Repulsive renormalization-group trajectory

A repulsive renormalization-group trajectory leaves a renormalization-group fixed point along its unstable manifold as the coarse-graining length increases. Its tangent directions are relevant operators. The critical surface is instead the stable manifold, whose irrelevant coordinates approach the critical fixed point after relevant fields are tuned. For a discrete step, relevance is determined by multipliers larger than one in magnitude, not merely by their being positive.