Evolutionary computation in dynamic and uncertain environments

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Editorial to special issue on evolutionary computation in dynamic and uncertain environments

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Collusion with private and aggregate information

This paper considers three linear asymmetric oligopoly models with (i) a representative consumer, (ii) horizontal differentiation and (iii) vertical differentiation. We show that firms could maximize the joint-profit only based on private and aggregate information. They can choose the “correct“ colluding prices without knowing the demand or profit function. The collusive outcome is a natural focal point despite firms are asymmetric. Collusion can be incentive compatible even though individual actions (prices) are not observed. -- Der Beitrag untersucht drei linear asymmetrische Oligopol-Modelle mit (i) einem repräsentativen Verbraucher, (ii) horizontaler Differenzierung und (iii) vertikaler Differenzierung. Es wird gezeigt, daß Firmen in der Lage sind, den Gesamtprofit allein auf der Grundlage privater und gemeinschaftlicher Information zu maximieren. Sie können zur „richtigen“ Absprache des Preises gelangen, ohne die Nachfrage- oder Gewinn-Funktion zu kennen. Die Absprache stellt einen natürlichen Gleichgewichtspunkt dar, ungeachtet asymmetrischer Verhältnisse. Die Absprache kann anreizkompatibel sein, auch wenn individuelle Aktionen (Preise) nicht beobachtet werden.

Incentives and welfare effect of sharing firm-specific information

This paper studies the incentives and the welfare effect of sharing firm-specific information in asymmetric Cournot and Bertrand oligopoly with mixed substitute and complement goods. Revealing firm-specific cost information is the dominant strategy in Cournot oligopoly, while concealing is so in Bertrand oligopoly. Such information sharing always hurts consumers. It increases social welfare in quantity competition and reduces social welfare in price competition. The results of sharing firm-specific cost information in Cournot oligopoly also apply to sharing firm-specific demand information in Cournot and Bertrand competition. -- In diesem Beitrag werden Anreize und Wohlfahrtseffekte des Austauschs von unternehmensspezifischer Information in einem asymmetrischen Cournot- und Bertrand- Oligopol mit einer Mischung von substitutiven und komplementären Gütern untersucht. Das Aufdecken unternehmensspezifischer Kosteninformation ist die dominante Strategie im Cournot-Oligopol, während im Bertrand-Oligopol diese Information vorenthalten wird. Derartiger Informationsaustausch geht immer zu Lasten der Konsumenten. Er erhöht die soziale Wohlfahrt im Mengenwettbewerb und verringert die soziale Wohlfahrt im Preiswettbewerb. Das Ergebnis des Austauschs unternehmensspezifischer Kosteninformation im Cournot-Oligopol läßt sich auch auf den unternehmensspezifischen Austausch von Nachfrageinformation im Cournot- und Bertrand-Wettbewerb anwenden.

Bounded perturbation resilience of projected scaled gradient methods

We investigate projected scaled gradient (PSG) methods for convex minimization problems. These methods perform a descent step along a diagonally scaled gradient direction followed by a feasibility regaining step via orthogonal projection onto the constraint set. This constitutes a generalized algorithmic structure that encompasses as special cases the gradient projection method, the projected Newton method, the projected Landweber-type methods and the generalized Expectation-Maximization (EM)-type methods. We prove the convergence of the PSG methods in the presence of bounded perturbations. This resilience to bounded perturbations is relevant to the ability to apply the recently developed superiorization methodology to PSG methods, in particular to the EM algorithm.Comment: Computational Optimization and Applications, accepted for publicatio

Conformal or Walking? Monte Carlo renormalization group studies of SU(3) gauge models with fundamental fermions

Strongly coupled gauge systems with many fermions are important in many phenomenological models. I use the 2-lattice matching Monte Carlo renormalization group method to study the fixed point structure and critical indexes of SU(3) gauge models with 8 and 12 flavors of fundamental fermions. With an improved renormalization group block transformation I am able to connect the perturbative and confining regimes of the N_f=8 flavor system, thus verifying its QCD-like nature. With N_f=12 flavors the data favor the existence of an infrared fixed point and conformal phase, though the results are also consistent with very slow walking. I measure the anomalous mass dimension in both systems at several gauge couplings and find that they are barely different from the free field value.Comment: 26 pages, 11 figure