In this paper, we consider a security market in which two investors on different information levels maximize their expected logarithmic utility from terminal wealth. While the ordinary investor's portfolio decisions are based on a public information flow, the insider possesses from the beginning...

In this paper we transfer martingale representation theorems from some given filtration to an initially enlarged filtration , where G is a random variable satisfying an equivalence assumption. We use then one of these theorems to solve the problem of maximizing the expected utility from both...

We consider a general stochastic model of frictionless continuous trading. The price process is a semimartingale and the model is incomplete. Our objective is to hedge contingent claims by using trading strategies with a small riskiness. To this end, we introduce a notion of local R-minimality...

Let L be a multidimensional Lévy process under P in its own filtration and consider all probability measures Q turning L into a local martingale. The minimal entropy martingale measure QE is the unique Q which minimizes the relative entropy with respect to P. We prove that L is still a Lévy...