  Based on recent results obtained by the Pierre Auger Observatory (PAO), it
has been hypothesized that Centaurus A (Cen A) is a source of ultra-high-energy
cosmic rays (UHECRs) and associated neutrinos. We point out that the diffuse
neutrino flux may be used to constrain the source model if one assumes that the
ratio between the UHECR and neutrino fluxes outputted by Cen A is
representative for other sources. Under this assumption we investigate the
relation between the neutrino flux from Cen A and the diffuse neutrino flux.
Assuming furthermore that Cen A is the source of two UHECR events observed by
PAO, we estimate the all-sky diffuse neutrino flux to be ~200-5000 times larger
than the neutrino flux from Cen A. As a result, the diffuse neutrino fluxes
associated with some of the recently proposed models of UHECR-related neutrino
production in Cen A are above existing limits. Regardless of the underlying
source model, our results indicate that the detection of neutrinos from Cen A
without the accompanying diffuse flux would mean that Cen A is an exceptionally
efficient neutrino source.
