## Universitätspublikationen

### Refine

#### Year of publication

#### Document Type

- Working Paper (1092) (remove)

#### Language

- English (1092) (remove)

#### Keywords

- Lambda-Kalkül (18)
- Deutschland (17)
- Venture Capital (16)
- monetary policy (14)
- Monetary Policy (12)
- Germany (11)
- Bank (10)
- Schätzung (10)
- monetary policy (10)
- Contagion (8)

#### Institute

- Center for Financial Studies (CFS) (525)
- Wirtschaftswissenschaften (373)
- Informatik (98)
- House of Finance (HoF) (89)
- Rechtswissenschaft (70)
- Sustainable Architecture for Finance in Europe (SAFE) (56)
- Institute for Monetary and Financial Stability (IMFS) (55)
- Exzellenzcluster Die Herausbildung normativer Ordnungen (14)
- Institut für sozial-ökologische Forschung (ISOE) (13)
- Kulturwissenschaften (11)

- Why did abolishing fees not increase public school enrollment in Kenya? (2011)
- A large empirical literature has shown that user fees signicantly deter public service utilization in developing #countries. While most of these results reflect partial equilibrium analysis, we find that the nationwide abolition of public school fees in Kenya in 2003 led to no increase in net public enrollment rates, but rather a dramatic shift toward private schooling. Results suggest this divergence between partial- and general-equilibrium effects is partially explained by social interactions: the entry of poorer pupils into free education contributed to the exit of their more affluent peers.

- The high return to private schooling in a low-income country (2011)
- Existing studies from the United States, Latin America, and Asia provide scant evidence that private schools dramatically improve academic performance relative to public schools. Using data from Kenya—a poor country with weak public institutions—we find a large effect of private schooling on test scores, equivalent to one full standard deviation. This finding is robust to endogenous sorting of more able pupils into private schools. The magnitude of the effect dwarfs the impact of any rigorously tested intervention to raise performance within public schools. Furthermore, nearly twothirds of private schools operate at lower cost than the median government school.

- The cost of firms’ debt financing (2013)
- We provide an assessment of the determinants of the risk remia paid by non-financial corporations on long-term bonds. By looking at 5,500 issues over the period 2005-2012, we find that in recent years the sovereign debt market turbulence has been a major driver of corporate risk. Compared with the three-year period 2005-07 before the global financial crisis, in the years 2010-12 Italian, Spanish and Portuguese firms paid on average between 70 and 120 basis points of additional premium due to the negative spillovers from the sovereign debt crisis, while German firms got a discount of 40 basis points.

- The capital structure of banks and practice of bank restructuring : eight case studies on current bank restructurings in Europe ; final report (2013)
- This study presents an empirical analysis of capital and liability management in eight cases of bank restructurings and resolutions from eight different European countries. It can be read as a companion piece to an earlier study by the author covering the specific bank restructuring programs of Greece, Spain and Cyprus during 2012/13. The study portrays for each case the timelines between the initial credit event and the (last) restructuring. It proceeds to discuss the capital and liability management activity before restructuring and the restructuring itself, launches an attempt to calibrate the extent of creditor participation as well as expected loss by government, and engages in a counterfactual discussion of what could have been a least cost restructuring approach. Four of the eight cases are resolutions, i.e. the original bank is unwound (Anglo Irish Bank, Amagerbanken, Dexia, Laiki), while the four other banks have de-facto or de-jure become nationalized and are awaiting re-privatization after the restructuring (Deutsche Pfandbriefbank/Hypo Real Estate, Bankia, SNS Reaal, Alpha Bank). The case selection follows considerations of their model character for the European bank restructuring and resolution policy discussion while straddling both the U.S. (2007 - 2010) and the European (2010 - ) legs of the financial crisis, which each saw very different policy responses....

- VaR-implied tail-correlation matrices (2013)
- Empirical evidence suggests that asset returns correlate more strongly in bear markets than conventional correlation estimates imply. We propose a method for determining complete tail correlation matrices based on Value-at-Risk (VaR) estimates. We demonstrate how to obtain more efficient tail-correlation estimates by use of overidentification strategies and how to guarantee positive semidefiniteness, a property required for valid risk aggregation and Markowitz{type portfolio optimization. An empirical application to a 30-asset universe illustrates the practical applicability and relevance of the approach in portfolio management.

