Philipp Zahn | Research
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Research Overview


My research focuses on merging computational and economic perspectives. As economic decisions are more and more mediated through software, we need to understand the economic consequences of interacting computations. This is particularly important, if we want to design new institutions.

I have been working on compositional game theory which provides a new mathematical foundation for game theory blending game theory and computations. On the basis of that theory, we have developed a software engine which allows to represent and analyze games (see here for more information and here for a tutorial how to use it). There are various applications of this framework, including the design of smart contracts as well protocol designs for blockchains. We have received a grant by the Ethereum foundation supporting the development of the software.

More recently, I have also started applying the framework to strategic decision-making of learning agents. One immediate application is the autonomous price-setting by companies using reinforcement learning. A question that naturally arise in such settings is whether autonomous pricing systems may lead to collusive behavior; whether dominant companies can leverage such system to further their dominance etc.

Lastly, I have worked on decision processes of individual agents in online settings. Such environments are intentionally designed and provide information as well as support functionality (filtering, sorting) for agents. The question is how agents are influenced by such environments and how they may even be able to leverage them for effective decision-making.


Working papers


Robust Algorithmic Collusion [ArXiv]

(joint with Nicolas Eschenbaum and Filip Mellgren)


Composing Games into Complex Institutions [ArXiv] 

(joint with Seth Frey, Jules Hedges, and Joshua Tan)


Sequential Games and Non-Deterministic Selection Functions [ArXiv] 

(joint with Joe Bolt and Jules Hedges)


Sorting and Filtering as Effective Rational Choice Procedures [ArXiv]

(joint with Paulo Oliva)


Compositionality and string diagrams for Game Theory  [ArXiv]

(joint with Jules Hedges, Evguenia Winschel, Viktor Winschel)



Bayesian Open Games [ArXiv] 

(joint with Joe Bolt and Jules Hedges) accepted for publication at Compositionality 2021


On Rational Choice and the Representation of Decision Problems [ArXiv]

(joint with Paulo Oliva) accepted for publication at Games 2021


Compositional Game Theory [ArXiv]

(joint with Neil Ghani, Jules Hedges, Viktor Winschel) Proceedings of Logic in Computer Science (LiCS) 2018


Higher-Order Decision Theory [ArXiv]

(joint with Jules Hedges, Paulo Oliva, Evguenia Winschel, Viktor Winschel) Lecture Notes in Computer Science, Algorithmic Decision Theory, 2017


Selection Equilibria of Higher-Order Games  [ArXiv]

(joint with Jules Hedges, Paulo Oliva, Evguenia Winschel, Viktor Winschel) Lecture Notes in Computer Science, PADL, 2017


Contextuality and the Weak Axiom in the Theory of Choice [ArXiv]

(joint with William Zeng) Lecture Notes in Computer Science, Quantum Interaction, 2015


Public Economics

Minimum Prices and Social Interactions: Evidence from the German Renewable Energy Program [SSRN]

Energy Economics, 2019

(joint with Justus Inhoffen and Christoph Siemroth)


Social Preferences, Public Policy, and Gender in “Social Economics, edited by Joan Costa-Font and Mario Macis, MIT Press, CESIfo seminar series, 2017

(joint with Evguenia Winschel)


Incentives and Group Identity Games and Economic Behavior 2014

(joint with Paolo Masella and Stephan Meier)


Political Support in Hard Times: Do People Care about National Welfare? European Journal of Political Economy, 2014

(joint with Jana Friedrichsen)


Employment and Unemployment of the Elderly: A Microeconometric Evaluation of the Reform of the Unemployment Compensation System in 1997

(in German)  Journal of Economics and Statistics, Bd. 227, Vol. 1, S. 65-86, Stuttgart 2007 ( joint with Eva Mueller and Ralf Wilke )

Non-technical essays


What Problem Does Compositional Game Theory Solve? [link]


Games as Computations or Computations as Games? [link]


Code as Theory [link]


Mechanisms for the Provision of Public Goods in the Digital Age [SSRN]


Blockchain and Ex-Ante Exclusion Mechanisms [SSRN]