Correlated Gaussian method for dilute bosonic systems

The weakly interacting trapped Bose gases have been customarily described using the mean-field approximation in the form of the Gross-Pitaevskii equation. The mean-field approximation, however, has certain limitations, in particular it can not describe correlations between particles. We introduce here an alternative variational approach, based on the correlated Gaussian method, which in its simplest form is as fast and simple as the mean-field approximation, but which allows successive improvements of the trial wave-function by including correlations between particles.Comment: 9 pages, Workshop on Nuclei and Mesoscopic Physics, NSCL MSU, 200

Inverse Statistics for Stocks and Markets

In recent publications, the authors have considered inverse statistics of the Dow Jones Industrial Averaged (DJIA) [1-3]. Specifically, we argued that the natural candidate for such statistics is the investment horizons distribution. This is the distribution of waiting times needed to achieve a predefined level of return obtained from detrended historic asset prices. Such a distribution typically goes through a maximum at a time coined the {\em optimal investment horizon}, $\tau^*_\rho$, which defines the most likely waiting time for obtaining a given return $\rho$. By considering equal positive and negative levels of return, we reported in [2,3] on a quantitative gain/loss asymmetry most pronounced for short horizons. In the present paper, this gain/loss asymmetry is re-visited for 2/3 of the individual stocks presently in the DJIA. We show that this gain/loss asymmetry established for the DJIA surprisingly is {\em not} present in the time series of the individual stocks. The most reasonable explanation for this fact is that the gain/loss asymmetry observed in the DJIA as well as in the SP500 and Nasdaq are due to movements in the market as a whole, {\it i.e.}, cooperative cascade processes (or ``synchronization'') which disappear in the inverse statistics of the individual stocks.Comment: Revtex 13 pages, including 15 figure

The Two-Body Random Ensemble in Nuclei

Combining analytical and numerical methods, we investigate properties of the two-body random ensemble (TBRE). We compare the TBRE with the Gaussian orthogonal ensemble of random matrices. Using the geometric properties of the nuclear shell model, we discuss the information content of nuclear spectra, and gain insight in the difficulties encountered when fitting the effective interaction. We exhibit the existence of correlations between spectral widths pertaining to different quantum numbers. Using these results, we deduce the preponderance of spin-zero ground states in the TBRE. We demonstrate the existence of correlations between spectra with different quantum numbers and/or in different nuclei.Comment: 16 pages, 13 figure

TECHNICAL EFFICIENCY OF GRAIN PRODUCTION IN UKRAINE

A stochastic grain production frontier model is estimated on a representative sample of Ukrainian state farms. Technical inefficiency effects are modeled as a function of workforce composition, other farm-specific variables, and time. Technical inefficiency increased over time. Investment in farm infrastructure is associated with higher levels of technical efficiency.Productivity Analysis,

Investigation of thermionic energy conversion final report, 9 jul. - 9 sep. 1962

Refractory ceramic oxide for thermionic diode

AGRICULTURAL HOUSEHOLD MODEL WITH WAGE UNCERTAINTY: AN APPLICATION TO SUBSIDIARY POST-SOVIET AGRICULTURE

The labor supply decision under wage uncertainty is studied in the context of an agricultural household model. The recent sharp growth of post-Soviet subsidiary subsistence agriculture is consistent with the model predictions of an increase in farm labor supply in response to the fall and uncertainty in real wage.Consumer/Household Economics, Labor and Human Capital,

Low-density series expansions for directed percolation II: The square lattice with a wall

A new algorithm for the derivation of low-density expansions has been used to greatly extend the series for moments of the pair-connectedness on the directed square lattice near an impenetrable wall. Analysis of the series yields very accurate estimates for the critical point and exponents. In particular, the estimate for the exponent characterizing the average cluster length near the wall, $\tau_1=1.00014(2)$, appears to exclude the conjecture $\tau_1=1$. The critical point and the exponents $\nu_{\parallel}$ and $\nu_{\perp}$ have the same values as for the bulk problem.Comment: 8 pages, 1 figur

Dimensional reduction in a model with infinitely many absorbing states

Using Monte Carlo method we study a two-dimensional model with infinitely many absorbing states. Our estimation of the critical exponent beta=0.273(5) suggests that the model belongs to the (1+1) rather than (2+1) directed-percolation universality class. We also show that for a large class of absorbing states the dynamic Monte Carlo method leads to spurious dynamical transitions.Comment: 6 pages, 4 figures, Phys.Rev. E, Dec. 199

Welfare Reform and Labor Participation: Are There Urban and Rural Differences?

Although welfare reform began in 1996 at the national level, Iowa was one of the earliest states to obtain a waiver to initiate the Iowa Family Investment Program (FIP) in 1993. To gain a better understanding of welfare recidivism, we use Iowa administrative quarterly data between October1993 and September 1995, impute the education attainment for the caseheads with missing education attainment using fractional imputation and study the factors that affect the probability of working, the potential wage for the caseheads and the possibility of leaving FIP based on the potential wage. We find higher education (i.e. higher skills) leads to higher labor force participation, especially for single-mothers with children. Metro or urban location is associated with the probability of working and potential wage earnings, but has no effect on FIP participation. The local unemployment rate does not affect labor participation of low-income individuals, but does affect the potential wage and FIP status. Those with lower education, and nonwhites are more affected by the local labor market environment than others. If an individual moves once in a year, he or she will earn more money than in the original job; no gains are achieved through moving more than once. The possibility of leaving FIP is relatively high if there is only one move.Labor and Human Capital,