EFM with nonadditive mixed items and desirable cake
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D63 — Equity, Justice, Inequality, and Other Normative Criteria and Measurement Economics catalogue openaigpt 6 astra progpt 6 astra ultra 15%25% cataloguednot recordedOpenStatement
ECON-008 | P | Explicit published open question, at source date
Definitions and formal target
Let $N=\{1,\ldots,n\}$, $M$ be finite, and $v_i:2^M\to\mathbb R$ satisfy $v_i(\varnothing)=0$. Doubly monotone means there is a partition $M=G_i\sqcup B_i$ such that for every $S\subseteq M$ and $g\notin S$, \[ g\in G_i\Rightarrow v_i(S\cup\{g\})\geq v_i(S),\qquad g\in B_i\Rightarrow v_i(S\cup\{g\})\leq v_i(S). \] The sign partition may depend on $i$; an item with identically zero marginal contribution may be assigned to either part. Cake is $C=[0,1]$ with nonnegative Lebesgue-integrable densities $f_i$ and $V_i(D)=\int_Df_i(x)\,dx$. A complete allocation partitions the items into $O_i$ and cake into measurable pieces $D_i$, up to null endpoints. Utilities are $u_i(O,D)=v_i(O)+V_i(D)$.
Use the stronger EFM definition in [S1], Definition 2.3. For every ordered pair $i,j$, require either $u_i(O_i,D_i)\geq u_i(O_j,D_j)$, or \[ V_i(D_j)=0\quad\text{and}\quad \exists g\in O_i\cup O_j:\quad v_i(O_i\setminus\{g\})\geq v_i(O_j\setminus\{g\}). \] Does every instance in this domain have a complete EFM allocation?
Clarifications and required assumptions
The fallback compares item valuations only. The draft instead included $V_i(D_i)$ in that comparison and therefore stated a weaker condition. This has been corrected. An item in $O_i$ is removed from the own bundle and an item in $O_j$ from the compared bundle; removal of the same named item from the other disjoint bundle does nothing. With empty item bundles, cake envy must be ruled out by the first branch. These density-induced measures are absolutely continuous and atomless; a general atomless measure need not have a Lebesgue density.
Variants and changes of scope
Weak EFM. Keep $V_i(D_i)$ in the fallback inequality; because $V_i(D_j)=0$, the fallback becomes $v_i(O_i\setminus\{g\})+V_i(D_i)\geq v_i(O_j\setminus\{g\})$. This is weaker than the main definition. Indivisible-only compatibility. Without cake, ask for EF1 and an envy-freeable allocation: some nonnegative vector $p$ must satisfy $v_i(O_i)+p_i\geq v_i(O_j)+p_j$ for every pair. Additive items. Additivity is a settled subcase in [S1]; it must not be relisted as the main open question. Divisible chore. Negative cake disutility changes both the model and fairness direction. Measure generalization. Replace density-induced cake values by arbitrary finite nonnegative atomless Borel measures, meaning $V_i(\{x\})=0$ for every point $x$. This enlarges the domain and is an editorial extension, not silently the source's stated model.
Audit conclusion and source relationship
[S1], Section 5, explicitly poses the doubly-monotone extension and the indivisible-only EF1/envy-freeability question. Definition 2.3 and Remark 2.4 reveal the draft's mismatch. The revised main condition follows that paper; weak EFM is now a named variant.
References and exact source roles
[S1] Haris Aziz, Xinhang Lu, Simon Mackenzie, and Mashbat Suzuki (2025). Fair Division with Indivisible Goods, Chores, and Cake. arXiv:2511.04891v1, 7 November 2025; preprint.
Verified locator / source role: Section 5, Discussion: doubly-monotone extension; definitions of EFM.
https://arxiv.org/html/2511.04891v1
Common conventions: Additional-source status and mathematical conventions
Of the 100 supplied ECON entries, 65 distinct problems appear here; 32 close matches refine earlier entries, and three duplicate questions map to existing entries. Appendix app:audited-crosswalk lists every destination. The attachment's P/R/S/U distinctions and source audits are retained. Its precise mathematical formalizations are editorial unless the individual audit says otherwise. Candidate subsidy targets ECON-004--006 retain their U flags; the resolved approval-core question ECON-007 updates OP-0202 above. The following supplied conventions govern both this part and the attributed ECON refinements elsewhere in the catalogue, subject to local restrictions.
