  This review paper uses renormalization group techniques for signal detection
in nearly-continuous positive spectra. We highlight universal aspects of the
analogue field-theory approach. The first aim is to present an extended
self-consistent construction of the analogue effective field-theory framework
for data, which can be viewed as a maximum entropy model. In particular and
exploiting universality arguments, we justify the $\mathbb{Z}_2$-symmetry of
the classical action and we stress the existence of a large-scale (local)
regime and of a small-scale (nonlocal) regime. Secondly and related to noise
models, we observe the universal relation between phase transition and symmetry
breaking in the vicinity of the detection threshold. Finally, we discuss the
issue of defining the covariance matrix for tensorial-like data. Based on the
cutting graph prescription, we note the superiority of definitions based on
complete graphs of large size for data analysis.
