Decentralization has an important geographic dimension that conventional metrics, such as stake distribution, often overlook. Validator location affects resilience to regional shocks (e.g., outages, natural disasters, or government intervention) as well as fairness in reward access. Yet major blockchain protocols do not encode geographical location in their rules; instead, validator locations emerge from a combination of economic incentives, regulatory constraints, infrastructure availability, and validator deployment choices. When some locations offer systematic advantages, validators may strategically co-locate to increase expected rewards, as in Ethereum, where validators cluster along the Atlantic corridor, which exhibits favorable latency. In this paper, we develop a formal model of validators' geographical positioning incentives under Ethereum's protocol design, capturing the interaction between its two block-building paradigms, local and external block building, and the distribution of validators and information sources. We analyze the model under a mean-field approximation and complement it with agent-based simulations calibrated with real-world latency data to quantify how these incentives translate into geographical concentration under heterogeneous geographic and infrastructural conditions. Our results show that Ethereum's block-building architecture is not geographically neutral. Both paradigms create location-dependent payoffs and incentives to move closer to payoff-relevant parties to reduce propagation delays, though through different mechanisms. Asymmetric access to information sources further increases geographical centralization. We also show that consensus parameters, including attestation thresholds and slot times, affect latency sensitivity and can strengthen these effects. Finally, we discuss implications for protocol design and possible mitigation directions.

翻译：去中心化具有传统指标（如权益分布）常忽视的重要地理维度。验证者位置影响对区域性冲击（如断电、自然灾害或政府干预）的韧性，以及奖励获取的公平性。然而，主流区块链协议并未在其规则中编码地理位置；相反，验证者位置由经济激励、监管约束、基础设施可用性和验证者部署选择共同决定。当某些位置具备系统性优势时，验证者可能会战略性地聚集以增加预期奖励——例如在以太坊中，验证者们沿着具有低延迟优势的大西洋走廊形成集群。本文提出一个形式化模型，用以描述以太坊协议设计下验证者的地理定位激励，捕捉其两种区块构建范式（本地构建与外部构建）与验证者及信息源分布之间的交互作用。我们通过平均场近似分析该模型，并辅以基于真实世界延迟数据校准的智能体模拟，量化在不同地理与基础设施条件下这些激励如何转化为地理集中度。研究结果表明，以太坊的区块构建架构并非地理中性。两种范式均产生与位置相关的收益，并通过不同机制激励验证者向收益相关方靠近以降低传播延迟。信息源的非对称访问进一步加剧了地理集中化。我们还证明，包括认证阈值和时隙时间在内的共识参数会影响延迟敏感性，并可能强化这些效应。最后，我们讨论了对协议设计的启示及可能的缓解方向。