A Pseudo Random Numbers Generator Based on Chaotic Iterations. Application to Watermarking

In this paper, a new chaotic pseudo-random number generator (PRNG) is proposed. It combines the well-known ISAAC and XORshift generators with chaotic iterations. This PRNG possesses important properties of topological chaos and can successfully pass NIST and TestU01 batteries of tests. This makes our generator suitable for information security applications like cryptography. As an illustrative example, an application in the field of watermarking is presented.Comment: 11 pages, 7 figures, In WISM 2010, Int. Conf. on Web Information Systems and Mining, volume 6318 of LNCS, Sanya, China, pages 202--211, October 201

Microlensing of Circumstellar Disks

We investigate the microlensing effects on a source star surrounded by a circumstellar disk, as a function of wavelength. The microlensing light curve of the system encodes the geometry and surface brightness profile of the disk. In the mid- and far-infrared, the emission of the system is dominated by the thermal emission from the cold dusty disk. For a system located at the Galactic center, we find typical magnifications to be of order 10-20% or higher, depending on the disk surface brightness profile, and the event lasts over one year. At around 20 microns, where the emission for the star and the disk are comparable, the difference in the emission areas results in a chromatic microlensing event. Finally, in the near-infrared and visible, where the emission of the star dominates, the fraction of star light directly reflected by the disk slightly modifies the light curve of the system which is no longer that of a point source. In each case, the corresponding light curve can be used to probe some of the disk properties. A fraction of 0.1% to 1% optical microlensing events are expected to be associated with circumstellar disk systems. We show that the lensing signal of the disk can be detected with sparse follow-up observations of the next generation space telescopes. While direct imaging studies of circumstellar disks are limited to the solar neighborhood, this microlensing technique can probe very distant disk systems living in various environments and has the potential to reveal a larger diversity of circumstellar disks.Comment: 9 pages, 7 figures. Accepted for publication in Ap

Networking Effects on Cooperation in Evolutionary Snowdrift Game

The effects of networking on the extent of cooperation emerging in a competitive setting are studied. The evolutionary snowdrift game, which represents a realistic alternative to the well-known Prisoner's Dilemma, is studied in the Watts-Strogatz network that spans the regular, small-world, and random networks through random re-wiring. Over a wide range of payoffs, a re-wired network is found to suppress cooperation when compared with a well-mixed or fully connected system. Two extinction payoffs, that characterize the emergence of a homogeneous steady state, are identified. It is found that, unlike in the Prisoner's Dilemma, the standard deviation of the degree distribution is the dominant network property that governs the extinction payoffs.Comment: Changed conten

Characteristic Energy of the Coulomb Interactions and the Pileup of States

Tunneling data on $\mathrm{La_{1.28}Sr_{1.72}Mn_2O_7}$ crystals confirm Coulomb interaction effects through the $\sqrt{\mathrm{E}}$ dependence of the density of states. Importantly, the data and analysis at high energy, E, show a pileup of states: most of the states removed from near the Fermi level are found between ~40 and 130 meV, from which we infer the possibility of universal behavior. The agreement of our tunneling data with recent photoemission results further confirms our analysis.Comment: 4 pages, 4 figures, submitted to PR