108 research outputs found
Credit Ratings and Bank Monitoring Ability
In this paper we use credit rating data from two Swedish banks to elicit evidence on these banksâ loan monitoring ability. We do so by comparing the ability of bank ratings to predict loan defaults relative to that of public ratings from the Swedish credit bureau. We test the banksâ abilility to forecast the credit bureauâs ratings and vice versa. We show that one of the banks has a superior predictive ability relative to the credit bureau. This is evidence that bank credit ratings do contain valuable private information and suggests they may be be a reasonable basis for risk management. However, public ratings are also found to have predictive ability for future bank ratings, indicating that risk analysis should be based on both public and bank ratings. The methods we use represent a new basket of straightforward techniques that enable both financial institutions and regulators to assess the performance of credit ratings systems.Monitoring;banks;credit bureau;private information;ratings;regulation;supervision
Credit Cycle and Adverse Selection Effects in Consumer Credit Markets â Evidence from the HELOC Market
We empirically study how the underlying riskiness of the pool of home equity line of credit originations is affected over the credit cycle. Drawing from the largest existing database of U.S. home equity lines of credit, we use county-level aggregates of these loans to estimate panel regressions on the characteristics of the borrowers and their loans, and competing risk hazard regressions on the outcomes of the loans. We show that when the expected unemployment risk of households increases, riskier households tend to borrow more. As a consequence, the pool of households that borrow on home equity lines of credit worsens along both observable and unobservable dimensions. This is an interesting example of a type of dynamic adverse selection that can worsen the risk characteristics of new lending, and suggests another avenue by which the precautionary demand for liquidity may affect borrowing.Home equity loan;adverse selection;liquidity;consumption;housing finance
Vortex phase transformations probed by the local ac response of Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta} single crystals with various doping
The linear ac response of the vortex system is measured locally in Bi-2212
single crystals at various doping, using a miniature two-coil mutual-inductance
technique. It was found that a step-like change in the local ac response takes
place exactly at the first-order transition (FOT) temperature T_{FOT}(H)
determined by a global dc magnetization measurement. The T_{FOT}(H) line in the
H-T phase diagram becomes steeper with increasing doping. In the higher-field
region where the FOT is not observed, the local ac response still shows a
broadened but distinct feature, which can be interpreted to mark the growth of
a short-range order in the vortex system.Comment: 4 pages, including 5 eps figure
Do we live in the universe successively dominated by matter and antimatter?
We wonder if a cyclic universe may be dominated alternatively by matter and
antimatter. Such a scenario demands a mechanism for transformation of matter to
antimatter (or antimatter to matter) during the final stage of a big crunch. By
giving an example, we have shown that in principle such a mechanism is
possible. Our mechanism is based on a hypothetical repulsion between matter and
antimatter, existing at least deep inside the horizon of a black hole. When
universe is reduced to a supermassive black hole of a small size, a very strong
field of the conjectured force might create (through a Schwinger type
mechanism) particle-antiparticle pairs from the quantum vacuum. The amount of
antimatter created from the vacuum is equal to the decrease of mass of the
black hole and violently repelled from it. When the size of the black hole is
sufficiently small, the creation of antimatter may become so fast, that matter
of our Universe might be transformed to antimatter in a fraction of second.
Such a fast conversion of matter into antimatter may look as a Big Bang. Our
mechanism prevents a singularity; a new cycle might start with an initial size
more than 30 orders of magnitude greater than the Planck length, suggesting
that there is no need for inflationary scenario in Cosmology. In addition,
there is no need to invoke CP violation for explanation of matter-antimatter
asymmetry. Simply, our present day Universe is dominated by matter, because the
previous universe was dominated by antimatter
Double-slit interference pattern from single-slit screen and its gravitational analogues
The double slit experiment (DSE) is known as an important cornerstone in the
foundations of physical theories such as Quantum Mechanics and Special
Relativity. A large number of different variants of it were designed and
performed over the years. We perform and discuss here a new verion with the
somewhat unexpected results of obtaining interference pattern from single-slit
screen. This outcome, which shows that the routes of the photons through the
array were changed, leads one to discuss it, using the equivalence principle,
in terms of geodesics mechanics. We show using either the Brill's version of
the canonical formulation of general relativity or the linearized version of it
that one may find corresponding and analogous situations in the framework of
general relativity.Comment: 51 pages, 12 Figures five of them contain two subfigures and thus the
number of figures is 17, 1 Table. Some minor changes introduced, especially,
in the reference
Dynamical 1/N approach to time-dependent currents through quantum dots
A systematic truncation of the many-body Hilbert space is implemented to
study how electrons in a quantum dot attached to conducting leads respond to
time-dependent biases. The method, which we call the dynamical 1/N approach, is
first tested in the most unfavorable case, the case of spinless fermions (N=1).
