2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/123020We introduce a novel model for DNA condensation (whip-toroid transition) using the path integral method in the framework of the non-linear sigma model on a line segment. We show that some of its classical configurations exhibit toroidal forms, and the system has phase transitions from a whip to toroidal phases with a parameter $c=W/(2l) (L/(2π))^2$. We also discuss stability and finite size effect on these states.RevTex4, 4 pages, 1 figure (colour), typo fixedSoft Condensed MatterBiomoleculestext