1,585 research outputs found
Repo Runs
This paper develops a model of financial institutions that borrow short- term and invest into long-term marketable assets. Because these financial intermediaries perform maturity transformation, they are subject to runs. We endogenize the profits of the intermediary and derive distinct liquidity and solvency conditions that determine whether a run can be prevented. We first characterize these conditions for an isolated intermediary and then generalize them to the case where the intermediary can sell assets to prevent runs. The sale of assets can eliminate runs if the intermediary is solvent but illiquid. However, because of cash-in-the-market pricing, this becomes less likely the more intermediaries are facing problems. In the limit, in case of a general market run, no intermediary can sell assets to forestall a run, and our original solvency and liquidity constraints are again relevant for the stability of financial institutions.Investment banking;securities dealers;repurchase agreements;tri-party repo;runs;financial fragility
Low mass lepton pair production in hadron collisions
The hadroproduction of lepton pairs with mass and transverse momentum
can be described in perturbative QCD by the same partonic subprocesses as
prompt photon production. We demonstrate that, like prompt photon production,
lepton pair production is dominated by quark-gluon scattering in the region
. This leads to sensitivity to the gluon density in kinematical
regimes that are accessible both at collider and fixed target experiments while
eliminating the theoretical and experimental uncertainties present in prompt
photon production.Comment: Talk given by M. Klasen at the International Conference on the
Structure and Interactions of the Photon, PHOTON 99, Freiburg i. Brsg.,
Germany, May 23-27, 1999. To be published in the proceedings. 6 pages, 6
postscript figure
Virtual photon fragmentation functions
We introduce operator definitions for virtual photon fragmentation functions,
which are needed for reliable calculations of Drell-Yan transverse momentum
() distributions when is much larger than the invariant mass . We
derive the evolution equations for these fragmentation functions. We calculate
the leading order evolution kernels for partons to fragment into a unpolarized
as well as a polarized virtual photon. We find that fragmentation functions to
a longitudinally polarized virtual photon are most important at small , and
the fragmentation functions to a transversely polarized virtual photon dominate
the large region. We discuss the implications of this finding to the
J/ mesons' polarization at large transverse momentum.Comment: Latex, 19 pages including 6 figures. An error in the first version
has been corrected, and references update
A new numerical method for obtaining gluon distribution functions , from the proton structure function
An exact expression for the leading-order (LO) gluon distribution function
from the DGLAP evolution equation for the proton structure
function for deep inelastic scattering has
recently been obtained [M. M. Block, L. Durand and D. W. McKay, Phys. Rev.
D{\bf 79}, 014031, (2009)] for massless quarks, using Laplace transformation
techniques. Here, we develop a fast and accurate numerical inverse Laplace
transformation algorithm, required to invert the Laplace transforms needed to
evaluate , and compare it to the exact solution. We obtain accuracies
of less than 1 part in 1000 over the entire and spectrum. Since no
analytic Laplace inversion is possible for next-to-leading order (NLO) and
higher orders, this numerical algorithm will enable one to obtain accurate NLO
(and NNLO) gluon distributions, using only experimental measurements of
.Comment: 9 pages, 2 figure
Recommended from our members
Burning questions: Investigations using field experimentation of different patterns of change to bone in accidental vs deliberate burning scenarios.
Experimental research into thermal alterations to bone has tended to be carried out under laboratory conditions, where different burning scenarios are simulated to reconstruct the respective heat-induced changes in bone. While this approach has greatly advanced this field of research, very little open-air field experimentation has been conducted and consequently documented. The current paper presents the results of the first study to utilise field experimentation to examine the heat-induced alterations that occur in bone when subjected to two different firing conditions. This experiment contrasted a reconstruction of a funeral pyre with a simulated house fire in order to explore differences in the effects of accidental and deliberate burning scenarios on bone. Both advantages and problems faced are discussed with regards to the methodological approach used to document and analyse the resultant burned bone; leading to recommendations for future research. The burned bone assemblage from the accidental fire displayed uneven burning, with an extensive spectrum of colour alteration. Bone fragments recovered from the funeral pyre however showed distinctly uniform thermal changes, with minimal variation. This research demonstrates the value of field experimentation in the analysis of burned bone from both archaeological and forensic contexts. Insight into both ancient and modern households and their subjectivity to domestic fires, as well as the social and ritual implications of past cremation funerals are considered. It is concluded that future research would greatly benefit from employing a similar mode of investigation, in conjunction with laboratory experimentation
Magnetic-field dependence of electron spin relaxation in n-type semiconductors
We present a theoretical investigation of the magnetic field dependence of
the longitudinal () and transverse () spin relaxation times of
conduction band electrons in n-type III-V semiconductors. In particular, we
find that the interplay between the Dyakonov-Perel process and an additional
spin relaxation channel, which originates from the electron wave vector
dependence of the electron -factor, yields a maximal at a finite
magnetic field. We compare our results with existing experimental data on
n-type GaAs and make specific additional predictions for the magnetic field
dependence of electron spin lifetimes.Comment: accepted for publication in PRB, minor changes to previous manuscrip
Running into New Territory in SUSY Parameter Space
The LEP-II bound on the light Higgs mass rules out the vast majority of
parameter space left to the Minimal Supersymmetric Standard Model (MSSM) with
weak-scale soft-masses. This suggests the importance of exploring extensions of
the MSSM with non-minimal Higgs physics. In this article, we explore a theory
with an additional singlet superfield and an extended gauge sector. The theory
has a number of novel features compared to both the MSSM and Next-to-MSSM,
including easily realizing a light CP-even Higgs mass consistent with LEP-II
limits, tan(beta) < 1, and a lightest Higgs which is charged. These features
are achieved while remaining consistent with perturbative unification and
without large stop-masses. Discovery modes at the Tevatron and LHC are
discussed.Comment: 15 pages, 5 figures; Typo in equation (4.5) corrected; submitted to
JHE
Have precipitation extremes and annual totals been increasing in the world’s dry regions over the last 60 years?
