7,736 research outputs found
Crude Oil and Stock Markets: Stability, Instability, and Bubbles
We analyze the long-run relationship between the world price of crude oil and international stock markets over 1971:1-2008:3 using a cointegrated vector error correction model with additional regressors. Allowing for endogenously identified breaks in the cointegrating and error correction matrices, we find evidence for breaks after 1980:5, 1988:1, and 1999:9. We find a clear long-run relationship between these series for six OECD countries for 1971:1-1980.5 and 1988:2-1999.9, suggesting that stock market indices respond negatively to increases in the oil price in the long run. During 1980.6-1988.1, we find relationships that are not statistically significantly different from either zero or from the relationships of the previous period. The expected negative long-run relationship appears to disintegrate after 1999.9. This finding supports a conjecture of change in the relationship between real oil price and real stock prices in the last decade compared to earlier years, which may suggest the presence of several stock market bubbles and/or oil price bubbles since the turn of the century.crude oil, stock market prices, cointegrated VECM, structural stability, stock market bubble, oil price bubble
The problem of repulsive quark interactions - Lattice versus mean field models
We calculate the 2nd and 4th order quark number susceptibilities at zero
baryochemical potential, using a PNJL approach and an approach which includes,
in a single model, quark and hadronic degrees of freedom. We observe that the
susceptibilities are very sensitive to possible quark-quark vector
interactions. Compared to lattice data our results suggest that above any
mean field type of repulsive vector interaction can be excluded from model
calculations. Below our results show only very weak sensitivity on the
strength of the quark and hadronic vector interaction. The best description of
lattice data around is obtained for a case of coexistence of hadronic and
quark degrees of freedom.Comment: 5 pages, 4 figure, version accepted by PL
A PNJL model in 0+1 Dimensions
We formulate the Polyakov-Nambu-Jona-Lasinio (PNJL) model in 0+1 dimensions.
The thermodynamics captured by the partition function yields a bulk pressure,
as well as quark susceptibilities versus temperature that are similar to the
ones in 3+1 dimensions. Around the transition temperature the behavior in the
pressure and quark susceptibilities follows from the interplay between the
lowest Matsubara frequency and the Polyakov line. The reduction to the lowest
Matsubara frequency yields a matrix Model. In the presence of the Polyakov line
the UV part of the Dirac spectrum features oscillations when close to the
transition temperature.Comment: 18 pages, 13 figure
Mol-CycleGAN - a generative model for molecular optimization
Designing a molecule with desired properties is one of the biggest challenges
in drug development, as it requires optimization of chemical compound
structures with respect to many complex properties. To augment the compound
design process we introduce Mol-CycleGAN - a CycleGAN-based model that
generates optimized compounds with high structural similarity to the original
ones. Namely, given a molecule our model generates a structurally similar one
with an optimized value of the considered property. We evaluate the performance
of the model on selected optimization objectives related to structural
properties (presence of halogen groups, number of aromatic rings) and to a
physicochemical property (penalized logP). In the task of optimization of
penalized logP of drug-like molecules our model significantly outperforms
previous results
The QCD phase diagram from analytic continuation
We present the crossover line between the quark gluon plasma and the hadron
gas phases for small real chemical potentials. First we determine the effect of
imaginary values of the chemical potential on the transition temperature using
lattice QCD simulations. Then we use various formulas to perform an analytic
continuation to real values of the baryo-chemical potential. Our data set
maintains strangeness neutrality to match the conditions of heavy ion physics.
The systematic errors are under control up to MeV. For the
curvature of the transition line we find that there is an approximate agreement
between values from three different observables: the chiral susceptibility,
chiral condensate and strange quark susceptibility. The continuum extrapolation
is based on 10, 12 and 16 lattices. By combining the analysis for these
three observables we find, for the curvature, the value .Comment: 14 pages, 4 figures, revised versio
The QCD equation of state at finite density from analytical continuation
We determine the equation of state of QCD at finite chemical potential, to
order , for a system of 2+1 quark flavors. The simulations are
performed at the physical mass for the light and strange quarks on several
lattice spacings; the results are continuum extrapolated using lattices of up
to temporal resolution. The QCD pressure and interaction measure are
calculated along the isentropic trajectories in the plane
corresponding to the RHIC Beam Energy Scan collision energies. Their behavior
is determined through analytic continuation from imaginary chemical potentials
of the baryonic density. We also determine the Taylor expansion coefficients
around from the simulations at imaginary chemical potentials.
Strangeness neutrality and charge conservation are imposed, to match the
experimental conditions.Comment: 5 pages, 4 figure
Towards the QCD phase diagram from analytical continuation
We calculate the QCD cross-over temperature, the equation of state and
fluctuations of conserved charges at finite density by analytical continuation
from imaginary to real chemical potentials. Our calculations are based on new
continuum extrapolated lattice simulations using the 4stout staggered actions
with a lattice resolution up to . The simulation parameters are tuned
such that the strangeness neutrality is maintained, as it is in heavy ion
collisions.Comment: 4 pages, 2 figures, Proceedings of the Quark Matter 2015 conference,
Kobe, Japa
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