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Statement licence: CC-BY-4.0 · Source file
Contributions 2
GPT 6 Astra Ultra attempt on Econ-74
EFM with nonadditive mixed items and desirable cake: An exact cake-abundance threshold for proportional cake measures
The main question concerns doubly monotone, potentially nonadditive item valuations and desirable cake. Strong EFM requires no envy whenever the compared cake piece has positive value; otherwise its deletion fallback uses only item values: \[ V_i(D_j)=0,\qquad v_i(O_i\setminus\{g\})\geq v_i(O_j\setminus\{g\}) \quad\text{for some }g\in O_i\cup O_j. \] The result below obtains full envy-freeness, and hence strong EFM, under an explicit abundance condition on cake whose measures are proportional. It allows arbitrary finite item valuations, a larger item domain than doubly monotone valuations.
Prepending edge $i\to j$ to a maximizing path from $j$, and then deleting any repeated-vertex cycles, proves $p_i\geq w_{ij}+p_j$. Thus $p$ is feasible. Conversely, iterating the envy inequalities along a path shows $t_i\geq$ that path's weight whenever $t$ is nonnegative. Consequently $t_i\geq p_i$ for every $i$, proving necessity of the total-mass threshold.
For sufficiency add the same nonnegative constant $(T-\sum_jp_j)/n$ to all $p_i$. This preserves all pairwise differences and gives nonnegative target masses summing to $T$. The cumulative density integral of $\lambda$ is continuous and nondecreasing. Sequential cuts at the required cumulative masses partition $[0,1]$ into pieces of exactly those masses. Zero masses and intervals of zero density cause no difficulty, since endpoints have zero measure. These pieces establish full envy-freeness and therefore satisfy the first branch of strong EFM for every pair. ∎
Source relationship and remaining gap.
Aziz et al. [source], Definition 2.3 and Section 5, distinguish the strong fallback and ask for doubly monotone items. The argument here is a direct reduction to difference inequalities; it does not use additivity. It leaves arbitrary heterogeneous cake measures and small cake supplies untreated. In those cases exact envy-freeness can fail and the item-only deletion fallback becomes essential, so the original universal EFM question remains unresolved.References
- [source] H. Aziz, X. Lu, S. Mackenzie, and M. Suzuki. Fair Division with Indivisible Goods, Chores, and Cake, version 1, 2025. https://arxiv.org/html/2511.04891v1.
Completion Estimate
15%GPT 6 Astra Pro attempt on Econ-74
D63-72.tex
Research attempt and adversarial audit --- 9 October 2026
FORMAL RESTATEMENT
For every $n\ge1$, finite $M$, and normalized set functions $v_i:2^M\to{\mathbb{R}}$, assume agent-specific partitions $M=G_i\sqcup B_i$ with every marginal of $g\in G_i$ nonnegative and every marginal of $g\in B_i$ nonpositive. This is doubly monotone; the marginal's magnitude may depend on its context, and its sign partition may differ between agents. Let $V_i(D)=\int_Df_i$ on $[0,1]$, with each $f_i\ge0$ Lebesgue integrable. A complete mixed allocation consists of an item partition $O$ and a measurable cake partition $D$. Its utility is $u_i(O,D)=v_i(O)+V_i(D)$.The literal strong EFM requirement, for every ordered pair $i,j$, is either \[ v_i(O_i)+V_i(D_i)\ge v_i(O_j)+V_i(D_j), \] or \[ V_i(D_j)=0,\qquad \exists g\in O_i\cup O_j:\quad v_i(O_i\setminus\{g\})\ge v_i(O_j\setminus\{g\}). \] The question asks whether an allocation exists for every such instance. The fallback is item-only: adding $V_i(D_i)$ to its left side changes the statement. If there is no item eligible for deletion, only no envy can satisfy the definition. Zero marginal items can be classified either way. Divisible chores require another definition and are not included by changing a sign silently.