Daily precipitation extremes and annual totals have increased in large parts of the global land area over the past decades. These observations are consistent with theoretical considerations of a warming climate. However, until recently these trends have not been shown to consistently affect dry regions over land. A recent study, published by Donat et al. (2016), now identified significant increases in annual-maximum daily extreme precipitation (Rx1d) and annual precipitation totals (PRCPTOT) in dry regions. Here, we revisit the applied methods and explore the sensitivity of changes in precipitation extremes and annual totals to alternative choices of defining a dry region (i.e. in terms of aridity as opposed to precipitation characteristics alone). We find that (a) statistical artifacts introduced by data pre-processing based on a time-invariant reference period lead to an overestimation of the reported trends by up to 40 %, and that (b) the reported trends of globally aggregated extremes and annual totals are highly sensitive to the definition of a "dry region of the globe". For example, using the same observational dataset, accounting for the statistical artifacts, and based on different aridity-based dryness definitions, we find a reduction in the positive trend of Rx1d from the originally reported +1.6 % decade−1 to +0.2 to +0.9 % decade−1 (period changes for 1981–2010 averages relative to 1951–1980 are reduced to −1.32 to +0.97 % as opposed to +4.85 % in the original study). If we include additional but less homogenized data to cover larger regions, the global trend increases slightly (Rx1d: +0.4 to +1.1 % decade−1), and in this case we can indeed confirm (partly) significant increases in Rx1d. However, these globally aggregated estimates remain uncertain as considerable gaps in long-term observations in the Earth's arid and semi-arid regions remain. In summary, adequate data pre-processing and accounting for uncertainties regarding the definition of dryness are crucial to the quantification of spatially aggregated trends in precipitation extremes in the world's dry regions. In view of the high relevance of the question to many potentially affected stakeholders, we call for a well-reflected choice of specific data processing methods and the inclusion of alternative dryness definitions to guarantee that communicated results related to climate change be robust.Have precipitation extremes and annual totals been increasing in the world’s dry regions over the last 60 years?publishedVersio
Investigation of a hydraulic impact: a technology in rock breaking
The finite element method and dimensional analysis have been applied in the
present paper to study a hydraulic impact, which is utilized in a non-explosive
rock breaking technology in mining industry. The impact process of a high speed
piston on liquid water, previously introduced in a borehole drilled in rock, is
numerically simulated. The research is focused on the influences of all the
parameters involved in the technology on the largest principal stress in the
rock, which is considered as one of the key factors to break the rock. Our
detailed parametric investigation reveals that the variation of the isotropic
rock material properties, especially its density, has no significant influence
on the largest principal stress. The influences of the depth of the hole and
the depth of the water column are also very small. On the other hand,
increasing the initial kinetic energy of the piston can dramatically increase
the largest principal stress and the best way to increase the initial kinetic
energy of the piston is to increase its initial velocity. Results from the
current dimensional analysis can be applied to optimize this non-explosive rock
breaking technology
Next-to-leading order QCD corrections to A_TT for prompt photon production
We present a next-to-leading order QCD calculation of the cross section for
isolated large-p_T prompt photon production in collisions of transversely
polarized protons. We devise a simple method of dealing with the phase space
integrals in dimensional regularization in the presence of the cos(2 phi)
azimuthal-angular dependence occurring for transverse polarization. Our results
allow to calculate the double-spin asymmetry A_TT for this process at
next-to-leading order accuracy, which may be used at BNL-RHIC to measure the
transversity parton distributions of the proton.Comment: 19 pages, LaTeX, 2 figures as eps file
- …