2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/36289Gravitational-wave data analysis requires a detailed understanding of the highly relativistic, late stages of inspiral of neutron-star and black-hole binaries. A promising method to compute the late inspiral and its emitted waves is numerical relativity in co-rotating coordinates. The coordinates must be kept co-rotating via an appropriate choice of numerical relativity's lapse and shift functions. This article proposes a model problem for testing the ability of various lapse and shift prescriptions to keep the coordinates co-rotating.4 pages; submitted to Physical Review D15 as a regular articleGeneral Relativity and Quantum Cosmologytext