Quick question. Classically the harmonic oscillator Hamiltonian is often written 1 2 ( p 2 + q 2), while quantum mechanically it gets some extra ‘ground state energy’ making the Hamiltonian ...

Did you know that Lawvere did classified work on arms control in the 1960s, back when he was writing his thesis? You can read more here: Yes, that’s right. For technical reasons the n-Category Café ...

• a 2-rig over a field k is a Cauchy complete k -linear symmetric monoidal category is a line object if there’s an object y with x ⊗ y ≅ I. is a bosonic line object if it is a line object and the ...

I’d like to share here a personal project which might be of interest to the readers of this blog: the Clowder Project. Clowder is a wiki and reference work for category theory built using the same ...

July 2025's Entries The Duflo Isomorphism and the Harmonic Oscillator Hamiltonian Can the Duflo isomorphism explain the extra 1/2 in the Hamiltonian for the quantum harmonic oscillator? The Clowder ...

How do you count rooted planar n -ary trees with some number of leaves? For n = 2 this puzzle leads to the Catalan numbers. These are so fascinating that the combinatorist Richard Stanley wrote a ...