Temporal fluctuations of current surface density in a triangular lattice

In this paper, we examine the effect of the temporal fluctuation current correlation in the surface diffusion process in a triangular lattice, in the framework of the lattice gas model. Our calculations are per found in small circular surfaces equivalent to the probe areas in the scanning microscopy experiments. We have found that the correlation function, in the non- interacting case, follows the law Öp . In the presence of repulsive interactions between mobile particles, it behaves like Öp exp(8γp). We have also calculated the collective diffusion coefficient by the linear response theory and by the characteristic time method, which reflect clearly the order-disorder effect on the diffusion.In this paper, we examine the effect of the temporal fluctuation current correlation in the surface diffusion process in a triangular lattice, in the framework of the lattice gas model. Our calculations are per found in small circular surfaces equivalent to the probe areas in the scanning microscopy experiments. We have found that the correlation function, in the non- interacting case, follows the law Öp . In the presence of repulsive interactions between mobile particles, it behaves like Öp exp(8γp). We have also calculated the collective diffusion coefficient by the linear response theory and by the characteristic time method, which reflect clearly the order-disorder effect on the diffusion

Study of adatoms diffusion through current density fluctuation functions

In this work, we investigate the diffusion process by using a mean field lattice gas dynamical model. The temporal correlation function of the current density is calculated in a probe area of radius R. The latter is considered to test if the developed formulation can be applied to reproduce STM experiments. The obtained results concerning the effective diffusion coefficient exhibit clearly the order disorder transition effect translated by two minima appearing respectively at p=1/3 and p=2/3. The effect of the ordering phase at p=1/3 requires a threshold size more precisely, the minimum size system where, the ordering phase effect begins, to appear here is R=5.In this work, we investigate the diffusion process by using a mean field lattice gas dynamical model. The temporal correlation function of the current density is calculated in a probe area of radius R. The latter is considered to test if the developed formulation can be applied to reproduce STM experiments. The obtained results concerning the effective diffusion coefficient exhibit clearly the order disorder transition effect translated by two minima appearing respectively at p=1/3 and p=2/3. The effect of the ordering phase at p=1/3 requires a threshold size more precisely, the minimum size system where, the ordering phase effect begins, to appear here is R=5

Stock return comovement around the Dow Jones Islamic Market World Index revisions

We examine patterns of comovement in stock returns around the Dow Jones Islamic Market World Index (DJIMWI) quarterly revision events. Our analysis is based on a sample of 8250 companies from eighteen countries during the period May 1999–June 2012. We find that a stock’s comovement with the DJIMWI increases when it joins and decreases when it leaves the index. We also find that the comovement of newly added (deleted) stocks with the existing DJIMWI constituents increases (declines) during periods of high trading activity and during the month of Ramadan. Further tests reveal that changes in the fundamentals have no impact on the comovements of added and deleted stocks. Overall, our results indicate that stock returns respond to the emotional state of investors around information-free events

Underwriters' allocation with and without discretionary power: Evidence from the Hong Kong IPO market

This study uses a unique and extensive data set from the Hong Kong IPO market to examine the theory of adverse selection under two distinct regulatory regimes in relation to underwriters' discretionary power in IPO share allocation. Consistent with Rock's (1986) theory of adverse selection in the IPO market, we show that, prior to the introduction of the clawback provision; retail (uninformed) investors were allocated more of the overpriced offerings and less of the underpriced issues. However, after the provision is implemented, retail investors have been allocated significantly more of the underpriced offerings and less of the overpriced ones. Overall, we find that allocation-adjusted initial returns for the retail investors are lower (higher) than the risk-free rate pre- (post-) clawback provision. These findings imply that the mandatory clawback provision has enhanced the fairness in IPO share allocations among different investor groups and has reduced the winner's curse in the IPO market

Stock price reaction to profit warnings: The role of time-varying betas

This study investigates the role of time-varying betas, event-induced variance and conditional heteroskedasticity in the estimation of abnormal returns around important news announcements. Our analysis is based on the stock price reaction to profit warnings issued by a sample of firms listed on the Hong Kong Stock Exchange. The standard event study methodology indicates the presence of price reversal patterns following both positive and negative warnings. However, incorporating time-varying betas, event-induced variance and conditional heteroskedasticity in the modelling process results in post-negative-warning price patterns that are consistent with the predictions of the efficient market hypothesis. These adjustments also cause the statistical significance of some post-positive-warning cumulative abnormal returns to disappear and their magnitude to drop to an extent that minor transaction costs would eliminate the profitability of the contrarian strategy