38,045 research outputs found
Fundamental Framework for Technical Analysis
Starting from the characterization of the past time evolution of market
prices in terms of two fundamental indicators, price velocity and price
acceleration, we construct a general classification of the possible patterns
characterizing the deviation or defects from the random walk market state and
its time-translational invariant properties. The classification relies on two
dimensionless parameters, the Froude number characterizing the relative
strength of the acceleration with respect to the velocity and the time horizon
forecast dimensionalized to the training period. Trend-following and contrarian
patterns are found to coexist and depend on the dimensionless time horizon. The
classification is based on the symmetry requirements of invariance with respect
to change of price units and of functional scale-invariance in the space of
scenarii. This ``renormalized scenario'' approach is fundamentally
probabilistic in nature and exemplifies the view that multiple competing
scenarii have to be taken into account for the same past history. Empirical
tests are performed on on about nine to thirty years of daily returns of twelve
data sets comprising some major indices (Dow Jones, SP500, Nasdaq, DAX, FTSE,
Nikkei), some major bonds (JGB, TYX) and some major currencies against the US
dollar (GBP, CHF, DEM, JPY). Our ``renormalized scenario'' exhibits
statistically significant predictive power in essentially all market phases. In
constrast, a trend following strategy and trend + acceleration following
strategy perform well only on different and specific market phases. The value
of the ``renormalized scenario'' approach lies in the fact that it always finds
the best of the two, based on a calculation of the stability of their predicted
market trajectories.Comment: Latex, 27 page
Is the Redshift Clustering of Long-Duration Gamma-Ray Bursts Significant?
The 26 long-duration gamma-ray bursts (GRBs) with known redshifts form a
distinct cosmological set, selected differently than other cosmological probes
such as quasars and galaxies. Since the progenitors are now believed to be
connected with active star-formation and since burst emission penetrates dust,
one hope is that with a uniformly-selected sample, the large-scale redshift
distribution of GRBs can help constrain the star-formation history of the
Universe. However, we show that strong observational biases in ground-based
redshift discovery hamper a clean determination of the large-scale GRB rate and
hence the connection of GRBs to the star formation history. We then focus on
the properties of the small-scale (clustering) distribution of GRB redshifts.
When corrected for heliocentric motion relative to the local Hubble flow, the
observed redshifts appear to show a propensity for clustering: 8 of 26 GRBs
occurred within a recession velocity difference of 1000 km/s of another GRB.
That is, 4 pairs of GRBs occurred within 30 h_65^-1 Myr in cosmic time, despite
being causally separated on the sky. We investigate the significance of this
clustering. Comparison of the numbers of close redshift pairs expected from the
simulation with that observed shows no significant small-scale clustering
excess in the present sample; however, the four close pairs occur only in about
twenty percent of the simulated datasets (the precise significance of the
clustering is dependent upon the modeled biases). We conclude with some
impetuses and suggestions for future precise GRB redshift measurements.Comment: Published in the Astronomical Journal, June 2003: see
http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2003AJ....125.2865
Passive scalar intermittency in low temperature helium flows
We report new measurements of turbulent mixing of temperature fluctuations in
a low temperature helium gas experiment, spanning a range of microscale
Reynolds number, , from 100 to 650. The exponents of the
temperature structure functions
are shown to saturate to for the highest
orders, . This saturation is a signature of statistics dominated by
front-like structures, the cliffs. Statistics of the cliff characteristics are
performed, particularly their width are shown to scale as the Kolmogorov length
scale.Comment: 4 pages, with 4 figure
W Plus Multiple Jets at the LHC with High Energy Jets
We study the production of a W boson in association with n hard QCD jets (for
n>=2), with a particular emphasis on results relevant for the Large Hadron
Collider (7 TeV and 8 TeV). We present predictions for this process from High
Energy Jets, a framework for all-order resummation of the dominant
contributions from wide-angle QCD emissions. We first compare predictions
against recent ATLAS data and then shift focus to observables and regions of
phase space where effects beyond NLO are expected to be large.Comment: 19 pages, 9 figure
Antiferromagnetic correlations and impurity broadening of NMR linewidths in cuprate superconductors
We study a model of a d-wave superconductor with strong potential scatterers
in the presence of antiferromagnetic correlations and apply it to experimental
nuclear magnetic resonance (NMR) results on Zn impurities in the
superconducting state of YBCO. We then focus on the contribution of
impurity-induced paramagnetic moments, with Hubbard correlations in the host
system accounted for in Hartree approximation. We show that local magnetism
around individual impurities broadens the line, but quasiparticle interference
between impurity states plays an important role in smearing out impurity
satellite peaks. The model, together with estimates of vortex lattice effects,
provides a semi-quantitative description of the impurity concentration
dependence of the NMR line shape in the superconducting state, and gives a
qualitative description of the temperature dependence of the line asymmetry. We
argue that impurity-induced paramagnetism and resonant local density of states
effects are both necessary to explain existing experiments.Comment: 15 pages, 23 figures, submitted to Phys. Rev.
Phase transition in a spring-block model of surface fracture
A simple and robust spring-block model obeying threshold dynamics is
introduced to study surface fracture of an overlayer subject to stress induced
by adhesion to a substrate. We find a novel phase transition in the crack
morphology and fragment-size statistics when the strain and the substrate
coupling are varied. Across the transition, the cracks display in succession
short-range, power-law and long-range correlations. The study of stress release
prior to cracking yields useful information on the cracking process.Comment: RevTeX, 4 pages, 4 Postscript figures included using epsfi
Cold Quark Matter, Quadratic Corrections and Gauge/String Duality
We make an estimate of the quadratic correction in the pressure of cold quark
matter using gauge/string duality.Comment: 7 pages; v.2: reference added; v.3: reference and comments added,
version to appear in PRD; v4. final version to appear in PRD; v.5: key
reference adde
Dopant-modulated pair interaction in cuprate superconductors
Comparison of recent experimental STM data with single-impurity and
many-impurity Bogoliubov-de Gennes calculations strongly suggests that random
out-of-plane dopant atoms in cuprates modulate the pair interaction locally.
This type of disorder is crucial to understanding the nanoscale electronic
structure inhomogeneity observed in BSCCO-2212, and can reproduce observed
correlations between the positions of impurity atoms and various aspects of the
local density of states such as the gap magnitude and the height of the
coherence peaks. Our results imply that each dopant atom modulates the pair
interaction on a length scale of order one lattice constant.Comment: 5 pages, 4 figure
Local modulations of the spin-fluctuation mediated pairing interaction by impurities in d-wave superconductors
We present a self-consistent real space formulation of spin-fluctuation
mediated d-wave pairing. By calculating all relevant inhomogeneous spin and
charge susceptibilities in real space within the random phase approximation
(RPA), we obtain the effective pairing interaction and study its spatial
dependence near both local potential and hopping impurities. A remarkably large
enhancement of the pairing interaction may be obtained near the impurity site.
We discuss the relevance of our result to inhomogeneities observed by scanning
tunneling spectroscopy on the surface of cuprate superconductors.Comment: 8 pages, 7 figure
- …