This paper introduces a novel multi-agent ski-rental problem that generalizes the classical ski-rental dilemma to a group setting where agents incur individual and shared costs. In our model, each agent can either rent at a fixed daily cost, or purchase a pass at an individual cost, with an additional third option of a discounted group pass available to all. We consider scenarios in which agents' active days differ, leading to dynamic states as agents drop out of the decision process. To address this problem from different perspectives, we define three distinct competitive ratios: overall, state-dependent, and individual rational. For each objective, we design and analyze optimal deterministic and randomized policies. Our deterministic policies employ state-aware threshold functions that adapt to the dynamic states, while our randomized policies sample and resample thresholds from tailored state-aware distributions. The analysis reveals that symmetric policies, in which all agents use the same threshold, outperform asymmetric ones. Our results provide competitive ratio upper and lower bounds and extend classical ski-rental insights to multi-agent settings, highlighting both theoretical and practical implications for group decision-making under uncertainty.

Matching markets are often organized in a multi-stage and decentralized manner. Moreover, participants in real-world matching markets often have uncertain preferences.

We study voting rules for participatory budgeting, where a group of voters collectively decides which projects should be funded using a common budget.

A, B to denote allocations that are exclusively integral and R for randomized allocations. On a high level, the PS-Lottery algorithm uses Birkhoff's We begin by proving a lemma that highlights a connection between not obvious manipulability and randomized mechanisms that output ex-ante proportional allocations. Lemma 5. Inequality (1) (the worst-case guarantee) is satisfied for every randomized mechanism Note that multiple randomized allocations may have the same expected fractional allocation. Recall that, Birkhoff's algorithm, given a square bistochastic matrix, decomposes it into a convex combination (or a lottery) over permutation matrices. Using Lemma 5 we can prove the following theorem.

It is well-understood that, in the absence of monetary transfers, fairness, efficiency and truthfulness cannot be reconciled, in a very strong sense.

We study envy-free policy teaching.

Due to its iconic nature ( i.e ., perceptual resemblance to or natural association with the referent), drawings serve as a powerful tool to communicate concepts transcending language barriers (Fay et al., 2014). In fact, we humans started to use drawings to convey messages dating back to 40,000-60,000 years ago (Hoffmann et al., 2018; Hawkins et al., 2019).

However, unlike QMIX, there are no inherent constraints on factoring the critic. We thus also employ a nonmonotonic factorisation and empirically demonstrate that its increased representational capacity allows it to solve some tasks that cannot be solved with monolithic, or monotonically factored critics.

Multi-agent control is a central theme in the Cyber-Physical Systems (CPS) . However, current control methods either receive non-Markovian states due to insufficient sensing and decentralized design, or suffer from poor convergence.