Kurt Gottfried

Mozart and Quantum Mechanics: An Appreciation of Victor Weisskopf

Weisskopf had a rare and harmonious blend of sentiment and intellectual rigor. He liked to say that his favorite occupations were Mozart and quantum mechanics.

Inferring the statistical interpretation of quantum mechanics from the classical limit

It is widely believed that the statistical interpretation of quantum mechanics cannot be inferred from the Schrödinger equation itself, and must be stated as an additional independent axiom. Here I propose that the situation is not so stark. For systems that have both continuous and discrete degrees of freedom (such as coordinates and spin respectively), the statistical interpretation for the discrete variables is implied by requiring that the systems gross motion can be classically described under circumstances specified by the Schrödinger equation. However, this is not a full-fledged derivation of the statistical interpretation because it does not apply to the continuous variables of classical mechanics.

Two-particle interference

The superposition principle leads to coherence phenomena that have no counterpart in classical optics. A gedanken experiment, due to Horne and Zeilinger, provides an especially clear illustration of such phenomena, and is presented in a manner suitable to an introductory quantum mechanics course. The experiment displays an interference pattern in the correlation between two particles produced in a momentum-conserving decay, but no interference pattern when either particle is observed separately; it also has interesting Einstein–Podolsky–Rosen-type correlations.

The Formal Framework

The concepts described impressionistically in chapter 1 must be cast into a well-defined mathematical formalism if one is to do theoretical physics. This chapter is devoted to a first cut at this task. Much of the material, such as that on symmetries and on the interpretation of quantum mechanics, will be reconsidered in greater depth in later chapters.

Moral calculus and the bomb

Targeting civilians, not using atomic weapons, was the moral watershed.

Selected Works of Hans A. Bethe: With Commentary

Energy level splitting in crystals the electron affinity of hydrogen stopping power of matter for fast electric particles eigenvalues and eigenfunctions of a linear chain of atoms on the quantum theory of the temperature of absolute zero the neutrino quantum theory of the diplon the scattering of neutrons by protons statistical theory of superlattices masses of light atoms maximum energy obtainable from the cyclotron approach to equilibrium in shock waves formation of deuterons by proton combination energy production in stars the electromagnetic shift of energy levels theory of the effective range in nuclear scattering nuclear many-body problem effect of a repulsive core in the theory of complex nuclei neutron star matter neutron star models with realistic high-density equations of state equations of state in the gravitational collapse of stars equation of state of a very hot gas of electrons and neutrinos the supernova shock and other papers.

Matter all in the mind.

Paul Diracs prediction of antimatter stands alone in being motivated solely by faith in pure theory, without any hint whatever from data.

P. A. M. Dirac and the discovery of quantum mechanics

Dirac’s contributions to the discovery of nonrelativistic quantum mechanics and quantum electrodynamics, prior to his discovery of the relativistic wave equation, are described.

Two-Electron Atoms

It is not possible to find exact eigenstates for the helium atom by analytical techniques. This is to be expected, because the classical counterpart, two satellites moving in each other’s gravitational field and that of a massive star, is already a problem that cannot be solved analytically. But very good and rather simple approximations give a good rendition of the helium spectrum, and reveal a profound consequence of the identity of the two electrons.

Sowing nuclear misconceptions

In its recent deliberations over the Comprehensive Test Ban Treaty, the US Senate was not well served by the directors of the US weapons laboratories.