In this study, we first build two empirical cross-correlationmatrices in the US stockmarket by two different methods, namely the Pearson’s correlation coefficient and the detrended cross-correlation coefficient (DCCA coefficient). Then, combining the twomatriceswith the method of random matrix theory (RMT), we mainly investigate the statistical properties of cross-correlations in the US stock m...

assessment of the correlation between rock brittleness and rock fracture toughness has been the subject of extensive research works in the recent years. unfortunately, the brittleness measurement methods have not yet been standardized, and rock fracture toughness cannot be estimated satisfactorily by the proposed indices. in the present study, statistical analyses are performed on some data col...

Multiplicity of the effective factors in drilling reflects the complexity of the interaction between rock mass and drilling bit, which is followed by the dependence of parameters and non-linear relationships between them. Rock mass or, in other words, the formation intended for drilling, as the drilling environment, plays a very essential role in the drilling speed, depreciation of drilling bit...

An impressive volume of careful empirical studies finds evidence that the strength of firms’ corporate governance tends to be positively correlated with their financial performance; that is, firms that score higher on some measure of governance tend to outperform those which score worse. These findings are a puzzle insofar as we expect those who decide how a firm is organized, including its cor...

Recent empirical work using panel data documents that, while the correlation of investment and Tobin’s Q is low, the correlation of investment and credit spreads is high. We propose an explanation for these empirical findings, based on time-varying risk, i.e. stochastic volatility. In our model, firms finance investments using defaultable debt as well as equity issuance, and they are subject to...

This paper explores the empirical support behind the idea that there is a trade-off between the size of the migrant population and the rights and entitlements enjoyed by immigrants. We first look at the empirical correlation between measures of migrants’ rights and the size of the stock of immigrants in a number of existing databases. Using data on migrants’ rights from three recent studies—the...

Robustness and evolvability are fundamental characteristics of life whose relationship has intrigued generations of biologists. Studies of several genotype-phenotype maps (GPMs) such as the map between short DNA sequences and their bindings to transcription factors showed that phenotype robustness (PR) promotes phenotype evolvability (PE), but the underlying reason is unclear. Here, we show mat...