Signals of merging supermassive primordial black holes in pulsar timing arrays

In this work we evaluate whether the gravitational wave background recently observed by a number of different pulsar timing arrays could be due to merging primordial supermassive black hole binaries. We find that for homogeneously distributed primordial black holes this possibility is inconsistent with strong cosmological and astrophysical constraints on their total abundance. If the distribution exhibits some clustering, however, the merger rate will, in general, be enhanced, opening the window for a consistent interpretation of the pulsar timing array data in terms of merging primordial black holes, if $\mu$-distortion constraints associated with the formation mechanism can be evaded.