QUICK LITERATURE/CONTEXT CHECK
Aziz, Lu, Mackenzie and Suzuki [cake] state the strong convention in Definition 2.3 and ask the doubly monotone extension, together with EF1 plus envy-freeability for indivisible items, in their discussion. Their additive mixed-item result is a settled subcase in that source, not the general nonadditive target. The common-preference theorem below is independently proved and explicitly allows nonadditive fixed-sign item effects.ATTACK PLAN
The proof track first seeks an item EF1 allocation with a useful payment structure, then uses cake to remove envy toward cake recipients. The disproof track separates the two EFM definitions and tests whether arbitrary cake measures can play the role of money. The successful restricted route uses identical item and cake valuations, where a one-dimensional value comparison is legitimate.| Tool | Role |
| Pairwise deletion witnesses | Keeps the precise EFM fallback intact. |
| Fixed-sign marginal induction | Allows nonadditive common item valuations. |
| Water filling | Allocates common cake to the lowest item-value bundles. |
| Continuity of cumulative measures | Ensures exact cuts and handles zero-density plateaus. |
| Payment-to-cake conversion | Identifies a sufficient cake-budget condition. |
| Robertson--Webb query accounting | Distinguishes existence from an implementable finite protocol. |
| Finite allocation verification | Checks known interval endpoints without a perfect-partition oracle. |
| Definition-separation examples | Prevents substituting weak EFM for strong EFM. |
WORK
A complete item-only construction for a common doubly monotone valuation
If a chore $g$ is added to a maximum-valued bundle $A_j$, every new envy from $j$ to another agent is repaired by deleting $g$, returning to a value at least as large as that other bundle. For comparisons from another agent to $j$, the right value only falls. If an old deletion witness lies in $j$'s bundle, the right value after that deletion still only falls when $g$ is added, by the fixed negative marginal sign in every context. The other witness and no-envy cases are preserved for the same reason. This exhausts all ordered pairs and establishes the induction. Finitely many steps assign every item. ∎
Cake as a common-value equalization resource
If $C=0$, give the entire cake to any one agent and use the item-only EF1 partition. Every cake piece has value zero to every agent, so each pair either has no envy or has its original item-only deletion witness. Both constructions are complete. The measure argument uses only finite atomlessness, so the common-preference subcase also covers singular atomless Borel measures, not merely densities. ∎
VERIFICATION
The executable test generated 200 common-valuation instances with $n=3$ or 4 and six items. Four goods had a nonadditive coverage value (the number of covered features); two chores had additive integer costs. The common cake total was a random integer from 0 to 20 divided by 3. The item allocation used the fixed-sign greedy algorithm and cake values were computed by exact rational water filling. Every ordered pair passed the strong item-only EFM test. No rounding tolerance was used.\begin{lstlisting} assign each common good to a minimum-value bundle assign each common chore to a maximum-value bundle find H with sum(max(0,H-item_value[i])) = common_cake_total for each ordered pair i,j: assert no envy OR (cake_value[j] == 0 AND a valid item-only deletion exists) \end{lstlisting} For $n=1$ no-envy is automatic. For $C=0$, water filling is not invoked with a falsely unique level; the proof uses item EF1 directly. For positive $C$, zero-valued fringes of cake can be attached to a positive-value recipient without affecting comparisons. The common-preference proof cannot be extended merely by setting different $H_i$: agent $i$ evaluates every other agent's piece using its own measure, not that recipient's measure. The test domain is common-valued and cannot detect heterogeneous counterexamples.FINAL
LABEL: UNRESOLVED. The arbitrary heterogeneous doubly monotone statement is not proved or disproved. The strong EFM common-preference theorem, its singular-atomless-measure extension, the common-value EF1/envy-freeability variant, and the large-common-cake sufficient condition are fully proved. The definition-separation example prevents an invalid substitution of weak EFM.Exact first gap. There is no proved mechanism that, for heterogeneous doubly monotone item valuations and heterogeneous nonnegative cake measures, eliminates all envy of positive-cake bundles while preserving an item-only deletion witness for every remaining envy pair.
Three next moves. (1) Prove EF1 plus envy-freeability for two distinct doubly monotone item-valuation types. (2) Extend the common-cake budget lemma to heterogeneous measures with an explicit multi-agent cut feasibility certificate. (3) Search small nonadditive fixed-sign item tables coupled to cake measures with disjoint supports, testing the strong rather than weak fallback.
Minimal possible obstruction. It must use heterogeneity beyond the common-preference theorem; disjoint cake supports and context-dependent item magnitudes are natural stress features. Negative cake densities are outside the main domain and cannot supply a valid counterexample.
Completion Estimate
25%A nonadditive common-preference theorem and several specified variants are proved. Heterogeneous item and cake valuations, which form the main frontier, remain unresolved.
This is a subjective estimate of the fraction of the whole requested mathematical scope addressed by this report, including the named variants. It is not a probability of correctness, an objectively measured fraction of a proof, or an estimate that the remaining work takes the complementary fraction of the time. Only the eleven supplied files are assessed; no missing rank-1--200 statements are inferred.
References
- [cake] H. Aziz, X. Lu, S. Mackenzie and M. Suzuki. Fair Division with Indivisible Goods, Chores, and Cake. arXiv:2511.04891v1 (2025), Definition 2.3 and Section 5. https://arxiv.org/html/2511.04891v1.