I also need the ELI25, however I think that the paper might be indicating that following the same procedure for spontaneous scalarization to vector fields may

I also need the ELI25, however I think that the paper might be indicating that following the same procedure for spontaneous scalarization to vector fields may yield unphysical results. That being said, I can't tell if the belief is that a ghost instability is inherently a mathematical object - or something that may be physical but we simply do not know. > Lastly, we stress that our results are relevant for most known extensions of spontaneous scalarization to other fields, not just the vectors, and our study can be considered as a first step to obtain a no-go theorem for extending spontaneous scalarization to other fields. For vector fields, Garcia-Saenz et al. [51] has identified the presence of ghost and gradient instabilities in the background of compact objects in a broad class of generalized Proca theories [84,85]. Similar concerns were also raised in the context of cosmology in Ref. [86]. Going beyond vector fields, all known formulations of nonminimally coupled spin-2 fields that could spontaneously grow are known to lead to ghost instabilities as well [75]. Likewise, p-form fields also have the same constraint structure we discussed in Sec. V, hence they suffer from similar divergent terms [87]. Spontaneous growth of spinor fields as it was introduced in Ref. [88] also contains divergent terms.