  ALP-photon couplings are modeled in large ensembles of string vacua and
random matrix theories. In all cases, the effective coupling increases
polynomially in the number of ALPs, of which hundreds or thousands are expected
in the string ensembles, many of which are ultralight. The expected value of
the couplings $g_{a\gamma\gamma}\simeq 10^{-12}\text{GeV}^{-1} -
10^{-10}\text{GeV}^{-1}$ provide viable targets for future x-ray telescopes and
axion helioscopes, and in some cases are already in tension with existing data.
