How effective is advertising in duopoly markets?

A simple Ising spin model which can describe the mechanism of advertising in a duopoly market is proposed. In contrast to other agent-based models, the influence does not flow inward from the surrounding neighbors to the center site, but spreads outward from the center to the neighbors. The model thus describes the spread of opinions among customers. It is shown via standard Monte Carlo simulations that very simple rules and inclusion of an external field -- an advertising campaign -- lead to phase transitions.Comment: 7 pages, 6 figures; v2: cosmetic change

Majority versus minority dynamics: Phase transition in an interacting two-state spin system

We introduce a simple model of opinion dynamics in which binary-state agents evolve due to the influence of agents in a local neighborhood. In a single update step, a fixed-size group is defined and all agents in the group adopt the state of the local majority with probability p or that of the local minority with probability 1-p. For group size G=3, there is a phase transition at p_c=2/3 in all spatial dimensions. For p>p_c, the global majority quickly predominates, while for p<p_c, the system is driven to a mixed state in which the densities of agents in each state are equal. For p=p_c, the average magnetization (the difference in the density of agents in the two states) is conserved and the system obeys classical voter model dynamics. In one dimension and within a Kirkwood decoupling scheme, the final magnetization in a finite-length system has a non-trivial dependence on the initial magnetization for all p.ne.p_c, in agreement with numerical results. At p_c, the exact 2-spin correlation functions decay algebraically toward the value 1 and the system coarsens as in the classical voter model.Comment: 11 pages, 3 figures, revtex4 2-column format; minor revisions for publication in PR

Spatial interactions in agent-based modeling

Agent Based Modeling (ABM) has become a widespread approach to model complex interactions. In this chapter after briefly summarizing some features of ABM the different approaches in modeling spatial interactions are discussed. It is stressed that agents can interact either indirectly through a shared environment and/or directly with each other. In such an approach, higher-order variables such as commodity prices, population dynamics or even institutions, are not exogenously specified but instead are seen as the results of interactions. It is highlighted in the chapter that the understanding of patterns emerging from such spatial interaction between agents is a key problem as much as their description through analytical or simulation means. The chapter reviews different approaches for modeling agents' behavior, taking into account either explicit spatial (lattice based) structures or networks. Some emphasis is placed on recent ABM as applied to the description of the dynamics of the geographical distribution of economic activities, - out of equilibrium. The Eurace@Unibi Model, an agent-based macroeconomic model with spatial structure, is used to illustrate the potential of such an approach for spatial policy analysis.Comment: 26 pages, 5 figures, 105 references; a chapter prepared for the book "Complexity and Geographical Economics - Topics and Tools", P. Commendatore, S.S. Kayam and I. Kubin, Eds. (Springer, in press, 2014

Meta-stability and microstructure of the LaFe_0.65Co_0.3Pd_0.05O₃ perovskite compound prepared by a modified citrate route

In this paper we report the synthesis and analysis of lanthanum based perovskites substituted with Pd by employing a modified citrate route. Crystallization and phase sequences of the LaFe0.65Co0.3-xPdxO3 (x = 0, 0.05) perovskite(s) are analyzed by means of powder XRD and Rietveld refinement. Regarding the crystal phase development at the LaFe0.65Co0.3Pd0.05O3 perovskite a meta-stable structure can be postulated at temperatures up to 700 °C. Since no PdO species were detected up to the calcination temperature of 700 °C we can conclude that Palladium ions are successfully incorporated into the B-site of the crystal structure of the perovskite. Reduction of the LaFe0.65Co0.3Pd0.05O3 perovskite at 600 °C under 5 vol.% H2 in N2 which was precalcined at 700 °C causes segregation of palladium to form metallic particles with sizes between 10 and 15 nm. Reversible Pd ions reincorporation into the crystal lattice of the LaFe0.65Co0.3Pd0.05O3-700 °C perovskite can be concluded since no PdO was detected after re-oxidation at 600 °C