Breathing velocity and normalised density as functions of the azimuth. Upper panel: isolated model. The solid line and dashed line represent the breathing velocity and the normalised density, respectively, averaged over R between R = 8 kpc and 8.5 kpc. The arrow indicates the direction of the galaxy rotation. Lower panel: same as the upper panel but in the perturbed model. This plot quantifies the displacement in Fig. 14, showing that the breathing velocity minimum is shifted to the trailing side relative to the density peak in the perturbed model with tidally induced arms. This contrasts with the alignment seen in the isolated model with dynamic arms.