random-projection-orthogonal-beta-distribution
IN premise — summaries/2026/08/24/wiki-Random_projection.md
Created 2026-08-25T02:58:51+00:00
Orthogonal random projection of a unit vector yields ‖v‖² following a Beta(k/2, (d−k)/2) distribution with mean k/d.
Summary
When a unit-length vector is projected onto a random lower-dimensional subspace, the expected squared length of the result is exactly the fraction of dimensions kept (k out of d), and the full spread of possible outcomes follows a known Beta distribution. This gives the system a precise statistical benchmark for evaluating how much geometric structure random projections preserve or destroy, which underpins reasoning about dimensionality reduction and compressed representations.