Mathematics underlying the 2008 financial crisis, and a possible remedy
arxiv.org
arxiv.org
Second, there's a reason states don't print their own currency and the EU has adopted a common currency: it makes economic coordination so much more efficient. If each state had its own currency we would waste efficiency constantly exchanging currency, and out of state business would become subject to the volatile exchange fund market. Sure, this idea may solve one problem, but it certainly creates many more.