21,371 research outputs found
Holographic Thermalization in Charged Dilaton Anti-de Sitter Spacetime
We study holographic thermalization in spacetimes with a chemical potential
and a non-trivial dilaton field. Three non-local observables are used to probe
the whole process and investigate the effect of the ratio of the chemical
potential over temperature and the dilaton-Maxwell coupling constant
. It is found that the saturation time is not always a monotonically
increasing function of , the situation depends on . When , larger yields longer saturation time, while for
, the situation becomes more complex. More interesting, we found that
although indeed has influence on the whole thermalization process, it
nearly does not affect the saturation time, which indicates the universality of
the saturation time for the dual one-parameter field theories.Comment: 22 pages, 5 figure
Strong correlations generically protect d-wave superconductivity against disorder
We address the question of why strongly correlated d-wave superconductors,
such as the cuprates, prove to be surprisingly robust against the introduction
of non-magnetic impurities. We show that, very generally, both the
pair-breaking and the normal state transport scattering rates are significantly
suppressed by strong correlations effects arising in the proximity to a Mott
insulating state. We also show that the correlation-renormalized scattering
amplitude is generically enhanced in the forward direction, an effect which was
previously often ascribed to the specific scattering by charged impurities
outside the copper-oxide planes.Comment: 4+e page
Efficient iterative method for solving the Dirac-Kohn-Sham density functional theory
We present for the first time an efficient iterative method to directly solve
the four-component Dirac-Kohn-Sham (DKS) density functional theory. Due to the
existence of the negative energy continuum in the DKS operator, the existing
iterative techniques for solving the Kohn-Sham systems cannot be efficiently
applied to solve the DKS systems. The key component of our method is a novel
filtering step (F) which acts as a preconditioner in the framework of the
locally optimal block preconditioned conjugate gradient (LOBPCG) method. The
resulting method, dubbed the LOBPCG-F method, is able to compute the desired
eigenvalues and eigenvectors in the positive energy band without computing any
state in the negative energy band. The LOBPCG-F method introduces mild extra
cost compared to the standard LOBPCG method and can be easily implemented. We
demonstrate our method in the pseudopotential framework with a planewave basis
set which naturally satisfies the kinetic balance prescription. Numerical
results for Pt, Au, TlF, and BiSe indicate that the
LOBPCG-F method is a robust and efficient method for investigating the
relativistic effect in systems containing heavy elements.Comment: 31 pages, 5 figure
THE DESIGN AND PRICING OF FIXED AND MOVING WINDOW CONTRACTS: AN APPLICATION OF ASIAN-BASKET OPTION PRICING METHODS TO THE HOG FINISHING SECTOR
Asian-Basket type moving window contracts are an increasingly used risk management tool in US hog sector. The moving window contract is decomposed into a portfolio of a long Asian-Basket put and a short Asian-Basket call option. A projected breakeven price is used to determine the floor price, and then Monte Carlo simulation methods are used to price both a moving and a fixed window contract. These methods provide unbiased pricing of fixed and moving window hog finishing contracts of one-year duration.Livestock Production/Industries,
Underpinnings for Prospective, Net Revenue Forecasting in Hog Finishing: Characterizing the Joint Distribution of Corn, Soybean Meal and Lean Hogs Time Series
This research focuses on developing a biannual net revenue forecasting model for hog producers based on Monte Carlo simulation of the joint distribution of hog, corn and soybean meal price series. The relative forecasting power of historical volatility, implied volatility and GARCH-based volatility is examined. Consistent with recent research, the performance of these three methods is both commodity and horizon specific, which means there is no single best predictor. However, implied volatility often performs well. Thus, implied volatility is used to forecast variance. Historical covariance is introduced to capture the co-movement of the three price series. Our forecasting model performs well out of sample; most of the realized net revenues fall in 95 percent prediction interval. Based on this forecasting model and the assumption of a utility function, we compare our prospective evaluation with retrospective evaluation of risk management strategies. Though prospective evaluation is not significantly superior to retrospective evaluation for this particular dataset, it is useful because all the market information has been incorporated in this model and because it did protect producers from adverse price movements.Agricultural Finance, Livestock Production/Industries,
Bringing closure to microlensing mass measurement
Interferometers offer multiple methods for studying microlensing events and
determining the properties of the lenses. We investigate the study of
microlensing events with optical interferometers, focusing on narrow-angle
astrometry, visibility, and closure phase. After introducing the basics of
microlensing and interferometry, we derive expressions for the signals in each
of these three channels. For various forecasts of the instrumental performance,
we discuss which method provides the best means of measuring the lens angular
Einstein radius theta_E, a prerequisite for determining the lens mass. If the
upcoming generation of large-aperture, AO-corrected long baseline
interferometers (e.g. VLTI, Keck, OHANA) perform as well as expected, theta_E
may be determined with signal-to-noise greater than 10 for all bright events.
We estimate that roughly a dozen events per year will be sufficiciently bright
and have long enough durations to allow the measurement of the lens mass and
distance from the ground. We also consider the prospects for a VLTI survey of
all bright lensing events using a Fisher matrix analysis, and find that even
without individual masses, interesting constraints may be placed on the bulge
mass function, although large numbers of events would be required.Comment: 23 pages, aastex, submitted to Ap
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