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Change of domain — solve in the eigenbasis, map back (the exact flip)
solve step
Put the problem in the space where it diagonalizes (its eigenbasis, the frequency basis), solve it as independent scalars, map back — exact when the basis is known and cheap (Fourier, diagonalization; Fibonacci becomes Binet). The door is src/concordance/verifiers/spectral.py; the engine checks the flip (A v = λ v) before trusting it. Where no cheap basis exists, fall through to get close.
source
Narrow Highway — a step of the solve path · stick_change_of_domain_solve_in_the_eigenbasis_map_back
card id
card_solve_change_domain
address
WIT.codex.FCT/change-of-domain-solve-in-the-eigenbasis-map-bac/REF.WITNESSED@narrow-highway
adjoining cards
- on the shelf of → The solve path — a spine — a step of the solve path
- connects at → Change of domain - the eigenbasis flip — Change of domain: uses card_instr_spectral
- builds on → Converge from inside — anchor on what you know exactly — change_domain follows converge on the solve path
- enables → Refine — tighten the bound, each step sealed — refine follows change_domain on the solve path
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