2,808 research outputs found
Financial instability from local market measures
We study the emergence of instabilities in a stylized model of a financial
market, when different market actors calculate prices according to different
(local) market measures. We derive typical properties for ensembles of large
random markets using techniques borrowed from statistical mechanics of
disordered systems. We show that, depending on the number of financial
instruments available and on the heterogeneity of local measures, the market
moves from an arbitrage-free phase to an unstable one, where the complexity of
the market - as measured by the diversity of financial instruments - increases,
and arbitrage opportunities arise. A sharp transition separates the two phases.
Focusing on two different classes of local measures inspired by real markets
strategies, we are able to analytically compute the critical lines,
corroborating our findings with numerical simulations.Comment: 17 pages, 4 figure
Asymmetric correlation matrices: an analysis of financial data
We analyze the spectral properties of correlation matrices between distinct
statistical systems. Such matrices are intrinsically non symmetric, and lend
themselves to extend the spectral analyses usually performed on standard
Pearson correlation matrices to the realm of complex eigenvalues. We employ
some recent random matrix theory results on the average eigenvalue density of
this type of matrices to distinguish between noise and non trivial correlation
structures, and we focus on financial data as a case study. Namely, we employ
daily prices of stocks belonging to the American and British stock exchanges,
and look for the emergence of correlations between two such markets in the
eigenvalue spectrum of their non symmetric correlation matrix. We find several
non trivial results, also when considering time-lagged correlations over short
lags, and we corroborate our findings by additionally studying the asymmetric
correlation matrix of the principal components of our datasets.Comment: Revised version; 11 pages, 13 figure
Dual-readout Calorimetry
The RD52 Project at CERN is a pure instrumentation experiment whose goal is
to understand the fundamental limitations to hadronic energy resolution, and
other aspects of energy measurement, in high energy calorimeters. We have found
that dual-readout calorimetry provides heretofore unprecedented information
event-by-event for energy resolution, linearity of response, ease and
robustness of calibration, fidelity of data, and particle identification,
including energy lost to binding energy in nuclear break-up. We believe that
hadronic energy resolutions of {\sigma}/E 1 - 2% are within reach for
dual-readout calorimeters, enabling for the first time comparable measurement
preci- sions on electrons, photons, muons, and quarks (jets). We briefly
describe our current progress and near-term future plans. Complete information
on all aspects of our work is available at the RD52 website
http://highenergy.phys.ttu.edu/dream/.Comment: 10 pages, 10 figures, Snowmass White pape
The Social Climbing Game
The structure of a society depends, to some extent, on the incentives of the
individuals they are composed of. We study a stylized model of this interplay,
that suggests that the more individuals aim at climbing the social hierarchy,
the more society's hierarchy gets strong. Such a dependence is sharp, in the
sense that a persistent hierarchical order emerges abruptly when the preference
for social status gets larger than a threshold. This phase transition has its
origin in the fact that the presence of a well defined hierarchy allows agents
to climb it, thus reinforcing it, whereas in a "disordered" society it is
harder for agents to find out whom they should connect to in order to become
more central. Interestingly, a social order emerges when agents strive harder
to climb society and it results in a state of reduced social mobility, as a
consequence of ergodicity breaking, where climbing is more difficult.Comment: 14 pages, 9 figure
Accounting for risk of non linear portfolios: a novel Fourier approach
The presence of non linear instruments is responsible for the emergence of
non Gaussian features in the price changes distribution of realistic
portfolios, even for Normally distributed risk factors. This is especially true
for the benchmark Delta Gamma Normal model, which in general exhibits
exponentially damped power law tails. We show how the knowledge of the model
characteristic function leads to Fourier representations for two standard risk
measures, the Value at Risk and the Expected Shortfall, and for their
sensitivities with respect to the model parameters. We detail the numerical
implementation of our formulae and we emphasizes the reliability and efficiency
of our results in comparison with Monte Carlo simulation.Comment: 10 pages, 12 figures. Final version accepted for publication on Eur.
Phys. J.
