Dominik Klein

Convergence, Continuity and Recurrence in Dynamic Epistemic Logic

The paper analyzes dynamic epistemic logic from a topological perspective. The main contribution consists of a framework in which dynamic epistemic logic satisfies the requirements for being a topological dynamical system thus interfacing discrete dynamic logics with continuous mappings of dynamical systems. The setting is based on a notion of logical convergence, demonstratively equivalent with convergence in Stone topology. Presented is a flexible, parametrized family of metrics inducing the latter, used as an analytical aid. We show maps induced by action model transformations continuous with respect to the Stone topology and present results on the recurrent behavior of said maps.

Introspection, Normality and Agglomeration

This paper explores a non-normal logic of beliefs for boundedly rational agents. The logic we study stems from the epistemic-doxastic system developed by Stalnaker [1]. In that system, if knowledge is not positively introspective then beliefs are not closed under conjunction. They are, however, required to be pairwise consistent, a requirement that has been called agglomerativity elsewhere. While bounded agglomerativity requirements, i.e., joint consistency for every n-tuple of beliefs up to a fixed n, are expressible in that logic, unbounded agglomerativity is not. We study an extension of this logic of beliefs with such an unbounded agglomerativity operator, provide a sound and complete axiomatization for it, show that it has a sequent calculus that enjoys the admissibility of cut, that it has the finite model property, and that it is decidable.

Knowledge, belief, normality, and introspection

We study two logics of knowledge and belief stemming from the work of Stalnaker (2006), omitting positive introspection for knowledge. The two systems are equivalent with positive introspection, but not without. We show that while the logic of beliefs remains unaffected by omitting introspection for knowledge in one system, it brings significant changes to the other. The resulting logic of belief is non-normal, and its complete axiomatization uses an infinite hierarchy of coherence constraints. We conclude by returning to the philosophical interpretation underlying both models of belief, showing that neither is strong enough to support a probabilistic interpretation, nor an interpretation in terms of certainty or the “mental component” of knowledge.

Focusing on Campaigns

One of the important lessons to take away from Rohit Parikh’s impressive body of work is that logicians and computer scientists have much to gain by focusing their attention on the intricacies of political campaigns. Drawing on recent work developing a theory of expressive voting, we study the dynamics of voters’ opinions during an election. In this paper, we develop a model in which the relative importance of the different issues that concern a voter may change either in response to candidates’ statements during a campaign or due to unforeseen events. We study how changes in a voter?s attention to the issues influence voting behavior under voting systems such as plurality rule and approval voting. We argue that it can be worthwhile for candidates to reshape public focus, but that doing so can be a complex and risky activity.

Rationality in context

The emergence of economic inequality has often been linked to individual differences in mental or physical capacities. By means of an agent-based simulation this paper shows that neither of these is a necessary condition. Rather, inequality can arise from iterated interactions of fully rational agents. This bears consequences for our understanding of both inequality and rationality. In a setting of iterated bargaining games, we claim that expected utility maximizing agents perform suboptimally in comparison with other strategies. The reason for this lies in complex feedback effects between an agents’ action and the quality of beliefs used to calculate expected utility. Consequentially, we argue that the standard notion of rationality as maximizing expected utility is insufficient, even for certain standard cases of economic interaction.

Generalized Trust in the Mirror: An Agent-Based Model on the Dynamics of Trust

»Gesellschaftliches Vertrauen in Reflektion. Eine agentenbasierte Modellierung von Vertrauensdynamiken.« High levels of trust have been linked to a variety of benefits including the well-functioning of markets and political institutions or the ability of societies to solve public goods problems endogenously. While there is extensive literature on the macro-level determinants of trust, the micro-level processes underlying the emergence and stability of trust are not yet sufficiently understood. We address this lacuna by means of a computer model. In this paper, conditions under which trust is likely to emerge and be sustained are identified. We focus our analysis mainly on the individual characteristics of agents: their social or geographical mobility, their attitude towards others or their general uncertainty about the environment. Contrary to predictions from previous literature, we show that immobile agents are detrimental to both, the emergence and robustness of trust. Additionally, we identify a hidden link between trusting others and being trustworthy.

Wenn Du gehst, geh ich auch! : Die Rolle von Informationskaskaden bei der Entstehung von Massenbewegungen

Should I Stay Or Should I Go? The Influence of Informational Cascades in the Emergence of Mass Movements Abstract: This paper studies the epistemic dynamics preceding the emergence of mass movements. By means of an agent-based simulation, we study the informational processes generating those shared attitudes towards a political system that are necessary for mass movements. We show that societies of lower mobility will structurally underestimate the potential for political change. Moreover, we find systematic differences in attitudes between critics and supporters of a regime. A side-effect of the emergent informational dynamics is that system critics will, over time, develop higher estimates of the potential for change than their less discontent peers.

Logic and Ethics : An Integrated Model for Norms, Intentions and Actions

The paper investigates the way norms relate to and affect agents’ intentions and actions. Current work in deontic logic dealing with agency mainly falls within two different groups: a variety of frameworks which adopt a purely external approach and represent agency in terms of possible outcomes of actions, and frameworks which instead endorse an internal approach and focus exclusively on the agent’s intentions. The paper argues that neither of these models alone can produce a satisfactory analysis. An integrated model which combines the internal and external approaches is therefore put forward. The model is dynamic and represents the change that accepting a goal norm triggers in an agent’s intentions (especially the so-called “prior-intentions”) and actions.