420 research outputs found
Regulatory estimates for defaulted exposures: A case study of Spanish mortgages
The capital requirements derived from the Basel Accord were issued with the purpose of
deploying a transnational regulatory framework. Further regulatory developments on risk measurement
is included across several documents published both by the European Banking Authority and
the European Central Bank. Among others, the referred additional documentation focused on the
models’ estimation and calibration for credit risk measurement purposes, especially the Advanced
Internal-Ratings Based models, which may be estimated both for non-defaulted and defaulted assets.
A concrete proposal of the referred defaulted exposures models, namely the Expected Loss Best Estimate
(ELBE) and the Loss Given Default (LGD) in-default, is presented. The proposed methodology
is eventually calibrated on the basis of data from the mortgage’s portfolios of the six largest financial
institutions in Spain. The outcome allows for a comparison of the risk profile particularities attached
to each of the referred portfolios. Eventually, the economic sense of the results is analyzed.Regional Government of Andalusia, Spain (Research Group SEJ-555)
Forecasting for regulatory credit loss derived from the COVID-19 pandemic: A machine learning approach
The economic onslaught of the COVID-19 pandemic has compromised the risk management of financial institutions. The consequences related to such an unprecedented situation are difficult to foresee with certainty using traditional methods. The regulatory credit loss attached to defaulted mortgages, so-called expected loss best estimate (ELBE), is forecasted using a machine learning technique. The projection of two ELBEs for 2022 and their comparison are presented. One accounts for the outbreak’s impact, and the other presumes the nonexistence of the pandemic. Then, it is concluded that the referred crisis surely adversely affects said high-risk portfolios. The proposed method has excellent performance and may serve to estimate future expected and unexpected losses amidst any event of extraordinary magnitud
Evolution of the Schr\"odinger--Newton system for a self--gravitating scalar field
Using numerical techniques, we study the collapse of a scalar field
configuration in the Newtonian limit of the spherically symmetric
Einstein--Klein--Gordon (EKG) system, which results in the so called
Schr\"odinger--Newton (SN) set of equations. We present the numerical code
developed to evolve the SN system and topics related, like equilibrium
configurations and boundary conditions. Also, we analyze the evolution of
different initial configurations and the physical quantities associated to
them. In particular, we readdress the issue of the gravitational cooling
mechanism for Newtonian systems and find that all systems settle down onto a
0--node equilibrium configuration.Comment: RevTex file, 19 pages, 26 eps figures. Minor changes, matches version
to appear in PR
Scalar Field as Dark Matter in the Universe
We investigate the hypothesis that the scalar field is the dark matter and
the dark energy in the Cosmos, wich comprises about 95% of the matter of the
Universe. We show that this hypothesis explains quite well the recent
observations on type Ia supernovae.Comment: 4 pages REVTeX, 1 eps figure. Minor changes. To appear in Classical
and Quantum Gravit
Newtonian Collapse of Scalar Field Dark Matter
In this letter, we develop a Newtonian approach to the collapse of galaxy
fluctuations of scalar field dark matter under initial conditions inferred from
simple assumptions. The full relativistic system, the so called
Einstein-Klein-Gordon, is reduced to the Schr\"odinger-Newton one in the weak
field limit. The scaling symmetries of the SN equations are exploited to track
the non-linear collapse of single scalar matter fluctuations. The results can
be applied to both real and complex scalar fields.Comment: 4 pages RevTex4 file, 4 eps figure
Longitudinal Bone Loss Occurs at the Radius in CKD.
Chronic kidney disease (CKD) exposes to an increased incidence of fragility fractures. International guidelines recommend performing bone mineral density (BMD) if the results will impact treatment decisions. It remains unknown where bone loss occurs and what would preclude the longitudinal loss in patients with CKD. Here, we aimed to investigate factors influencing BMD and to analyze the longitudinal BMD changes.
In the NephroTest cohort, we measured BMD at the femoral neck, total hip, lumbar spine, and proximal radius, together with circulating biomarkers and standardized measured glomerular filtration rate (mGFR) by <sup>51</sup> Cr-EDTA in a subset of patients with CKD stage 1 to 5 followed during 4.3 ± 2.0 years. A linear mixed model explored the longitudinal bone loss and the relationship of associated factors with BMD changes. A total of 858 patients (mean age 58.9 ± 15.2 years) had at least 1 and 477 had at least 2 BMD measures.
At baseline, cross-sectional analysis showed a significantly lower BMD at femoral neck and total hip and a significant higher serum parathyroid hormone (PTH) along with CKD stages. Baseline age, gender, tobacco, low body mass index (BMI), and high PTH levels were significantly associated with low BMD. Longitudinal analysis during the mean 4.3 years revealed a significant bone loss at the radius only. BMD changes at the femoral neck were associated with BMI, but not CKD stages or basal PTH levels.
CKD is associated with low BMD and high PTH in the cross-sectional analysis. Longitudinal bone loss occurred at the proximal radius after 4.3 years
Quintessence and Scalar Dark Matter in the Universe
Continuing with previous works, we present a cosmological model in which dark
matter and dark energy are modeled by scalar fields and ,
respectively, endowed with the scalar potentials and . This model contains 95% of
scalar field. We obtain that the scalar dark matter mass is The solution obtained allows us to recover the success of the
standard CDM. The implications on the formation of structure are reviewed. We
obtain that the minimal cutoff radio for this model is Comment: 4 pages REVTeX, 3 eps color figures. Minor changes and references
updated. To appear in Classical and Quantum Gravity as a Letter to the
Editor. More information at http://www.fis.cinvestav.mx/~siddh/PHI
Galactic Collapse of Scalar Field Dark Matter
We present a scenario for galaxy formation based on the hypothesis of scalar
field dark matter. We interpret galaxy formation through the collapse of a
scalar field fluctuation. We find that a cosh potential for the
self-interaction of the scalar field provides a reasonable scenario for
galactic formation, which is in agreement with cosmological observations and
phenomenological studies in galaxies.Comment: 4 pages, 3 figue
Oscillons in dilaton-scalar theories
It is shown by both analytical methods and numerical simulations that
extremely long living spherically symmetric oscillons appear in virtually any
real scalar field theory coupled to a massless dilaton (DS theories). In fact
such "dilatonic" oscillons are already present in the simplest non-trivial DS
theory -- a free massive scalar field coupled to the dilaton. It is shown that
in analogy to the previously considered cases with a single nonlinear scalar
field, in DS theories there are also time periodic quasibreathers (QB)
associated to small amplitude oscillons. Exploiting the QB picture the
radiation law of the small amplitude dilatonic oscillons is determined
analytically.Comment: extended discussion on stability, to appear in JHEP, 29 pages, 7
figure
On the Space Time of a Galaxy
We present an exact solution of the averaged Einstein's field equations in
the presence of two real scalar fields and a component of dust with spherical
symmetry. We suggest that the space-time found provides the characteristics
required by a galactic model that could explain the supermassive central object
and the dark matter halo at once, since one of the fields constitutes a central
oscillaton surrounded by the dust and the other scalar field distributes far
from the coordinate center and can be interpreted as a halo. We show the
behavior of the rotation curves all along the background. Thus, the solution
could be a first approximation of a ``long exposition photograph'' of a galaxy.Comment: 8 pages REVTeX, 11 eps figure
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