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We present a unified Boltzmann-transport theory for the drag resistivity in two-component systems close to a second-order phase transition. We find general expressions for the drag resistivity in two and three spatial dimensions, for arbitrary population and mass imbalance, for particle- and hole-like bands, and show how to incorporate, at the Gaussian level, the effect of fluctuations close to a phase transition. We find that the proximity to the phase transition enhances the drag resistivity upon approaching the critical temperature from above, and we qualitatively derive the temperature dependence of this enhancement for various cases. In addition, we present numerical results for two concrete experimental systems: i) three-dimensional cold atomic Fermi gases close to a Stoner transition and ii) two-dimensional spatially-separated electron and hole systems in semiconductor double quantum wells., Comment: 15 pages, 5 figures

We develop multivariate measures of synchronicity and co-movement of business cycles. In addition to synchronicity, the co-movement measure takes differences between cycle amplitudes into account that have been overlooked in most previous studies. We apply the new measures to the euro area. Synchronicity and co-movement for the region as a whole do not exhibit a clear upward tendency. Although several countries saw the similarity of their business cycle vis-`a-vis the euro area reference cycle increase, national business cycles remain fairly diverse. Changes in business cycle amplitudes cause most of the observed change in cycle co-movement.