The next hiding step on an EPR seed with arbitrary auxiliaries #
Stated in a bipartite model (Phase 4 of planning/mipco-track.md): the EPR seed beside an
arbitrary auxiliary state is the register model Ξ.reg (ι → F) of an arbitrary model Ξ, whose
players hold the matrices over ι → F with entries in Ξ's algebras, and an honest register
operator P, a complex matrix, acts as smulKron 1 P for either player. The honest operators are
symmetric, so the mirror identity of the register model (BipartiteModel.reg_mirror) makes each of
them an exact mirror of itself, and the step is hideCoarseOp_step_of_normalizer in the register
model. Register families are embedded, with their coarse-grainings and conditional ideals, by
fibSumIn_smulKron_one and conditionalIdeal_smulKron_one (ConditionalNormalizerStep.lean).
Exact ideal mirrors persist with any bipartite auxiliary model.
The next honest prefix commutes with the current coarse Hide measurement, both embedded in the matrices over any algebra.
The paired normalizer bound implies rigidity of the actual next coarse Hide measurement on the full seed/auxiliary carrier. All ideal mirrors and conditional product identities are supplied by the honest construction.