2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/125049We study small perturbations around the exactly marginal time-dependent string configuration of [1], and demonstrate the lack of the appropriate linearization. This implies that this configuration is an isolated fixed point of the $α^{'}$ flow in the pertinent space of theories.6 pages LaTeX, ammended version, includes modified discussion on linearisation about fixed point solution and arguments in favour of an `isolated fixed point'High Energy Physics - TheoryGeneral Relativity and Quantum CosmologyHigh Energy Physics - Phenomenologytext