7,896 research outputs found
Competition and Financial Stability in European Cooperative Banks
Cooperative banks are a driving force for socially committed business at the local level, accounting for around one fifth of the European Union (EU) bank deposits and loans. Despite their importance, little is known about the relationship between bank stability and competition for these small credit institutions. Does
competition affect the stability of cooperative banks? Does the financial stability of banks increase/decrease when competition is higher? We assess the dynamic relationship between competition and bank soundness (both in the short and long run) among European cooperative banks between 1998 and 2009. We obtain three main results. First, we provide evidence in line with the competition-stability view proposed by Boyd and De Nicolò (2005). Bank market power negatively “Granger-causes” banks’soundness, meaning that there is a positive relationship between competition and stability. Second, we find that this fundamental relationship does not change during the 2007–2009 financial
crisis. Third, we show that increased homogeneity in the cooperative banking sector positively affects bank soundness. Our findings have important policy implications for designing and
implementing regulations that enhance the overall stability of the financial system and in particular of the cooperative banking sector
BPS domain walls in N=4 supergravity and dual flows
We establish the conditions for supersymmetric domain wall solutions to N=4
gauged supergravity in five dimensions. These read as BPS first-order equations
for the warp factor and the scalar fields, driven by a superpotential and
supplemented by a set of constraints that we specify in detail. Then we apply
our results to certain consistent truncations of IIB supergravity, thus
exploring their dual field theory renormalization group flows. We find a
universal flow deforming superconformal theories on D3-branes at Calabi-Yau
cones. Moreover, we obtain a superpotential for the solution corresponding to
the baryonic branch of the Klebanov-Strassler theory, as well as the
superpotential for the flow describing D3 and wrapped D5-branes on the resolved
conifold.Comment: 42 pages, 1 figure. v2: minor changes, matches published versio
Bootstrapping the 3d Ising twist defect
Recent numerical results point to the existence of a conformally invariant
twist defect in the critical 3d Ising model. In this note we show that this
fact is supported by both epsilon expansion and conformal bootstrap
calculations. We find that our results are in good agreement with the numerical
data. We also make new predictions for operator dimensions and OPE coefficients
from the bootstrap approach. In the process we derive universal bounds on
one-dimensional conformal field theories and conformal line defects.Comment: 24+8 pages, 12 figures, references adde
Thermodynamic Bubble Ansatz
Motivated by the computation of scattering amplitudes at strong coupling, we
consider minimal area surfaces in AdS_5 which end on a null polygonal contour
at the boundary. We map the classical problem of finding the surface into an
SU(4) Hitchin system. The polygon with six edges is the first non-trivial
example. For this case, we write an integral equation which determines the area
as a function of the shape of the polygon. The equations are identical to those
of the Thermodynamics Bethe Ansatz. Moreover, the area is given by the free
energy of this TBA system. The high temperature limit of the TBA system can be
exactly solved. It leads to an explicit expression for a special class of
hexagonal contours.Comment: 55 pages, 22 figures. v2: references added, V3: small typo fixe
An algorithm for constructing certain differential operators in positive characteristic
Given a non-zero polynomial in a polynomial ring with coefficients in
a finite field of prime characteristic , we present an algorithm to compute
a differential operator which raises to its th power. For
some specific families of polynomials, we also study the level of such a
differential operator , i.e., the least integer such that
is -linear. In particular, we obtain a characterization of
supersingular elliptic curves in terms of the level of the associated
differential operator.Comment: 23 pages. Comments are welcom
Unified Dark Matter scalar field models with fast transition
We investigate the general properties of Unified Dark Matter (UDM) scalar
field models with Lagrangians with a non-canonical kinetic term, looking
specifically for models that can produce a fast transition between an early
Einstein-de Sitter CDM-like era and a later Dark Energy like phase, similarly
to the barotropic fluid UDM models in JCAP1001(2010)014. However, while the
background evolution can be very similar in the two cases, the perturbations
are naturally adiabatic in fluid models, while in the scalar field case they
are necessarily non-adiabatic. The new approach to building UDM Lagrangians
proposed here allows to escape the common problem of the fine-tuning of the
parameters which plague many UDM models. We analyse the properties of
perturbations in our model, focusing on the the evolution of the effective
speed of sound and that of the Jeans length. With this insight, we can set
theoretical constraints on the parameters of the model, predicting sufficient
conditions for the model to be viable. An interesting feature of our models is
that what can be interpreted as w_{DE} can be <-1 without violating the null
energy conditions.Comment: Slightly revised version accepted for publication in JCAP, with a few
added references; 27 pages, 13 figure
- …