34,694 research outputs found
Global integration in the banking industry
Lowered regulatory barriers and advances in technology have reduced the cost of supplying banking services across borders. At the same time, growth in activity by multinational corporations has increased the demand for international financial services. As a result, many observers believe that global integration is under way in the banking industry, that banks are expanding their reach across borders, and that many banking markets will therefore develop large foreign components. The authors report on a study conducted by them, along with Qinglei Dai and Steven Ongena, that examined the nationality and international reach of banks that provide short-term financial services across Europe to affiliates of multinational corporations. The present article also looks at time-series data that provide a more recent look at the progress of integration in Europe. Based on a 1996 survey of more than 2,000 affiliates, the study found that an affiliate is most likely to choose a bank headquartered in the nation in which it is operating (a host-nation bank) rather than a bank headquartered in the home country of the affiliate or in a third nation. The affiliate is also more likely to select a bank limited to local or regional operations rather than one with global reach. The findings are consistent with the proposition that affiliates most value a bank that understands the culture, business practices, and regulatory conditions of the country in which the affiliate operates, and that host-nation banks possess a competitive advantage over other banks in this regard. The time-series data--on syndicated loans, foreign bank claims, and the dispersion of consumer goods prices across Europe--are also consistent with the picture drawn from the 1996 survey. The article concludes that banking markets evidently need not become more integrated even as economic activity otherwise becomes increasingly global.Banks and banking ; International finance
Description of nuclear systems with a self-consistent configuration-mixing approach. I: Theory, algorithm, and application to the C test nucleus
Although self-consistent multi-configuration methods have been used for
decades to address the description of atomic and molecular many-body systems,
only a few trials have been made in the context of nuclear structure. This work
aims at the development of such an approach to describe in a unified way
various types of correlations in nuclei, in a self-consistent manner where the
mean-field is improved as correlations are introduced. The goal is to reconcile
the usually set apart Shell-Model and Self-Consistent Mean-Field methods. This
approach is referred as "variational multiparticle-multihole configuration
mixing method". It is based on a double variational principle which yields a
set of two coupled equations that determine at the same time the expansion
coefficients of the many-body wave function and the single particle states. The
formalism is derived and discussed in a general context, starting from a
three-body Hamiltonian. Links to existing many-body techniques such as the
formalism of Green's functions are established. First applications are done
using the two-body D1S Gogny effective force. The numerical procedure is tested
on the C nucleus in order to study the convergence features of the
algorithm in different contexts. Ground state properties as well as
single-particle quantities are analyzed, and the description of the first
state is examined. This study allows to validate our numerical algorithm and
leads to encouraging results. In order to test the method further, we will
realize in the second article of this series, a systematic description of more
nuclei and observables obtained by applying the newly-developed numerical
procedure with the same Gogny force. As raised in the present work,
applications of the variational multiparticle-multihole configuration mixing
method will however ultimately require the use of an extended and more
constrained Gogny force.Comment: 22 pages, 18 figures, accepted for publication in Phys. Rev. C. v2:
minor corrections and references adde
Analysis Of Measured Transport Properties Of Domain Walls In Magnetic Nanowires And Films
Existing data for soft magnetic materials of critical current for domain-wall
motion, wall speed driven by a magnetic field, and wall electrical resistance,
show that all three observable properties are related through a single
parameter: the wall mobility . The reciprocal of represents the
strength of viscous friction between domain wall and conduction-electron gas.
And is a function of the wall width, which depends in turn on the aspect
ratio t/w, where t and w are the thickness and width of the sample. Over four
orders of magnitude of , the data for nanowires show . This dependence is in approximate agreement with the prediction
of the 1984 Berger theory based on s-d exchange. On the other hand, it is
inconsistent with the prediction of the 2004 Tatara and Kohno theory, and of
the 2004 Zhang and Li theory.Comment: 7 pages, 1 figure; submitted to Phys. Rev.
