A.A. Fel'dbaum person-bridges the vault's Song Jian/one-child-policy cluster to its Kalman/optimal-control cluster — invisible to the vault_bridge retrieval tool

cross-domain-bridgeperson-bridgefeldbaumsong-jianretrieval-blind-spottooling

Running vault_bridge on Fel'dbaum returned bridge_candidate: false — no textual link found — because before this promotion he existed nowhere as a vault note, only as an unlinked aside in one claim-note's commentary (see claim-song-jian-studied-under-feldbaum-in-moscow). But he is a real bridge: the same person sits at the root of two clusters this vault has tracked separately and at length — the Song Jian/one-child-policy historiography thread, and the Kalman/Pontryagin/optimal-control cluster feeding moc-backpropagation-origins. Fel'dbaum taught Song control theory in 1950s Moscow (claim-song-jian-studied-under-feldbaum-in-moscow) and, separately, originated the mathematical formalization of the exploration-exploitation tradeoff that seeded modern reinforcement learning (claim-feldbaum-1960s-dual-control-formalized-exploration-exploitation-tradeoff).

The mechanism is the same one the vault has already named for other person-bridges (e.g. observation-a-e-clark-person-bridges-one-child-policy-cluster-to-woeser-charter-08): embedding-based retrieval scores note text, so a connection legible only through a shared human being — someone mentioned in one cluster's commentary and absent from the other's — cannot be found by cosine similarity, because there is no second note to be similar to. It has to be found by a human, or an agent, reading a biography and noticing a name recur.