the de Broglie relation and energy quantization through the mathematical result that a wave equation with fixed boundary conditions allows only discrete quantized values of the frequency of oscillation of the wave function (as in the fundamental and harmonics of the vibration of a violin string).