Gluon-gluon contributions to the production of continuum diphoton pairs at hadron colliders
We compute the contributions to continuum photon pair production at hadron
colliders from processes initiated by gluon-gluon and gluon-quark scattering
into two photons through a four-leg virtual quark loop. Complete two-loop cross
sections in perturbative quantum chromodynamics are combined with contributions
from soft parton radiation resummed to all orders in the strong coupling
strength. The structure of the resummed cross section is examined in detail,
including a new type of unintegrated parton distribution function affecting
azimuthal angle distributions of photons in the pair's rest frame. As a result
of this analysis, we predict diphoton transverse momentum distributions in
gluon-gluon scattering in wide ranges of kinematic parameters at the Fermilab
Tevatron collider and the CERN Large Hadron Collider.Comment: 28 pages, 11 figures; published versio
The Stellar Ages and Masses of Short GRB Host Galaxies: Investigating the Progenitor Delay Time Distribution and the Role of Mass and Star Formation in the Short GRB Rate
[Abridged] We present optical and NIR observations of 19 short GRB host
galaxies, aimed at measuring their stellar masses and population ages. The
goals of this study are to evaluate whether short GRBs track the stellar mass
distribution of galaxies, to investigate the progenitor delay time
distribution, and to explore any connection between long and short GRB
progenitors. Using single stellar population models we infer masses of
log(M/M_sun)=8.8-11.6 and population ages of tau=0.03-4.4 Gyr. We further infer
maximal masses of log(M/M_sun)=9.7-11.9 by assuming stellar population ages
equal to the age of the universe at each host's redshift. Comparing the
distribution of stellar masses to the general galaxy mass function we find that
short GRBs track the cosmic stellar mass distribution only if the late-type
hosts generally have maximal masses. However, there is an apparent dearth of
early-type hosts compared to the equal contribution of early- and late-type
galaxies to the cosmic stellar mass budget. These results suggest that stellar
mass may not be the sole parameter controlling the short GRB rate, and raise
the possibility of a two-component model with both mass and star formation
playing a role. If short GRBs in late-type galaxies indeed track the star
formation activity, the resulting typical delay time is ~0.2 Gyr, while those
in early-type hosts have a typical delay of ~3 Gyr. Using the same stellar
population models we fit the data for 22 long GRB hosts and find that they have
lower masses and younger population ages, with =9.1 and
=0.06 Gyr, respectively; their maximal masses are similarly lower,
=9.6. Most importantly, the two host populations remain distinct
even if we consider only the star-forming hosts of short GRBs, supporting our
previous findings that the progenitors of long GRBs and short GRBs in late-type
galaxies are distinct.Comment: Submitted to ApJ; 20 pages, 3 tables, 8 figure
On the push&pull protocol for rumour spreading
The asynchronous push&pull protocol, a randomized distributed algorithm for
spreading a rumour in a graph , works as follows. Independent Poisson clocks
of rate 1 are associated with the vertices of . Initially, one vertex of
knows the rumour. Whenever the clock of a vertex rings, it calls a random
neighbour : if knows the rumour and does not, then tells the
rumour (a push operation), and if does not know the rumour and knows
it, tells the rumour (a pull operation). The average spread time of
is the expected time it takes for all vertices to know the rumour, and the
guaranteed spread time of is the smallest time such that with
probability at least , after time all vertices know the rumour. The
synchronous variant of this protocol, in which each clock rings precisely at
times , has been studied extensively. We prove the following results
for any -vertex graph: In either version, the average spread time is at most
linear even if only the pull operation is used, and the guaranteed spread time
is within a logarithmic factor of the average spread time, so it is . In the asynchronous version, both the average and guaranteed spread times
are . We give examples of graphs illustrating that these bounds
are best possible up to constant factors. We also prove theoretical
relationships between the guaranteed spread times in the two versions. Firstly,
in all graphs the guaranteed spread time in the asynchronous version is within
an factor of that in the synchronous version, and this is tight.
