---
title: "Philipp Urban"
type: "entity"
entity_kind: "person"
status: "hub"
canonical_name: "Philipp Urban"
aliases: []
first_seen: "2026-07-29T00:00:00.000Z"
writer_model: "claude-sonnet-5"
connects_to: ["Gaussian curvature (color space)","CIELAB","CIEDE2000","isometric embedding","Deane B. Judd"]
---


Lead author of Urban, Rosen, Berns & Schleicher (2007), "Embedding non-Euclidean color spaces into Euclidean color spaces with minimal isometric disagreement" (*JOSA A* 24(6):1516–1528) — per corroborated-but-not-yet-quote-verified access, the paper that explicitly frames CIELAB-based color-difference formulas (CMC, CIE94, CIEDE2000) as having regions of nonzero Gaussian curvature obstructing isometric Euclidean embedding, roughly seventeen years before Ahrens et al. 2024 measures its own "Euclidization" work against the same framing. The paper's own text remains access-blocked to the vault as of 2026-07-28 (ResearchGate and direct-PDF routes both 403).

## References
- [[claim-urban-2007-nonzero-gaussian-curvature-isometric-embedding-obstruction-unverified]]