  We take a first step towards a holographic description of a black hole by
means of a flow equation. We consider a free theory of multiple scalar fields
at finite temperature and study its holographic geometry defined through a free
flow of the scalar fields. We find that the holographic metric has the
following properties: i) It is an asymptotic Anti-de Sitter (AdS) black brane
metric with some unknown matter contribution. ii) It has no coordinate
singularity and milder curvature singularity. iii) Its time component decays
exponentially at a certain AdS radial slice. We find that the matter spreads
all over the space, which we speculate to be due to thermal excitation of
infinitely many massless higher spin fields. We conjecture that the above three
are generic features of a black hole holographically realized by the flow
equation method.
