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Documents authored by Poças, Diogo

Document
DOI: 10.4230/LIPIcs.AFT.2026.17
Belief-Aware Pivotal Mechanism for DAO Committees

Authors: Nuno Braz, Diogo Poças, and Miguel Correia

Published in: LIPIcs, Volume 395, 8th Conference on Advances in Financial Technologies (AFT 2026)

Abstract
Decentralized Autonomous Organizations (DAOs) increasingly delegate decisions to small committees whose members hold two independent kinds of private information: idiosyncratic preferences over alternatives (what they want) and beliefs about which alternative best serves the organization (what they know). Members have no reason to reveal what they know unless they are incentivized to do so. Standard voting rules are designed to extract only what members want. If these two pieces of information are not aligned, the organization can end up making a suboptimal decision. Existing mechanisms for eliciting (extracting) beliefs from experts, such as Decision Scoring Rules and Decision Markets, face well-known impossibility results in multi-agent settings under deterministic decision rules, and ignore the fact that agents can have idiosyncratic preferences over alternatives. This paper proposes a mechanism for binary committee decisions that augments the pivotal mechanism, an instance of the Groves mechanism, with a reward that depends on the outcome distributed after a boolean signal, indicating success or failure of the outcome, is observed. The mechanism aggregates the experts' private information to maximize the probability that its decision agrees with a weighted linear pooling of the experts' beliefs, framing the designer’s problem as classification rather than welfare maximization. An affine family of reward rules is proposed, and the region of parameters that simultaneously satisfy dominant-strategy incentive compatibility, interim individual rationality, and budget feasibility is derived. In informative-belief environments, the mechanism outperforms majority voting, including majority voting augmented with the same outcome-contingent rewards, especially when the committee’s average preferences are biased against the superior alternative.
Cite as

Nuno Braz, Diogo Poças, and Miguel Correia. Belief-Aware Pivotal Mechanism for DAO Committees. In 8th Conference on Advances in Financial Technologies (AFT 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 395, pp. 17:1-17:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{braz_et_al:LIPIcs.AFT.2026.17,
  author =	{Braz, Nuno and Po\c{c}as, Diogo and Correia, Miguel},
  title =	{{Belief-Aware Pivotal Mechanism for DAO Committees}},
  booktitle =	{8th Conference on Advances in Financial Technologies (AFT 2026)},
  pages =	{17:1--17:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-451-2},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{395},
  editor =	{Kiayias, Aggelos and Kyropoulou, Maria},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.AFT.2026.17},
  URN =		{urn:nbn:de:0030-drops-278712},
  doi =		{10.4230/LIPIcs.AFT.2026.17},
  annote =	{Keywords: Mechanism Design, Decentralized Autonomous Organizations, Committees, Information Aggregation}
}
Document
Track A: Algorithms, Complexity and Games
DOI: 10.4230/LIPIcs.ICALP.2020.32
Existence and Complexity of Approximate Equilibria in Weighted Congestion Games

Authors: George Christodoulou, Martin Gairing, Yiannis Giannakopoulos, Diogo Poças, and Clara Waldmann

Published in: LIPIcs, Volume 168, 47th International Colloquium on Automata, Languages, and Programming (ICALP 2020)

Abstract
We study the existence of approximate pure Nash equilibria (α-PNE) in weighted atomic congestion games with polynomial cost functions of maximum degree d. Previously it was known that d-approximate equilibria always exist, while nonexistence was established only for small constants, namely for 1.153-PNE. We improve significantly upon this gap, proving that such games in general do not have Θ̃(√d)-approximate PNE, which provides the first super-constant lower bound. Furthermore, we provide a black-box gap-introducing method of combining such nonexistence results with a specific circuit gadget, in order to derive NP-completeness of the decision version of the problem. In particular, deploying this technique we are able to show that deciding whether a weighted congestion game has an Õ(√d)-PNE is NP-complete. Previous hardness results were known only for the special case of exact equilibria and arbitrary cost functions. The circuit gadget is of independent interest and it allows us to also prove hardness for a variety of problems related to the complexity of PNE in congestion games. For example, we demonstrate that the question of existence of α-PNE in which a certain set of players plays a specific strategy profile is NP-hard for any α < 3^(d/2), even for unweighted congestion games. Finally, we study the existence of approximate equilibria in weighted congestion games with general (nondecreasing) costs, as a function of the number of players n. We show that n-PNE always exist, matched by an almost tight nonexistence bound of Θ̃(n) which we can again transform into an NP-completeness proof for the decision problem.
Cite as

George Christodoulou, Martin Gairing, Yiannis Giannakopoulos, Diogo Poças, and Clara Waldmann. Existence and Complexity of Approximate Equilibria in Weighted Congestion Games. In 47th International Colloquium on Automata, Languages, and Programming (ICALP 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 168, pp. 32:1-32:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{christodoulou_et_al:LIPIcs.ICALP.2020.32,
  author =	{Christodoulou, George and Gairing, Martin and Giannakopoulos, Yiannis and Po\c{c}as, Diogo and Waldmann, Clara},
  title =	{{Existence and Complexity of Approximate Equilibria in Weighted Congestion Games}},
  booktitle =	{47th International Colloquium on Automata, Languages, and Programming (ICALP 2020)},
  pages =	{32:1--32:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-138-2},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{168},
  editor =	{Czumaj, Artur and Dawar, Anuj and Merelli, Emanuela},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2020.32},
  URN =		{urn:nbn:de:0030-drops-124392},
  doi =		{10.4230/LIPIcs.ICALP.2020.32},
  annote =	{Keywords: Atomic congestion games, existence of equilibria, pure Nash equilibria, approximate equilibria, hardness of equilibria}
}

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