Schwinging the Pendulum

Masses on springs get a lot of use in physics; you see them early in that first year of introductory classical mechanics with Hooke’s law and they come back over and over again after that. Physicists are fond of saying that basically everything in reality reduces to a mass on a spring if you squint […]

Angular momentum by harmonic oscillator

I’ve been thinking about Sakurai problem 3.19 for the past few days. The problem reads: 19.) What is the physical significance of the operators K+ ≡ a+†a-†        and       K- ≡ a+a- in Schwinger’s Scheme for angular momentum? Give nonvanishing matrix elements of K± I’m not sure I completely understand this problem yet. The ‘a’ operators […]