In a financial system, the interconnectedness among entities from investing in common assets (portfolio overlaps) is considered an important channel for the propagation of systemic risk because this interconnectedness can facilitate the contagion of fire sales and lead to widespread sales as...

Building on the notion that bubbles are transient self-fulfilling prophecies created by positive feedback mechanisms, we construct the simplest continuous price process whose expected returns and volatility are functions of momentum only. The momentum itself is measured by a simple continuous...