Revisiting Higher-Spin Gyromagnetic Couplings

Understand

We analyze Bosonic, Heterotic, and Type II string theories compactified on a generic torus having constant moduli.

• By computing the hamiltonian giving the interaction between massive string excitations and $U(1)$ gauge fields arising from the graviton and Kalb-Ramond field upon compactification, we derive a general formula for such couplings that turns out to be universal in all these theories.
• We also confirm our result by explicitly evaluating the relevant string three-point amplitudes.
• From this expression, we determine the gyromagnetic ratio $g$ of massive string states coupled to both gauge-fields.