- Energy-based model of forming subgroups on finite metric space (2009)
- Local interactions between particles of a collection causes all particles to reorganize in new positions. The purpose of this paper is to construct an energy-based model of self-organizing subgroups, which describes the behavior of singular local moves of a particle. The present paper extends the Hegselmann-Krause model on consensus dynamics, where agents simultaneously move to the barycenter of all agents in an epsilon neighborhood. The Energy-based model presented here is analyzed and simulated on finite metric space. AMS Subject Classifications:81T80; 93A30; 37M05; 68U20

- Descriptional complexity of cellular automata and decidability questions (2001)
- We study the descriptional complexity of cellular automata (CA), a parallel model of computation. We show that between one of the simplest cellular models, the realtime-OCA. and "classical" models like deterministic finite automata (DFA) or pushdown automata (PDA), there will be savings concerning the size of description not bounded by any recursive function, a so-called nonrecursive trade-off. Furthermore, nonrecursive trade-offs are shown between some restricted classes of cellular automata. The set of valid computations of a Turing machine can be recognized by a realtime-OCA. This implies that many decidability questions are not even semi decidable for cellular automata. There is no pumping lemma and no minimization algorithm for cellular automata.

- Minimizing finite automata is computationally hard (2002)
- It is known that deterministic finite automata (DFAs) can be algorithmically minimized, i.e., a DFA M can be converted to an equivalent DFA M' which has a minimal number of states. The minimization can be done efficiently [6]. On the other hand, it is known that unambiguous finite automata (UFAs) and nondeterministic finite automata (NFAs) can be algorithmically minimized too, but their minimization problems turn out to be NP-complete and PSPACE-complete [8]. In this paper, the time complexity of the minimization problem for two restricted types of finite automata is investigated. These automata are nearly deterministic, since they only allow a small amount of non determinism to be used. On the one hand, NFAs with a fixed finite branching are studied, i.e., the number of nondeterministic moves within every accepting computation is bounded by a fixed finite number. On the other hand, finite automata are investigated which are essentially deterministic except that there is a fixed number of different initial states which can be chosen nondeterministically. The main result is that the minimization problems for these models are computationally hard, namely NP-complete. Hence, even the slightest extension of the deterministic model towards a nondeterministic one, e.g., allowing at most one nondeterministic move in every accepting computation or allowing two initial states instead of one, results in computationally intractable minimization problems.

- On one-way cellular automata with a fixed number of cells (2003)
- We investigate a restricted one-way cellular automaton (OCA) model where the number of cells is bounded by a constant number k, so-called kC-OCAs. In contrast to the general model, the generative capacity of the restricted model is reduced to the set of regular languages. A kC-OCA can be algorithmically converted to a deterministic finite automaton (DFA). The blow-up in the number of states is bounded by a polynomial of degree k. We can exhibit a family of unary languages which shows that this upper bound is tight in order of magnitude. We then study upper and lower bounds for the trade-off when converting DFAs to kC-OCAs. We show that there are regular languages where the use of kC-OCAs cannot reduce the number of states when compared to DFAs. We then investigate trade-offs between kC-OCAs with different numbers of cells and finally treat the problem of minimizing a given kC-OCA.

- On the descriptional complexity of iterative arrays (2003)
- The descriptional complexity of iterative arrays (lAs) is studied. Iterative arrays are a parallel computational model with a sequential processing of the input. It is shown that lAs when compared to deterministic finite automata or pushdown automata may provide savings in size which are not bounded by any recursive function, so-called non-recursive trade-offs. Additional non-recursive trade-offs are proven to exist between lAs working in linear time and lAs working in real time. Furthermore, the descriptional complexity of lAs is compared with cellular automata (CAs) and non-recursive trade-offs are proven between two restricted classes. Finally, it is shown that many decidability questions for lAs are undecidable and not semidecidable.