We introduce the concept of “negative bubbles” as the mirror image of standard financial bubbles, in which positive feedback mechanisms may lead to transient accelerating price falls. To model these negative bubbles, we adapt the Johansen-Ledoit-Sornette (JLS) model of rational expectation...

We analyze the impact of funding costs and margin requirements on prices of index options traded on the CBOE. We propose a model that gives upper and lower bounds for option prices in the absence of arbitrage in an incomplete market with differential borrowing and lending rates. We show that...

Ending the dependence on rating agencies is a top priority for the Financial Stability Board, which coordinates the G20 financial policies. Rating agencies have been accused of contributing to the recent financial crisis by misjudging the creditworthiness of mortgage-backed securities. Their...

We present an extension of the Johansen-Ledoit-Sornette (JLS) model to include an additional pricing factor called the Zipf factorʺ, which describes the diversification risk of the stock market portfolio. Keeping all the dynamical characteristics of a bubble described in the JLS model, the new...

The Johansen-Ledoit-Sornette (JLS) model of rational expectation bubbles with finite-time singular crash hazard rates has been developed to describe the dynamics of financial bubbles and crashes. It has been applied successfully to a large variety of financial bubbles in many different markets....

We analyze American put options in a hyper-exponential jump-diffusion model. Our contribution is threefold. Firstly, by following a maturity randomization approach, we solve the partial integro-differential equation and obtain a tight lower bound for the American option price. Secondly, our...

In the build-up to and especially in the weeks after the Russian invasion of Ukraine, stocks strongly exposed to the regulatory risks of the transition to a low-carbon economy did well, suggesting an expected slow-down of that transition. Analysts increased their earnings estimates for these...