51 citations · 242 across the 22 of their papers we have counts for
24 papers
Optimality Despite Chaos in Fee Markets
Stefanos Leonardos, Daniël Reijsbergen, Barnabé Monnot +1
Transaction fee markets are essential components of blockchain economies, as they resolve the inherent scarcity in the number of transactions that can be added to each block. In ea…
Transaction Fees on a Honeymoon: Ethereum's EIP-1559 One Month Later
Daniël Reijsbergen, Shyam Sridhar, Barnabé Monnot +3
Ethereum Improvement Proposal (EIP) 1559 was recently implemented to transform Ethereum's transaction fee market. EIP-1559 utilizes an algorithmic update rule with a constant learn…
Exploration-Exploitation in Multi-Agent Competition: Convergence with Bounded Rationality
Stefanos Leonardos, Georgios Piliouras, Kelly Spendlove
The interplay between exploration and exploitation in competitive multi-agent learning is still far from being well understood. Motivated by this, we study smooth Q-learning, a pro…
From Griefing to Stability in Blockchain Mining Economies
Yun Kuen Cheung, Stefanos Leonardos, Georgios Piliouras +1
We study a game-theoretic model of blockchain mining economies and show that griefing, a practice according to which participants harm other participants at some lesser cost to the…
Global Convergence of Multi-Agent Policy Gradient in Markov Potential Games
Stefanos Leonardos, Will Overman, Ioannis Panageas +1
Potential games are arguably one of the most important and widely studied classes of normal form games. They define the archetypal setting of multi-agent coordination as all agent…
Learning in Markets: Greed Leads to Chaos but Following the Price is Right
Yun Kuen Cheung, Stefanos Leonardos, Georgios Piliouras
We study learning dynamics in distributed production economies such as blockchain mining, peer-to-peer file sharing and crowdsourcing. These economies can be modelled as multi-prod…
Dynamical Analysis of the EIP-1559 Ethereum Fee Market
Stefanos Leonardos, Barnabé Monnot, Daniël Reijsbergen +2
Participation in permissionless blockchains results in competition over system resources, which needs to be controlled with fees. Ethereum's current fee mechanism is implemented vi…
Exploration-Exploitation in Multi-Agent Learning: Catastrophe Theory Meets Game Theory
Stefanos Leonardos, Georgios Piliouras
Exploration-exploitation is a powerful and practical tool in multi-agent learning (MAL), however, its effects are far from understood. To make progress in this direction, we study…
Exploring the Predictability of Cryptocurrencies via Bayesian Hidden Markov Models
Constandina Koki, Stefanos Leonardos, Georgios Piliouras
In this paper, we consider a variety of multi-state Hidden Markov models for predicting and explaining the Bitcoin, Ether and Ripple returns in the presence of state (regime) dynam…
Catastrophe by Design in Population Games: Destabilizing Wasteful Locked-in Technologies
Stefanos Leonardos, Iosif Sakos, Costas Courcoubetis +1
In multi-agent environments in which coordination is desirable, the history of play often causes lock-in at sub-optimal outcomes. Notoriously, technologies with a significant envir…
A Peek into the Unobservable: Hidden States and Bayesian Inference for the Bitcoin and Ether Price Series
Constandina Koki, Stefanos Leonardos, Georgios Piliouras
Conventional financial models fail to explain the economic and monetary properties of cryptocurrencies due to the latter's dual nature: their usage as financial assets on the one s…
Strategic customer behavior in a queueing system with alternating information structure
Yiannis Dimitrakopoulos, Antonis Economou, Stefanos Leonardos
Strategic customer behavior is strongly influenced by the level of information that is provided to customers. Hence, to optimize the design of queueing systems, many studies consid…
PREStO: A Systematic Framework for Blockchain Consensus Protocols
Stefanos Leonardos, Daniel Reijsbergen, Georgios Piliouras
The rapid evolution of blockchain technology has brought together stakeholders from fundamentally different backgrounds. The result is a diverse ecosystem, as exemplified by the de…
On the Equilibrium Uniqueness in Cournot Competition with Demand Uncertainty
Stefanos Leonardos, Costis Melolidakis
We revisit the linear Cournot model with uncertain demand that is studied in Lagerlöf (2006)* and provide sufficient conditions for equilibrium uniqueness that complement the exist…
On the Mean Residual Life of Cantor-Type Distributions: Properties and Economic Applications
Stefanos Leonardos, Costis Melolidakis
In this paper, we consider the mean residual life (MRL) function of the Cantor distribution and study its properties. We show that the MRL function is continuous at all points, loc…
Oceanic Games: Centralization Risks and Incentives in Blockchain Mining
Nikos Leonardos, Stefanos Leonardos, Georgios Piliouras
To participate in the distributed consensus of permissionless blockchains, prospective nodes -- or miners -- provide proof of designated, costly resources. However, in contrast to…
Weighted Voting on the Blockchain: Improving Consensus in Proof of Stake Protocols
Stefanos Leonardos, Daniel Reijsbergen, Georgios Piliouras
Proof of Stake (PoS) protocols rely on voting mechanisms to reach consensus on the current state. If an enhanced majority of staking nodes, also called validators, agree on a propo…
Incentives in Ethereum's Hybrid Casper Protocol
Vitalik Buterin, Daniel Reijsbergen, Stefanos Leonardos +1
We present an overview of hybrid Casper the Friendly Finality Gadget (FFG): a Proof-of-Stake checkpointing protocol overlaid onto Ethereum's Proof-of-Work blockchain. We describe i…
Measuring Market Performance with Stochastic Demand: Price of Anarchy and Price of Uncertainty
Costis Melolidakis, Stefanos Leonardos, Constandina Koki
Globally operating suppliers face the rising challenge of wholesale pricing under scarce data about retail demand, in contrast to better informed, locally operating retailers. At t…
A Class of Distributions for Linear Demand Markets
Stefanos Leonardos, Costis Melolidakis
In this paper, we study distributions that describe markets with linear stochastic demand. We express the price elasticity of expected demand in terms of the mean residual demand (…
Comparative Statics via Stochastic Orderings in a Two-Echelon Market with Upstream Demand Uncertainty
Constandina Koki, Stefanos Leonardos, Costis Melolidakis
We revisit the classic Cournot model and extend it to a two-echelon supply chain with an upstream supplier who operates under demand uncertainty and multiple downstream retailers w…
Monopoly Pricing in Vertical Markets with Demand Uncertainty
Stefanos Leonardos, Costis Melolidakis, Constandina Koki
Pricing decisions are often made when market information is still poor. In turn, existing theoretical models often reason about the response of optimal prices to changing market ch…
On the commitment value and commitment optimal strategies in bimatrix games
Stefanos Leonardos, Costis Melolidakis
Given a bimatrix game, the associated leadership or commitment games are defined as the games at which one player, the leader, commits to a (possibly mixed) strategy and the other…
Endogenizing the Cost Parameter in Cournot Oligopoly
Stefanos Leonardos, Costis Melolidakis
We study the effects of endogenous cost formation in the classic Cournot oligopoly through an extended two-stage game. The competing Cournot firms produce low-cost but limited quan…