Evolution of Cooperation when Feedback to Reputation Scores is Voluntary

Reputation systems are used to facilitate interaction between strangers in one-shot social dilemmas, like transactions in e-commerce. The functioning of various reputation systems depend on voluntary feedback derived from the participants in those social dilemmas. In this paper a model is presented under which frequencies of providing feedback to positive and negative experiences in reputation systems explain observed levels of cooperation. The results from simulations show that it is not likely that reputation scores alone will lead to high levels of cooperation.Trust, Reputation, One-Shot Prisoner Dilemma, Voluntary Feedback, Symbols

Short wavelength radio observations of Saturn's rings

Passive radio observations are discussed from 1 mm to 2 cm wavelengths. The interferometric technique was used to observe the brightness of the rings. The reflectivity and disk temperature are also considered. The differences between radio and radar observations are examined and discussed

Understanding Artificial Anasazi

A replication and analysis of the Artificial Anasazi model is presented. It is shown that the success of replicating historical data is based on two parameters that adjust the carrying capacity of the Long House Valley. Compared to population estimates equal to the carrying capacity the specific agent behavior contributes only a modest improvement of the model to fit the archaeological records.Replication, Model Analysis, Model-Based Archaeology, Population Dynamics, Social-Ecological Systems

Bargmann transform, Zak transform, and coherent states

It is well known that completeness properties of sets of coherent states associated with lattices in the phase plane can be proved by using the Bargmann representation or by using the kq representation which was introduced by J. Zak. In this paper both methods are considered, in particular, in connection with expansions of generalized functions in what are called Gabor series. The setting consists of two spaces of generalized functions (tempered distributions and elements of the class S*) which appear in a natural way in the context of the Bargmann transform. Also, a thorough mathematical investigation of the Zak transform is given. This paper contains many comments and complements on existing literature; in particular, connections with the theory of interpolation of entire functions over the Gaussian integers are given

Characterization and computation of canonical tight windows for Gabor frames

Let $(g_{nm})_{n,m\in Z}$ be a Gabor frame for $L_2(R)$ for given window $g$. We show that the window $h^0=S^{-1/2} g$ that generates the canonically associated tight Gabor frame minimizes $\|g-h\|$ among all windows $h$ generating a normalized tight Gabor frame. We present and prove versions of this result in the time domain, the frequency domain, the time-frequency domain, and the Zak transform domain, where in each domain the canonical $h^0$ is expressed using functional calculus for Gabor frame operators. Furthermore, we derive a Wiener-Levy type theorem for rationally oversampled Gabor frames. Finally, a Newton-type method for a fast numerical calculation of \ho is presented. We analyze the convergence behavior of this method and demonstrate the efficiency of the proposed algorithm by some numerical examples

Monte Carlo simulations of the classical two-dimensional discrete frustrated ϕ4\phi ^4 model

The classical two-dimensional discrete frustrated $\phi ^4$ model is studied by Monte Carlo simulations. The correlation function is obtained for two values of a parameter $d$ that determines the frustration in the model. The ground state is a ferro-phase for $d=-0.35$ and a commensurate phase with period N=6 for $d=-0.45$. Mean field predicts that at higher temperature the system enters a para-phase via an incommensurate state, in both cases. Monte Carlo data for $d=-0.45$ show two phase transitions with a floating-incommensurate phase between them. The phase transition at higher temperature is of the Kosterlitz-Thouless type. Analysis of the data for $d=-0.35$ shows only a single phase transition between the floating-fluid phase and the ferro-phase within the numerical error.Comment: 5 figures, submitted to the European Physical Journal

On Bundling in Insurance Markets

This paper analyzes the welfare consequences of bundling different risks in one insurance contract in markets where adverse selection is important. This question is addressed in the context of a competitive insurance model a la Rothschild and Stiglitz (1976) with two sources of risk. Accordingly, there are four possible types of individuals and many incentive compatibility constraints to be considered. We show that the effect of bundling on these incentive compatibility constraints is such that bundling always yields a welfare improvement, and this result only holds when all four types have strictly positive shares in the population. Due to the competition between insurance companies, these benefits accrue to consumers who potentially have fewer contracts to choose from, but benefit from the better sorting possibilities due to bundling.