Mutual correlation in the shock wave geometry

We probe the shock wave geometry with the mutual correlation in a spherically symmetric Reissner Nordstr\"om AdS black hole on the basis of the gauge/gravity duality. In the static background, we find that the regions living on the boundary of the AdS black holes are correlated provided the considered regions on the boundary are large enough. We also investigate the effect of the charge on the mutual correlation and find that the bigger the value of the charge is, the smaller the value of the mutual correlation will to be. As a small perturbation is added at the AdS boundary, the horizon shifts and a dynamical shock wave geometry forms after long time enough. In this dynamic background, we find that the greater the shift of the horizon is, the smaller the mutual correlation will to be. Especially for the case that the shift is large enough, the mutual correlation vanishes, which implies that the considered regions on the boundary are uncorrelated. The effect of the charge on the mutual correlation in this dynamic background is found to be the same as that in the static background.Comment: 10 page

Comparative Analysis of Peak Correlation Characteristics of Non-Orthogonal Spreading Codes for Wireless Systems

The performance of a CDMA based wireless system is largely dependent on the characteristics of pseudo-random spreading codes. The spreading codes should be carefully chosen to ensure highest possible peak value of auto-correlation function and lower correlation peaks (side-lobes) at non-zero time-shifts. Simultaneously, zero cross-correlation value at all time shifts is required in order to eliminate the effect of multiple access interference at the receiver. But no such code family exists which possess both characteristics simultaneously. That's why an exhaustive effort has been made in this paper to evaluate the peak correlation characteristics of various non-orthogonal spreading codes and suggest a suitable solution.Comment: 12 Pages, 8 Figures, 3 Table

Bose-glass to Superfluid transition in the three-dimensional Bose-Hubbard Model

We present a Monte Carlo study of the Bose-glass to superfluid transition in the three-dimensional Bose-Hubbard model. Simulations are performed on the classical (3 + 1) dimensional link-current representation using the geometrical worm algorithm. Finite-size scaling analysis (on lattices as large as 16x16x16x512 sites) of the superfluid stiffness and the compressibility is consistent with a value of the dynamical critical exponent z = 3, in agreement with existing scaling and renormalization group arguments that z = d. We find also a value of $\nu = 0.70(12)$ for the correlation length exponent, satisfying the relation $\nu >= 2/d$. However, a detailed study of the correlation functions, C(r, tau), at the quantum critical point are not consistent with this value of z. We speculate that this discrepancy could be due to the fact that the correlation functions have not reached their true asymptotic behavior because of the relatively small spatial extent of the lattices used in the present study.Comment: 9 pages, 8 figures, submitted to PR

Dynamical Properties of Heavy-Ion Collisions from the Photon-Photon Intensity Correlations

We consider here the bremsstrahlung emission of photons at low and intermediate energies $E_{lab}\le 1000 MeV/u$ of the projectile. and derive expressions more general than previous results obtained by Neuhauser which were limited to the case of isotropic systems. We find that the two-photon correlation function strongly depends not only on the space-time properties of the collision region but also on the dynamics of the proton-neutron scattering process in nuclear matter. As a consequence of polarisation correlations it turns out that for a purely chaotic source the intercept of the correlation function of photons can reach the value $3$ (as compared with the maximum value $2$ for isotropic systems). Furthermore even for ``hard" photons ($E_{\gamma} > 25 MeV$) the maximum of the correlation function can reach the value of $2$ in contrast with the value of $1.5$ derived by Neuhauser for this case. The formulae obtained in this paper which include also the possible presence of a coherent component can be used as a basis for a systematic analysis of photon intensity-interferometry experiments.Comment: 12 pages, LaTeX, DMR-THEP-93-2/

Extreme correlation of international equity markets

Testing the hypothesis that international equity market correlation increases in volatile times is a difficult exercise and misleading results have often been reported in the past because of a spurious relationship between correlation and volatility. This paper focuses on extreme correlation, that is to say the correlation between returns in either the negative or positive tail of the multivariate distribution. Using "extreme value theory" to model the multivariate distribution tails, we derive the distribution of extreme correlation for a wide class of return distributions. Using monthly data on the five largest stock markets from 1958 to 1996, we reject the null hypothesis of multivariate normality for the negative tail, but not for the positive tail. We also find that correlation is not related to market volatility per se but to the market trend. Correlation increases in bear markets, but not in bull markets.International equity markets; volatility; correlation and extreme value theory

Effects of television advertising on children: with special reference to pakistani urban children

The purpose of study is to deliberate upon the impacts of television advertising on children & to identify those critical impacts which lead to behavioral and eating disorder in children. Impacts of TV advertising were identified as unnecessary purchasing, low nutritional food and materialism. A questionnaire using five point likert scale was administered to 425 parents of children aged between 9-14 years, and studying in schools. Samples were drawn through convenience sampling approach from four cities of Pakistan namely Islamabad, Rawalpindi, Bahawalpur & Multan. Data were analyzed by using SPSS software. Pearson correlation was used to measure the relationships of the variables on one-to-one basis indicating the most correlated variable was Unnecessary Purchasing which had Pearson correlation value of 0.312 and significance value of 0.000. It was followed by a Materialism which had Pearson correlation value of 0.260 and significance value of 0.000. Then comes Low Nutritional Food being Pearson correlation value of 0.258 and significance value of 0.000. Testing of hypothesis found that television advertising increases the consumption of food that is unhealthy, having low nutritional values and high in Sugar, Fat and Salt (SFS) in children with F=30.146 & P=0.000. Subsequently, it was found that Television advertising leads to increase in unnecessary purchasing in children with F= 45.747 & P=0.000 and materialism in children with F=30.545 & P=0.000. So, it is summed up that TV advertising is affecting children by increasing their food consumption pattern, preference for low-nutrient, high in sugar, fat & salt (SFS) foods and beverages, change in attitude that is aggressive and violent in nature and inclination towards unnecessary purchasing

計量経済学における相関有無の判定基準への疑問

In econometrics it is important to distinguish whether two variables are correlated or not. Distribution of correlation coefficient of n pairs of samples from two independent normal populations is theoretically known. Based on the distribution and the value of the sample correlation coefficient we decide whether the two variables are correlated or not. We compute distribution of correlation coefficient of n pairs of samples from two independent uniform populations by computer simulation. We see that we cannot distinguish the two distributions of the correlation coefficients when n11, however, the two distributions are different definitely