The Odd Quantum

SAM TREIMAN
Pages: 280
https://www.jstor.org/stable/j.ctt7s5qj

1. Front Matter
(pp. i-iv)
(pp. v-vi)
3. PREFACE
(pp. vii-2)
4. Introduction
(pp. 3-26)

In the physics section of the University of Chicago catalog for 1898–99, one reads the following:

While it is never safe to affirm that the future of the Physical Sciences has no marvels in store even more astonishing than those of the past, it seems probable that most of the grand underlying principles have been firmly established and that further advances are to be sought chiefly in the rigorous application of these principles to all the phenomena which come under our notice. . . . An eminent physicist has remarked that the future truths of Physical Science are to...

5. CHAPTER TWO Classical Background
(pp. 27-60)

Quantum mechanics may run against the grain of ordinary experience, but the Newtonian mechanics that it supplanted also took some getting used to by our ancestors (and still does, for many contemporaries). Probably the two most widely quoted mantras taken from physics are Einstein’sE=mc² and Newton’s

$$\rm{\bf{F}}=\it{m}\rm{\bf{a}}.\caption{(2.1)}$$

In this chapter, we will be looking at the world from a pre-quantum perspective; and to begin with, a nonrelativistic one as well. Newton’s equation governs the motion of an object of massmacted on by an external force F. The concept of mass we can leave unanalyzed for...

6. CHAPTER THREE The “Old” Quantum Mechanics
(pp. 61-79)

Electromagnetic interactions between charged particles propagate at a large but finite speed, the speed of light. Jiggle a charge over there, a charge here won’t react, won’t feel a force change, until the pulse reaches it. This is what gives such prominence and reality to the electric and magnetic field concepts, even though from the point of view of forces between material particles the fields may seem to be mere middlemen: charge produces field, field exerts force on another charge. Maxwell’s equations are expressed in terms of these middlemen. There are infinitely many different solutions of Maxwell’s equations. For example,...

7. CHAPTER FOUR Foundations
(pp. 80-118)

The birth of the modern quantum theory was surveyed in Chapter 1. The pace, not just of Chapter 1 but of the events described there, was quite breathless. The foundations of quantum mechanics were pretty well laid down by 1928. Indeed, in 1926, not long after Schroedinger’s first paper was published, Max Born provided the beginnings of a physical interpretation of what was going on. He presented his ideas rather casually, in a publication devoted mainly to other matters; but what he proposed represented nothing less than a revolution in our view of the world.

To get started, let us...

8. CHAPTER FIVE Some Quantum Classics
(pp. 119-148)

The title of this chapter indicates that we will be paying brief calls on a number of relatively simple problems that either are important in their own right or serve well to illustrate the workings of quantum theory. In all cases in this chapter we will be concerned with a single, nonrelativistic particle of massm.

Suppose that the particle is not acted upon by any force at all. In that case, the potentialVis a constant and we can take it to be zero. Since the energy is purely kinetic and therefore proportional to the square of the...

9. CHAPTER SIX Identical Particles
(pp. 149-172)

Although some of the principles of quantum mechanics were laid out earlier in general terms, for the most part we have concentrated so far on the case of a single particle. As the number of particles in a quantum system increases, the computational complications inevitably increase–often beyond reach if one is hoping for exact answers. Models based on physical insight and reasonable mathematical approximations have to intervene. However, as long as the particles in a system are all different one from another no new principles peculiar to multiparticle systems come into play. But, remarkably, the various elementary particles of...

10. CHAPTER SEVEN What’s Going On?
(pp. 173-190)

Quantum mechanics deals with probabilities. Observers deal with facts: meter readings, tracks in a photographic emulsion, clicks of a Geiger counter, and so on. The big question is, how do probabilities get converted into facts? The formulaic answer is that this conversion takes place whenever a measurement is performed on the quantum system under consideration. Operationally, as far as we know, that is the right answer; but it is very puzzling. The measuring apparatus on this view is regarded as lying outside the probabilistic structure of quantum mechanics. When called upon, it steps in and makes a definite selection from...

11. CHAPTER EIGHT The Building Blocks
(pp. 191-230)

We have mainly focused so far on the application of quantum principles to systems of immutable, nonrelativistic particles. In that framework, the various kinds of particles that occur in nature, as well as the force laws that describe their interactions, have to be accepted as inputs. In the case of electromagnetism and gravity, those force laws of course have a classical heritage. Nevertheless, in the nonrelativistic quantum context they entered from the outside. There is no inconsistency in any of this, but there are problems and limitations when one seeks to extend the framework. For one thing, it is not...

12. CHAPTER NINE Quantum Fields
(pp. 231-254)

The subnuclear particles that we are concerned with are tiny things that leave tracks in detectors of various sorts, or trigger Geiger counters, or register themselves in other particle-like ways. If stable they have definite masses; if unstable, definite lifetimes and almost definite masses. A certain subset of them, electrons, protons, and neutrons, combine in large numbers and in various groupings to make up the material, macroscopic world of everyday life. Photons, taken together in large numbers, make up the everyday world of light (and radio waves and X-rays and so on). For all these reasons, at the microscopic level...