Darwinian Selection and Non-existence of Nash Equilibria

We study selection acting on phenotype in a collection of agents playing local games lacking Nash equilibria. After each cycle one of the agents losing most games is replaced by a new agent with new random strategy and game partner. The network generated can be considered critical in the sense that the lifetimes of the agents is power law distributed. The longest surviving agents are those with the lowest absolute score per time step. The emergent ecology is characterized by a broad range of behaviors. Nevertheless, the agents tend to be similar to their opponents in terms of performance.Comment: 4 pages, 5 figure

The weakly perturbed Schwarzschild lens in the strong deflection limit

We investigate the strong deflection limit of gravitational lensing by a Schwarzschild black hole embedded in an external gravitational field. The study of this model, analogous to the Chang & Refsdal lens in the weak deflection limit, is important to evaluate the gravitational perturbations on the relativistic images that appear in proximity of supermassive black holes hosted in galactic centers. By a simple dimensional argument, we prove that the tidal effect on the light ray propagation mainly occurs in the weak field region far away from the black hole and that the external perturbation can be treated as a weak field quadrupole term. We provide a description of relativistic critical curves and caustics and discuss the inversion of the lens mapping. Relativistic caustics are shifted and acquire a finite diamond shape. Sources inside the caustics produce four sequences of relativistic images. On the other hand, retro-lensing caustics are only shifted while remaining point-like to the lowest order.Comment: 12 pages, 1 figure

A Review Paper on Sustainable Cost Effective Concrete for Corrosive Environment

For its favorable properties and easily availability, the use of concrete increasing annually. When the concrete exposed to environment it start to disintegrate due to chemical attack. The chemical attacks on concrete majorly are in the form of a reaction between aggressive agents and the cement matrix, although reactions can also happen with the aggregates. This review paper gives a suggestion to make a cost effective and durable concrete to perform well in the aggressive corrosion environment by the waste products obtained from different industry. The use of Portland cement concrete has an impact on the environmental due to the emission of CO2 in the atmosphere. On the other side handling of plastic waste was a major problem all over the world. So, as to give suggestion to these problems the study has been made as the use of rice husk ash (obtained from agricultural waste) and silica fume (obtained from alloy industry) as partial replacement of Portland cement to increase strength at early and later ages. And due to its micro structure it reduce the permeability of concrete and exhibit considerable enhancement in durability, also provides better bond between cement matrix and the aggregate. The usage of LDPE is high throughout the world compared to other plastics, the density of LDPE range from 925-940 kg/m3 so the density of the concrete greatly reduce up to 30%  as their wastes can be used as a replacement for fine aggregate.. In terms of durability the high amount of silica impregnated the concrete samples and thereby reduces porosity of concrete. The strength reduction due to plastics will nearly   compensated by the RHA and SF. The use of such waste products gives cost effective and reducing co2 emission and best method for the disposal of plastic wastes. Keywords: Silica Fume, Rice husk ash, LDPE, Durability DOI: 10.7176/CER/11-5-05 Publication date:June 30th 201

The Exchange Gate in Solid State Spin Quantum Computation: The Applicability of the Heisenberg Model

Solid state quantum computing proposals rely on adiabatic operations of the exchange gate among localized spins in nanostructures. We study corrections to the Heisenberg interaction between lateral semiconductor quantum dots in an external magnetic field. Using exact diagonalization we obtain the regime of validity of the adiabatic approximation. We also find qualitative corrections to the Heisenberg model at high magnetic fields and in looped arrays of spins. Looped geometries of localized spins generate flux dependent, multi-spin terms which go beyond the basic Heisenberg model.Comment: 13 pages, 8 figure

Inversion improves the recognition of facial expression in thatcherized images

The Thatcher illusion provides a compelling example of the face inversion effect. However, the marked effect of inversion in the Thatcher illusion contrasts to other studies that report only a small effect of inversion on the recognition of facial expressions. To address this discrepancy, we compared the effects of inversion and thatcherization on the recognition of facial expressions. We found that inversion of normal faces caused only a small reduction in the recognition of facial expressions. In contrast, local inversion of facial features in upright thatcherized faces resulted in a much larger reduction in the recognition of facial expressions. Paradoxically, inversion of thatcherized faces caused a relative increase in the recognition of facial expressions. Together, these results suggest that different processes explain the effects of inversion on the recognition of facial expressions and on the perception of the Thatcher illusion. The grotesque perception of thatcherized images is based on a more orientation-sensitive representation of the face. In contrast, the recognition of facial expression is dependent on a more orientation-insensitive representation. A similar pattern of results was evident when only the mouth or eye region was visible. These findings demonstrate that a key component of the Thatcher illusion is to be found in orientation-specific encoding of the features of the face