Next, we find examples of graphs whose asynchronous spread times are
logarithmic, but the synchronous versions are polynomially large. Finally, we
show for any graph that the ratio of the synchronous spread time to the
asynchronous spread time is .Comment: 25 page
Degree Distribution of Competition-Induced Preferential Attachment Graphs
We introduce a family of one-dimensional geometric growth models, constructed
iteratively by locally optimizing the tradeoffs between two competing metrics,
and show that this family is equivalent to a family of preferential attachment
random graph models with upper cutoffs. This is the first explanation of how
preferential attachment can arise from a more basic underlying mechanism of
local competition. We rigorously determine the degree distribution for the
family of random graph models, showing that it obeys a power law up to a finite
threshold and decays exponentially above this threshold.
We also rigorously analyze a generalized version of our graph process, with
two natural parameters, one corresponding to the cutoff and the other a
``fertility'' parameter. We prove that the general model has a power-law degree
distribution up to a cutoff, and establish monotonicity of the power as a
function of the two parameters. Limiting cases of the general model include the
standard preferential attachment model without cutoff and the uniform
attachment model.Comment: 24 pages, one figure. To appear in the journal: Combinatorics,
Probability and Computing. Note, this is a long version, with complete
proofs, of the paper "Competition-Induced Preferential Attachment"
(cond-mat/0402268
Surgical approaches to adenocarcinoma of the gastroesophageal junction: the Siewert II conundrum.
BACKGROUND: The Siewert classification system for gastroesophageal junction adenocarcinoma has provided morphological and topographical information to help guide surgical decision-making. Evidence has shown that Siewert I and III tumors are distinct entities with differing epidemiologic and histologic characteristics and distinct patterns of disease progression, requiring different treatment. Siewert II tumors share some of the characteristics of type I and III lesions, and the surgical approach is not universally agreed upon. Appropriate surgical options include transthoracic esophagogastrectomy, transhiatal esophagectomy, and transabdominal extended total gastrectomy.
PURPOSE: A review of the available evidence of the surgical management of Siewert II tumors is presented.
CONCLUSIONS: Careful review of the data appear to support the fact that a satisfactory oncologic resection can be achieved via a transabdominal extended total gastrectomy with a slight advantage in terms of perioperative complications, and overall postoperative quality of life. Overall and disease-free survival compares favorably to the transthoracic approach. These results can be achieved with careful selection of patients balancing more than just the Siewert type in the decision-making but considering also preoperative T and N stages, histological type (diffuse type requiring longer margins that are not always achievable via gastrectomy), and the presence of Barrett\u27s esophagus
Fluctuation Superconductivity in Mesoscopic Aluminum Rings
Fluctuations are important near phase transitions, where they can be
difficult to describe quantitatively. Superconductivity in mesoscopic rings is
particularly intriguing because the critical temperature is an oscillatory
function of magnetic field. There is an exact theory for thermal fluctuations
in one-dimensional superconducting rings, which are therefore expected to be an
excellent model system. We measure the susceptibility of many rings, one ring
at a time, using a scanning SQUID that can isolate magnetic signals from seven
orders of magnitude larger background applied flux. We find that the
fluctuation theory describes the results and that a single parameter
characterizes the ways in which the fluctuations are especially important at
magnetic fields where the critical temperature is suppressed.Comment: Reprinted with permission from AAA
Spatio-Temporal Scaling of Solar Surface Flows
The Sun provides an excellent natural laboratory for nonlinear phenomena. We
use motions of magnetic bright points on the solar surface, at the smallest
scales yet observed, to study the small scale dynamics of the photospheric
plasma. The paths of the bright points are analyzed within a continuous time
random walk framework. Their spatial and temporal scaling suggest that the
observed motions are the walks of imperfectly correlated tracers on a turbulent
fluid flow in the lanes between granular convection cells.Comment: Now Accepted by Physical Review Letter
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