Han Dynasty network analysis detects fragmentation 50 years before 220 CE partition via persistent homology

{"Three networks were built from CHGIS v6 prefecture data and least-cost paths on a 1 km DEM: H_adm (392 nodes ending at formal dissolution), H_geo (nodes persisting beyond administrative end-dates), and an 81-node Silk Road trade control. Persistent homology tracked β0 and β1 features across time slices, yielding a collapse threshold H* = 0.5241 identical to the Roman-Byzantine case. Wasserstein distance between admin and geo networks jumped from 0 to 737 at 190 CE, one decade after the Yellow Turban Rebellion.","The divergence signature—admin collapse paired with geo expansion—reveals internal fragmentation rather than external conquest, a pattern missed by dynastic histories focused on court politics. Early-warning metrics (Wasserstein velocity, correlation length ξ, Integrated Change Tracker) all crossed thresholds 45–50 years prior to formal partition, matching the 184 CE onset of widespread rebellion. This topological precursor generalizes the Roman result and directly links administrative dissolution to territorial reorganization observable in modern state networks.","Traditional historiography underweights the structural resilience of geographic connectivity after administrative failure; the Han data show that trade and terrain networks can sustain β1 cycles for decades, seeding successor polities. Applying the same pipeline to contemporary supply-chain or administrative graphs could flag analogous early-warning signals in federal systems facing regional autonomy movements.","The principal limitation remains dependence on CHGIS dating precision and the five friction channels chosen for edge costs; higher-resolution archaeological layers and alternative cost functions would tighten confidence intervals on the 45-year lead time."}