We study the relation between Lévy processes under nonlinear expectations, nonlinear semigroups and fully nonlinear PDEs. First, we establish a one-to-one relation between nonlinear Lévy processes and nonlinear Markovian convolution semigroups. Second, we provide a condition on a family of...

We argue that the fiscal multiplier of government purchases is increasing in the spending shock, in contrast to what is assumed in most of the literature. The fiscal multiplier is largest for large positive government spending shocks and smallest for large contractions in government spending. We...

In this paper we construct the smallest semigroup S that dominates a given family of linear Feller semigroups. The semigroup S will be referred to as the semigroup envelope or Nisio semigroup. In a second step we investigate strong continuity properties of the semigroup envelope and show that it...

We investigate whether the macroeconomic effects of government spending shocks vary with the level of uncertainty. Using postwar US data and a Self-Exciting Interacted VAR (SEIVAR) model, we find that fiscal spending has positive output effects in tranquil times but is contractionary during...

Im Zentrum dieser Dissertation steht das Beschreiben und Erklären von Konjunkturdynamiken. Motiviert durch den außerordentlich starken wirtschaftlichen Einbruch in 2008/2009 betont die Arbeit dabei die Wichtigkeit der Nutzung von nichtlinearen Modellansätzen. Die Dissertation kann als Beitrag...