Gradient-based approaches to direct policy search in reinforcement learning have received much recent attention as a means to solve problems of partial observability and to avoid some of the problems associated with policy degradation in value-function methods. In this paper we introduce GPOMDP,...

We report some numerical simulations to investigate the existence of a self-organized critical (SOC) state in a random-neighbor version of the OFC model for a range of parameters corresponding to a non-conservative case. In contrast to a recent work, we do not find any evidence of SOC. We use a...

We present a model for the distribution of family names that explains the power-law decay of the probability distribution for the number of people with a given family name. The model includes a description of the process of generation or importation of new names, and a description of the growth...

After a brief overview of classical techniques used to explore cardiac rhythm variability, we show how the DFA method can help diagnose heart failure.

We consider different models of stochastic dissipative equations and theoretically compute the probability distribution functions (actually the associated large deviation functions) of the time averaged injected power required to sustain a nontrivial stationary state. We discuss the results and...

We introduce two new measures of network robustness and apply them to four different strategies. The measures are independent from the number of nodes in the network and have the strong potential to cover a large portfolio of applications. Using the Monte-Carlo methods, we demonstrate how to...

In this paper we propose a statistical physics approach to experimental results on bacterial mutations (Escherichia coli). We get scaling laws that describe some generic traits and suggest some features of the underlying dynamical structure for the considered evolution process. Our main...

Purpose – The purpose of the paper, in this two-part series, is to consider certain intriguing aspects of randomness, the basic mathematical concept used to model financial risk and other unknown quantities in the physical world. Design/methodology/approach – In Part 2 of the paper, the...

Purpose – Recent research indicates that the random walk hypothesis (RWH) approximately describes the behavior of major dollar exchange rates during the post-1973 float. The present analysis seeks to examine the profitability of currency futures trading rules that assume that spot exchange...