Achieving EF1 and Epistemic EFX Guarantees Simultaneously

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Hauptverfasser: Akrami, Hannaneh, Mahara, Ryoga, Mehlhorn, Kurt, Rathi, Nidhi
Format: Preprint
Veröffentlicht: 2026
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author Akrami, Hannaneh
Mahara, Ryoga
Mehlhorn, Kurt
Rathi, Nidhi
author_facet Akrami, Hannaneh
Mahara, Ryoga
Mehlhorn, Kurt
Rathi, Nidhi
contents We study the fundamental problem of fairly dividing a set of indivisible goods among agents with additive valuations. Here, envy-freeness up to any good (EFX) is a central fairness notion and resolving its existence is regarded as one of the most important open problems in this area of research. Two prominent relaxations of EFX are envy-freeness up to one good (EF1) and epistemic EFX (EEFX). While allocations satisfying each of these notions individually are known to exist even for general monotone valuations, whether both can be satisfied simultaneously remains open for all instances in which the EFX problem is itself unresolved. In this work, we show that there always exists an allocation that is both EF1 (in fact, the stronger notion EFL) and EEFX for additive valuations, thereby resolving the primary open question raised by Akrami and Rathi (2025) and bringing us one step closer to resolving the elusive EFX problem. We introduce a new share-based fairness notion, termed strong EEFX share, which may be of independent interest and which implies EEFX feasibility of bundles. We show that this notion is compatible with EF1, leading to the desired existence result.
format Preprint
id arxiv_https___arxiv_org_abs_2602_11732
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Achieving EF1 and Epistemic EFX Guarantees Simultaneously
Akrami, Hannaneh
Mahara, Ryoga
Mehlhorn, Kurt
Rathi, Nidhi
Computer Science and Game Theory
We study the fundamental problem of fairly dividing a set of indivisible goods among agents with additive valuations. Here, envy-freeness up to any good (EFX) is a central fairness notion and resolving its existence is regarded as one of the most important open problems in this area of research. Two prominent relaxations of EFX are envy-freeness up to one good (EF1) and epistemic EFX (EEFX). While allocations satisfying each of these notions individually are known to exist even for general monotone valuations, whether both can be satisfied simultaneously remains open for all instances in which the EFX problem is itself unresolved. In this work, we show that there always exists an allocation that is both EF1 (in fact, the stronger notion EFL) and EEFX for additive valuations, thereby resolving the primary open question raised by Akrami and Rathi (2025) and bringing us one step closer to resolving the elusive EFX problem. We introduce a new share-based fairness notion, termed strong EEFX share, which may be of independent interest and which implies EEFX feasibility of bundles. We show that this notion is compatible with EF1, leading to the desired existence result.
title Achieving EF1 and Epistemic EFX Guarantees Simultaneously
topic Computer Science and Game Theory
url https://arxiv.org/abs/2602.11732