I remember that when I first learned the Canonical Commutation Relations in quantum mechanics, they seemed mysterious: I knew I was supposed to view this as a law…
Spatial translations in quantum mechanics
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Pauli’s Theorem is not a theorem (not as Pauli stated it)
There is a quirk in the literature on time-energy uncertainty. It might have started as a little sloppiness. But it has grown into an error that seems to have spread…
What is a superselection rule?
A superselection rule is a special limitation on what is observable in the quantum world. For example, we can never seem to observe interference from the relative phases between a…
Philosophy and Physics in the Kadison-Singer Conjecture
A promising proof of the so-called Kadison-Singer conjecture was announced yesterday. Mathematicians are excited, because this conjecture is equivalent to a remarkable number of open problems in other fields. And…
Beyond the CPT theorem
Virtually all known laws of physics are invariant under the CPT transformation — that is, the combined operations of Charge conjugation (C), Parity or “mirror flipping” (P), and Time reversal…