Real-tree geometry for continuum random trees #
The deterministic core proves that complete four-point metric spaces with midpoints are real
trees. Continuous real functions code compact metric real trees through their interval minima;
the four-point and midpoint properties are proved for these quotients. The root is time zero,
and the probability mass is the Lebesgue pushforward. The map to rooted measured isometry
classes is 6-Lipschitz for the uniform norm. Finite plane trees are bundled with their vertex
graph metric, root and uniform probability on all vertices. First contour visits embed these
vertices isometrically in the contour-coded real tree, preserving the root. Deterministic
rerooting is a genuine measured isometry with the chosen new root. Uniform vertex mass is
compared with contour mass, and uniform contour convergence transfers deterministically to
rooted GHP under the explicit size/divisor assumptions, both deterministically and in law
on varying probability spaces with random sizes. A continuous Brownian bridge law is
constructed from the pinned Brownian supplier. Its minimum is strictly negative almost surely,
and the minima on [0,b] and [c,d] are almost surely unequal when b < c ≤ d < 1.
Hence the minimum is almost surely attained at a unique interior time, and the Vervaat
transform of the bridge is almost surely strictly positive on (0,1).
The deterministic Vervaat map is measurable. The identification of the Vervaat image with the
normalized Brownian excursion is proved in the stable layer
(BGW.StableTrees.BrownianIdentification.levyExcLaw_two). The uniform leaf measure of large
trees has the same rooted GHP limit in law as the uniform vertex measure.