2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/112025We investigate the viscosity driven instability in rotating relativistic stars by means of an iterative approach. We focus on polytropic rotating equilibrium stars and impose an m=2 perturbationin the lapse. We vary both the stiffness of the equation of state and the compactness of the star to study those effects on the value of the threshold. For a uniformly rotating star, the criterion T/W, where T is the rotational kinetic energy and W is the gravitational binding energy, mainly depends on the compactness of the star and takes values around 0.13 ~ 0.16, which differ slightly from that of Newtonian incompressible stars (~ 0.14). For differentially rotating stars, the critical value of T/W is found to span the range 0.17 - 0.25. This is significantly larger than the uniformly rotating case with the same compactness of the star. Finally we discuss a possibility of detecting gravitational waves from viscosity driven instability with ground-based interferometers.v1: 14 pages with 10 figures, revtex4.cls. Submitted to Physical Review D; v2: Minor correction to the central enthalpy and typos, 13 pages with 10 figures, revtex4.cls. Physical Review D (2006) in press; v3: Published version, 13 pages with 10 figures, revtex4.cls. Physical Review D (2006) 084006AstrophysicsGeneral Relativity and Quantum Cosmologytext