Your article on the Axion Dark Matter eXperiment (ADMX) suggests that the lattice quantum chromodynamics (QCD) calculation by S. Borsanyi et al. (Nature 539, 69–71; 2016) might be bad news for the ADMX because it could place the axion mass beyond the detector's reach (see Nature http://doi.org/bxf8; 2016). We find this inference misleading.

The axion is a very well-motivated hypothetical particle because it solves a puzzle in the standard model of elementary particles (the 'strong CP problem'; see J. E. Kim and G. Carosi Rev. Mod. Phys. 82, 557; 2010) and because a cold population of axions is naturally produced in the early Universe that may constitute dark matter today.

The properties of the axion depend for the most part on a single parameter that may be taken as the axion mass. Unfortunately, the mass is poorly constrained and might plausibly range from 10−6 to 103 microelectronvolts. Inconclusive theoretical arguments have been put forth in support of each part of that range.

The only way to find out the axion mass is through experimental observation. Axion dark-matter detection methods are emerging that, in principle, cover the whole mass range. Experiments that use the resonant cavity technique, such as ADMX, are capable of discovering axions today. They should be vigorously pursued. The aforementioned lattice QCD calculation does not change this fundamental picture.