Lipofundin 20% induces hepatic lipid peroxidation in New Zealand white rabbits
ABSTRACTObjective. The aim of the present work was to evaluate the effects of Lipofundin 20% on lipid peroxidation markers in the liver of New Zealand white rabbits. Materials and methods. The animals were treated with an intravenous injection (2 ml/kg) of the lipid emulsion during 8 days through the marginal ear vein. At the end of the experiment some lipid peroxidation parameters and lipid profile were tested through spectrophotography. Results. Lipofundin was found to induce a significant (p<0.05) increase of malondialdehyde, total hydroperoxides, and peroxidation potential. Also, high levels of total cholesterol, triglycerides, LDL - cholesterol and HDL-cholesterol were observed in treated animals compared with the control group (p<0.05). Conclusions. Data proved that Lipofundin induces hepatic lipid peroxidation in rabbits, mainly through a mechanism which involves an induction of hyperlipidemi
Lipofundin 20% induces hepatic lipid peroxidation in New Zealand white rabbits
ABSTRACTObjective. The aim of the present work was to evaluate the effects of Lipofundin 20% on lipid peroxidation markers in the liver of New Zealand white rabbits. Materials and methods. The animals were treated with an intravenous injection (2 ml/kg) of the lipid emulsion during 8 days through the marginal ear vein. At the end of the experiment some lipid peroxidation parameters and lipid profile were tested through spectrophotography. Results. Lipofundin was found to induce a significant (p<0.05) increase of malondialdehyde, total hydroperoxides, and peroxidation potential. Also, high levels of total cholesterol, triglycerides, LDL - cholesterol and HDL-cholesterol were observed in treated animals compared with the control group (p<0.05). Conclusions. Data proved that Lipofundin induces hepatic lipid peroxidation in rabbits, mainly through a mechanism which involves an induction of hyperlipidemi
System Test of the ATLAS Muon Spectrometer in the H8 Beam at the CERN SPS
An extensive system test of the ATLAS muon spectrometer has been performed in
the H8 beam line at the CERN SPS during the last four years. This spectrometer
will use pressurized Monitored Drift Tube (MDT) chambers and Cathode Strip
Chambers (CSC) for precision tracking, Resistive Plate Chambers (RPCs) for
triggering in the barrel and Thin Gap Chambers (TGCs) for triggering in the
end-cap region. The test set-up emulates one projective tower of the barrel
(six MDT chambers and six RPCs) and one end-cap octant (six MDT chambers, A CSC
and three TGCs). The barrel and end-cap stands have also been equipped with
optical alignment systems, aiming at a relative positioning of the precision
chambers in each tower to 30-40 micrometers. In addition to the performance of
the detectors and the alignment scheme, many other systems aspects of the ATLAS
muon spectrometer have been tested and validated with this setup, such as the
mechanical detector integration and installation, the detector control system,
the data acquisition, high level trigger software and off-line event
reconstruction. Measurements with muon energies ranging from 20 to 300 GeV have
allowed measuring the trigger and tracking performance of this set-up, in a
configuration very similar to the final spectrometer. A special bunched muon
beam with 25 ns bunch spacing, emulating the LHC bunch structure, has been used
to study the timing resolution and bunch identification performance of the
trigger chambers. The ATLAS first-level trigger chain has been operated with
muon trigger signals for the first time
On the concentration of large deviations for fat tailed distributions, with application to financial data
Large deviations for fat tailed distributions, i.e. those that decay slower
than exponential, are not only relatively likely, but they also occur in a
rather peculiar way where a finite fraction of the whole sample deviation is
concentrated on a single variable. The regime of large deviations is separated
from the regime of typical fluctuations by a phase transition where the
symmetry between the points in the sample is spontaneously broken. For
stochastic processes with a fat tailed microscopic noise, this implies that
while typical realizations are well described by a diffusion process with
continuous sample paths, large deviation paths are typically discontinuous. For
eigenvalues of random matrices with fat tailed distributed elements, a large
deviation where the trace of the matrix is anomalously large concentrates on
just a single eigenvalue, whereas in the thin tailed world the large deviation
affects the whole distribution. These results find a natural application to
finance. Since the price dynamics of financial stocks is characterized by fat
tailed increments, large fluctuations of stock prices are expected to be
realized by discrete jumps. Interestingly, we find that large excursions of
prices are more likely realized by continuous drifts rather than by
discontinuous jumps. Indeed, auto-correlations suppress the concentration of
large deviations. Financial covariance matrices also exhibit an anomalously
large eigenvalue, the market mode, as compared to the prediction of random
matrix theory. We show that this is explained by a large deviation with excess
covariance rather than by one with excess volatility.Comment: 38 pages, 12 figure
Standalone vertex ďŹnding in the ATLAS muon spectrometer
A dedicated reconstruction algorithm to find decay vertices in the ATLAS muon spectrometer is presented. The algorithm searches the region just upstream of or inside the muon spectrometer volume for multi-particle vertices that originate from the decay of particles with long decay paths. The performance of the algorithm is evaluated using both a sample of simulated Higgs boson events, in which the Higgs boson decays to long-lived neutral particles that in turn decay to bbar b final states, and pp collision data at âs = 7 TeV collected with the ATLAS detector at the LHC during 2011
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