We recover the expected behavior, including transient ringing of the current in
response to an abrupt change of bias. We then apply the approach to the
physical case of spinning electrons, N=2, in the Kondo regime for the case of
infinite intradot Coulomb repulsion. In agreement with previous calculations
based on the non-crossing approximation (NCA), we find current oscillations
associated with transitions between Kondo resonances situated at the Fermi
levels of each lead. We show that this behavior persists for a more realistic
model of semiconducting quantum dots in which the Coulomb repulsion is finite.Comment: 18 pages, 7 eps figures, discussion extended for spinless electrons
and typo
Relativistic Hydrodynamic Evolutions with Black Hole Excision
We present a numerical code designed to study astrophysical phenomena
involving dynamical spacetimes containing black holes in the presence of
relativistic hydrodynamic matter. We present evolutions of the collapse of a
fluid star from the onset of collapse to the settling of the resulting black
hole to a final stationary state. In order to evolve stably after the black
hole forms, we excise a region inside the hole before a singularity is
encountered. This excision region is introduced after the appearance of an
apparent horizon, but while a significant amount of matter remains outside the
hole. We test our code by evolving accurately a vacuum Schwarzschild black
hole, a relativistic Bondi accretion flow onto a black hole, Oppenheimer-Snyder
dust collapse, and the collapse of nonrotating and rotating stars. These
systems are tracked reliably for hundreds of M following excision, where M is
the mass of the black hole. We perform these tests both in axisymmetry and in
full 3+1 dimensions. We then apply our code to study the effect of the stellar
spin parameter J/M^2 on the final outcome of gravitational collapse of rapidly
rotating n = 1 polytropes. We find that a black hole forms only if J/M^2<1, in
agreement with previous simulations. When J/M^2>1, the collapsing star forms a
torus which fragments into nonaxisymmetric clumps, capable of generating
appreciable ``splash'' gravitational radiation.Comment: 17 pages, 14 figures, submitted to PR
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Energetic particle influence on the Earth's atmosphere
This manuscript gives an up-to-date and comprehensive overview of the effects of energetic particle precipitation (EPP) onto the whole atmosphere, from the lower thermosphere/mesosphere through the stratosphere and troposphere, to the surface. The paper summarizes the different sources and energies of particles, principally
galactic cosmic rays (GCRs), solar energetic particles (SEPs) and energetic electron precipitation (EEP). All the proposed mechanisms by which EPP can affect the atmosphere
are discussed, including chemical changes in the upper atmosphere and lower thermosphere, chemistry-dynamics feedbacks, the global electric circuit and cloud formation. The role of energetic particles in Earthâs atmosphere is a multi-disciplinary problem that requires expertise from a range of scientific backgrounds. To assist with this synergy, summary tables are provided, which are intended to evaluate the level of current knowledge of the effects of energetic particles on processes in the entire atmosphere
Measurement of the View the tt production cross-section using eÎŒ events with b-tagged jets in pp collisions at âs = 13 TeV with the ATLAS detector
This paper describes a measurement of the inclusive top quark pair production cross-section (ÏttÂŻ) with a data sample of 3.2 fbâ1 of protonâproton collisions at a centre-of-mass energy of âs = 13 TeV, collected in 2015 by the ATLAS detector at the LHC. This measurement uses events with an opposite-charge electronâmuon pair in the final state. Jets containing b-quarks are tagged using an algorithm based on track impact parameters and reconstructed secondary vertices. The numbers of events with exactly one and exactly two b-tagged jets are counted and used to determine simultaneously ÏttÂŻ and the efficiency to reconstruct and b-tag a jet from a top quark decay, thereby minimising the associated systematic uncertainties. The cross-section is measured to be:
ÏttÂŻ = 818 ± 8 (stat) ± 27 (syst) ± 19 (lumi) ± 12 (beam) pb,
where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, the integrated luminosity and the LHC beam energy, giving a total relative uncertainty of 4.4%. The result is consistent with theoretical QCD calculations at next-to-next-to-leading order. A fiducial measurement corresponding to the experimental acceptance of the leptons is also presented
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