Trend Detection based Regret Minimization for Bandit Problems

We study a variation of the classical multi-armed bandits problem. In this problem, the learner has to make a sequence of decisions, picking from a fixed set of choices. In each round, she receives as feedback only the loss incurred from the chosen action. Conventionally, this problem has been studied when losses of the actions are drawn from an unknown distribution or when they are adversarial. In this paper, we study this problem when the losses of the actions also satisfy certain structural properties, and especially, do show a trend structure. When this is true, we show that using \textit{trend detection}, we can achieve regret of order $\tilde{O} (N \sqrt{TK})$ with respect to a switching strategy for the version of the problem where a single action is chosen in each round and $\tilde{O} (Nm \sqrt{TK})$ when $m$ actions are chosen each round. This guarantee is a significant improvement over the conventional benchmark. Our approach can, as a framework, be applied in combination with various well-known bandit algorithms, like Exp3. For both versions of the problem, we give regret guarantees also for the \textit{anytime} setting, i.e. when the length of the choice-sequence is not known in advance. Finally, we pinpoint the advantages of our method by comparing it to some well-known other strategies

Has the Structural Break Slowed Down Growth Rates of Stock Markets?

In this paper, we use the common structural break test suggested by Bai et al. (1998) to test for a common structural break in the stock prices of the US, the UK, and Japan. On the basis of the structural break, we divide each countries stock price series into sub-samples and investigate whether or not the structural break had slowed down the growth of stock markets. Our main findings are that when stock markets are modeled in a trivariate sense the common structural break turns out to be 1990:02, with the confidence interval including several episodes, such as the asset price bubble when housing prices and stock prices in Japan reached a peak in 1988/1989, the early 1990s recession in the UK, the business cycle peak of July 1990, the August 1990 Iraqi invasion of Kuwait and the March 1991 business cycle trough. Annual average growth rates suggest that the structural break has slowed down the growth rate of the UK and Japanese stock markets, while it has boosted the growth of the US stock market.Common Structural Break Test, Stock Markets

Recent advances in unstructured grid generation program VGRID3D

A program for the generation of unstructured grids over complex configurations, VGRID3D, is described. The grid elements (triangles on the surfaces and tetrahedra in the field) are generated starting from the surface boundaries towards the interior of the computational domain using the Advancing Front Method

Mean Reversion in Stock Prices: New Evidence from Panel Unit Root Tests for Seventeen European Countries

There is a large and growing literature that investigates evidence for mean reversion in stock prices. Empirically, there is no consensus as to whether stock prices are mean reverting or random walk processes at best, the results are mixed. In this paper, we provide further evidence on the mean reversion hypothesis for seventeen European countries using the Levin and Lin (1992), seemingly unrelated regression and the multivariate augmented Dickey-Fuller panel unit root tests. Our main finding is that stock prices of all seventeen European countries are characterised by a unit root, consistent with the efficient market hypothesis.

Asymmetric Information and Market Collapse

In this paper, using data for the period January 1995 to May 2009 for the Shanghai stock exchange (SHSE), we show that aggregate illiquidity is a priced risk factor. We develop the relationship between the illiquidity factor, asymmetric information, and market collapse. Our empirical results show that while the illiquidity factor is a source of asymmetric information on the SHSE, asymmetric information does not trigger a market collapse.Illiquidity Factor; Asymmetric Information; Market Collapse.

Has the structural break slowed down growth rates of stock markets?

In this paper, we use the common structural break test suggested by Bai et al. (1998) to test for a common structural break in the stock prices of the US, the UK, and Japan. On the basis of the structural break, we divide each country‟s stock price series into sub-samples and investigate whether or not the structural break had slowed down the growth of stock markets. Our main findings are that when stock markets are modeled in a trivariate sense the common structural break turns out to be 1990:02, with the confidence interval including several episodes, such as the asset price bubble when housing prices and stock prices in Japan reached a peak in 1988/1989, the early 1990s recession in the UK, the business cycle peak of July 1990, the August 1990 Iraqi invasion of Kuwait and the March 1991 business cycle trough. Annual average growth rates suggest that the structural break has slowed down the growth rate of the US, UK and Japanese stock markets.Common Structural Break Test, Stock Markets

Dead Man Walking: An Empirical Reassessment of the Deterrent Effect of Capital Punishment Using the Bounds Testing Approach to Cointegration

This paper empirically estimates a murder supply equation for the United States from 1965 to 2001 within a cointegration and error correction framework. Our findings suggest that any support for the deterrence hypothesis is sensitive to the inclusion of variables for the effect of guns and other crimes. In the long-run we find that real income and the conditional probability of receiving the death sentence are the main factors explaining variations in the homicide rate. In the short-run the aggravated assault rate and robbery rate are the most important determinants of the homicide raCapital Punishment, Deterrent Effect, Cointegration