2,346 research outputs found
Competition and stability: what's special about banking?
This paper examines the relationship between competition policies and policies to preserve stability in the banking sector. Market structures and the relative importance of the three classical antitrust areas for banking are discussed, showing the predominance of merger review considerations for loan and deposit markets as well as the relevance of cartel considerations for payment systems. A core part of the paper is an analysis of the relative roles of competition and supervisory authorities in the review of bank mergers for the G-7 industrialised countries. A wide variety of approaches emerges, with some countries giving a stronger role to prudential supervisors than to competition authorities and other countries doing it the other way round. In search for explanations for this diversity the theoretical and empirical literature on the competition-stability nexus in banking is surveyed. It turns out that the widely accepted trade-off between competition and stability does not generally hold. JEL Classification: G21, G28, G34, K21, L4antitrust policies, Bank competition, banking supervision, financial stability, mergers & acquisitions
Correlator expansion approach to stationary states of weakly coupled cavity arrays
We introduce a method for calculating the stationary state of a translation
invariant array of weakly coupled cavities in the presence of dissipation and
coherent as well as incoherent drives. Instead of computing the full density
matrix our method directly calculates the correlation functions which are
relevant for obtaining all local quantities of interest. It considers an
expansion of the correlation functions and their equations of motion in powers
of the photon tunneling rate between adjacent cavities, leading to an exact
second order solution for any number of cavities. Our method provides a
controllable approximation for weak tunneling rates applicable to the strongly
correlated regime that is dominated by nonlinearities in the cavities and thus
of high interest.Comment: contribution to J. Phys. B special issue celebrating Jaynes-Cummings
physic
The economic impact of merger control legislation
Based on a unique dataset of legislative changes in industrial countries, we identify events that strengthen the competition control of mergers and acquisitions, analyze their impact on banks and non-financial firms and explain the different reactions observed with specific regulatory characteristics of the banking sector. Covering nineteen countries for the period 1987 to 2004, we find that more competition-oriented merger control increases the stock prices of banks and decreases the stock prices of non-financial firms. Bank targets become more profitable and larger, while those of non-financial firms remain mostly unaffected. A major determinant of the positive bank returns is the degree of opaqueness that characterizes the institutional setup for supervisory bank merger reviews. The legal design of the supervisory control of bank mergers may therefore have important implications for real activity
Photon correlations from ultra-strong optical nonlinearities
We study the full field and frequency filtered output photon statistics of a
resonator in thermal equilibrium with a bath and containing an arbitrarily
large quartic nonlinearity. According to the general theory of photodetection,
we derive general input-output relations valid for the ultra-anharmonic regime,
where the nonlinearity becomes comparable to the energy of the resonator, and
show how the emission properties are modified as compared to the generally
assumed simple anharmonic regime. We analyse the impact of the nonlinearity on
the full statistics of the emission and its spectral properties. In particular
we derive a semi-analytical expression for the frequency resolved two-photon
correlations or two-photon spectrum of the system in terms of the master
equation coefficients and density matrix. This provides a very clear insight
into the level structure and emission possibilities of the system.Comment: 10 pages, 7 figure
Theory of frequency-filtered and time-resolved N-photon correlations
A theory of correlations between N photons of given frequencies and detected
at given time delays is presented. These correlation functions are usually too
cumbersome to be computed explicitly. We show that they are obtained exactly
through intensity correlations between two-level sensors in the limit of their
vanishing coupling to the system. This allows the computation of correlation
functions hitherto unreachable. The uncertainties in time and frequency of the
detection, which are necessary variables to describe the system, are intrinsic
to the theory. We illustrate the formalism with the Jaynes--Cummings model,
showing how correlations of various peaks at zero or finite time delays bring
new insights into the dynamics of open quantum systems.Comment: 12 pages, 2 figure
Low-temperature lattice effects in the spin-liquid candidate -(BEDT-TTF)Cu(CN)
The quasi-two-dimensional organic charge-transfer salt
-(BEDT-TTF)Cu(CN) is one of the prime candidates for a
quantum spin-liquid due the strong spin frustration of its anisotropic
triangular lattice in combination with its proximity to the Mott transition.
Despite intensive investigations of the material's low-temperature properties,
several important questions remain to be answered. Particularly puzzling are
the 6\,K anomaly and the enigmatic effects observed in magnetic fields. Here we
report on low-temperature measurements of lattice effects which were shown to
be particularly strongly pronounced in this material (R. S. Manna \emph{et
al.}, Phys. Rev. Lett. \textbf{104}, 016403 (2010)). A special focus of our
study lies on sample-to-sample variations of these effects and their
implications on the interpretation of experimental data. By investigating
overall nine single crystals from two different batches, we can state that
there are considerable differences in the size of the second-order phase
transition anomaly around 6\,K, varying within a factor of 3. In addition, we
find field-induced anomalies giving rise to pronounced features in the sample
length for two out of these nine crystals for temperatures 9 K. We
tentatively assign the latter effects to -induced magnetic clusters
suspected to nucleate around crystal imperfections. These -induced effects
are absent for the crystals where the 6\,K anomaly is most strongly pronounced.
The large lattice effects observed at 6\,K are consistent with proposed pairing
instabilities of fermionic excitations breaking the lattice symmetry. The
strong sample-to-sample variation in the size of the phase transition anomaly
suggests that the conversion of the fermions to bosons at the instability is
only partial and to some extent influenced by not yet identified
sample-specific parameters
A new chronology for the Moon and Mercury
In this paper we present a new method for dating the surface of the Moon,
obtained by modeling the incoming flux of impactors and converting it into a
size distribution of resulting craters. We compare the results from this model
with the standard chronology for the Moon showing their similarities and
discrepancies. In particular, we find indications of a non-constant impactor
flux in the last 500 Myr and also discuss the implications of our findings for
the Late Heavy Bombardment hypothesis. We also show the potential of our model
for accurate dating of other inner Solar System bodies, by applying it to
Mercury.Comment: 27 pages, 13 figures, 1 table; accepted by A
Microbiota-Dependent Immune Responses to Intestinal Parasites
The digestive tract plays a central role in nutrient acquisition and harbors a vast and intricate community of bacteria, fungi, viruses and parasites, collectively known as the microbiota. In recent years, there has been increasing recognition of the complex and highly contextual involvement of this microbiota in the induction and education of host innate and adaptive immune responses under homeostasis, during infection and inflammation. The gut passage and colonization by unicellular and multicellular parasite species present an immense challenge to the host immune system and to the microbial communities that provide vital support for its proper functioning. In mammals, parasitic nematodes induce distinct shifts in the intestinal microbial composition. Vice versa, the commensal microbiota has been shown to serve as a molecular adjuvant and immunomodulator during intestinal parasite infections. Moreover, similar interactions occur within insect vectors of deadly human pathogens. The gut microbiota has emerged as a crucial factor affecting vector competence in Anopheles mosquitoes, where it modulates outcomes of infections with malaria parasites. In this review, we discuss currently known involvements of the host microbiota in the instruction, support or suppression of host immune responses to gastrointestinal nematodes and protozoan parasites in mice, as well as in the malaria mosquito vector. A deeper understanding of the mechanisms underlying microbiota-dependent modulation of host and vector immunity against parasites in mammals and mosquitoes is key to a better understanding of the host-parasite relationships and the identification of more efficient approaches for intervention and treatment of parasite infections of both clinical and veterinary importance
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