First phylogenetic analyses of galaxy evolution

The Hubble tuning fork diagram, based on morphology, has always been the preferred scheme for classification of galaxies and is still the only one originally built from historical/evolutionary relationships. At the opposite, biologists have long taken into account the parenthood links of living entities for classification purposes. Assuming branching evolution of galaxies as a "descent with modification", we show that the concepts and tools of phylogenetic systematics widely used in biology can be heuristically transposed to the case of galaxies. This approach that we call "astrocladistics" has been first applied to Dwarf Galaxies of the Local Group and provides the first evolutionary galaxy tree. The cladogram is sufficiently solid to support the existence of a hierarchical organization in the diversity of galaxies, making it possible to track ancestral types of galaxies. We also find that morphology is a summary of more fundamental properties. Astrocladistics applied to cosmology simulated galaxies can, unsurprisingly, reconstruct the correct "genealogy". It reveals evolutionary lineages, divergences from common ancestors, character evolution behaviours and shows how mergers organize galaxy diversity. Application to real normal galaxies is in progress. Astrocladistics opens a new way to analyse galaxy evolution and a path towards a new systematics of galaxies

Bond Strength of Grouted Reinforcing Bars

The effects of hole preparation method, grout type, hole diameter, bar size, embedment length, cover, bar surface condition (epoxy-coated or ncoated), orientation of the installed bar, and concrete strength on the bond strength of grouted reinforcing bars are described. Hole preparation methods, using a high-speed vacuum drill or a hand-held electric hammer drill, and cleaning methods, using a fiber bottle brush with water, a fiber bottle brush without water, or compressed air only are compared. Two capsule systems, two two-component grout systems, and two nonshrink grout systems are evaluated. Hole diameters range from 3/4 to 1-1/2 in. (19 to 38 mm) for No. 5 (16 mm) bars; a hole diameter of 1-1/4 in. (32 mm) is used for No. 8 (25 mm) bars. Embedment lengths range from 4 to 12 in. (102 to 305 mm) for No. 5 (16 mm) bars and from 6 to 15 in. (150 to 380 mm) for No. (25 mm) bars. 1-1/2 and 3 in. (38 and 75 mm) covers are used. Bar installations include vertical, sloped, and horizontal bars. Test results are used to develop rational design and construction requirements. The bond strength of grouted reinforcing bars is not highly sensitive to differences in the hole preparation or cleaning methods studied. Grouts that provide strong bond at the grout-concrete interface provide higher bond strengths than grouts that undergo failure at the grout-concrete interface. With the exception of bars anchored by capsule systems, the bond strength provided by grouts is not sensitive to hole diameter. Bond strength increases with increasing embedment length, cover, and bar size. The bond strength of grouted reinforcement is insensitive to the presence of epoxy coating. Vertically and horizontally anchored bars may exhibit different bond strengths, depending on the grout used

Kerr black hole lensing for generic observers in the strong deflection limit

We generalize our previous work on gravitational lensing by a Kerr black hole in the strong deflection limit, removing the restriction to observers on the equatorial plane. Starting from the Schwarzschild solution and adding corrections up to the second order in the black hole spin, we perform a complete analytical study of the lens equation for relativistic images created by photons passing very close to a Kerr black hole. We find out that, to the lowest order, all observables (including shape and shift of the black hole shadow, caustic drift and size, images position and magnification) depend on the projection of the spin on a plane orthogonal to the line of sight. In order to break the degeneracy between the black hole spin and its inclination relative to the observer, it is necessary to push the expansion to higher orders. In terms of future VLBI observations, this implies that very accurate measures are needed to determine these two parameters separately.Comment: 17 pages, 4 figures, one section added, to appear on Physical Review

Scale-free networks are not robust under neutral evolution

Recently it has been shown that a large variety of different networks have power-law (scale-free) distributions of connectivities. We investigate the robustness of such a distribution in discrete threshold networks under neutral evolution. The guiding principle for this is robustness in the resulting phenotype. The numerical results show that a power-law distribution is not stable under such an evolution, and the network approaches a homogeneous form where the overall distribution of connectivities is given by a Poisson distribution.Comment: Submitted for publicatio