10,532 research outputs found
Schottky groups acting on homogeneous rational manifolds
We systematically study Schottky group actions on homogeneous rational
manifolds and find two new families besides those given by Nori's well-known
construction. This yields new examples of non-K\"ahler compact complex
manifolds having free fundamental groups. We then investigate their analytic
and geometric invariants such as the Kodaira and algebraic dimension, the
Picard group and the deformation theory, thus extending results due to
L\'arusson and to Seade and Verjovsky. As a byproduct, we see that the Schottky
construction allows to recover examples of equivariant compactifications of
SL(2,C)/\Gamma for \Gamma a discrete free loxodromic subgroup of SL(2,C),
previously obtained by A. Guillot.Comment: 30 pages; minor modifications, references have been added; to appear
in Journal f\"ur die reine und angewandte Mathematik (Crelle's Journal
Regulation and competition in German banking: an assessment
In Germany a public discussion on the "power of banks" has been going on for decades now with power having at least two meanings. On the one hand it is the power of banks to control public corporations through direct shareholdings or the exercise of proxy votes - this is the power of banks in corporate control. On the other hand it is market power - due to imperfect competition in markets for financial services - that banks exercise vis-à-vis their loan and deposit customers. In the past, bank regulation has often been blamed to undermine competition and the working of market forces in the financial industry for the sake of soundness and stability of financial services firms. This chapter tries to shed some light on the historical development and current state of bank regulation in Germany. In so doing it tries to embed the analysis of bank regulation into a more general industrial organisation framework. For every regulated industry, competition and regulation are deeply interrelated as most regulatory institutions - even if they do not explicitly address the competitiveness of the market - either affect market structure or conduct. This paper tries to uncover some of the specific relationships between monetary policy, government interference and bank regulation on the one hand and bank market structure and economic performance on the other. In so doing we hope to point to several areas for fruitful research in the future. While our focus is on Germany, some of the questions that we raise and some of our insights might also be applicable to banking systems elsewhere. Revised version forthcoming in "The German Financial System", edited by Jan P. Krahnen and Reinhard H. Schmidt, Oxford University Press
The Economic Effects of Restrictions on Government Budget Deficits: Imperfect Privte Credit Markets
We consider a pure-exchange overlapping-generations model We consider a pure-exchange overlapping-generations model with many consumers per generation and many goods per period. As in Ghiglino and Shell (2000), there is a government that collects taxes, distributes transfers and faces budget deficit restrictions. We introduce, for realism and symmetry with the government, imperfection in the private credit markets. We find that with constraints on individual credit and anonymous (i.e., non-personalized) lump-sum taxes, strong (or 'global') irrelevance of the government budget deficit is not possible, and weak irrelevance can hold only in very special situations. With credit constraints and anonymous consumption taxes, weak irrelevance holds provided the number of tax instruments is sufficiently large and at least one consumer's credit constraint is not binding.
A convex analysis approach to optimal controls with switching structure for partial differential equations
Optimal control problems involving hybrid binary-continuous control costs are
challenging due to their lack of convexity and weak lower semicontinuity.
Replacing such costs with their convex relaxation leads to a primal-dual
optimality system that allows an explicit pointwise characterization and whose
Moreau-Yosida regularization is amenable to a semismooth Newton method in
function space. This approach is especially suited for computing switching
controls for partial differential equations. In this case, the optimality gap
between the original functional and its relaxation can be estimated and shown
to be zero for controls with switching structure. Numerical examples illustrate
the effectiveness of this approach
Homogeneous K\"ahler and Hamiltonian manifolds
We consider actions of reductive complex Lie groups on K\"ahler
manifolds such that the --action is Hamiltonian and prove then that the
closures of the --orbits are complex-analytic in . This is used to
characterize reductive homogeneous K\"ahler manifolds in terms of their
isotropy subgroups. Moreover we show that such manifolds admit --moment maps
if and only if their isotropy groups are algebraic.Comment: 12 pages. The statement of Theorem 3.5 has been improve
Total variation regularization of multi-material topology optimization
This work is concerned with the determination of the diffusion coefficient
from distributed data of the state. This problem is related to homogenization
theory on the one hand and to regularization theory on the other hand. An
approach is proposed which involves total variation regularization combined
with a suitably chosen cost functional that promotes the diffusion coefficient
assuming prespecified values at each point of the domain. The main difficulty
lies in the delicate functional-analytic structure of the resulting
nondifferentiable optimization problem with pointwise constraints for functions
of bounded variation, which makes the derivation of useful pointwise optimality
conditions challenging. To cope with this difficulty, a novel reparametrization
technique is introduced. Numerical examples using a regularized semismooth
Newton method illustrate the structure of the obtained diffusion coefficient.
The influence of endosome-disruptive peptides on gene transfer using synthetic virus-like gene transfer systems
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