arXiv subjects

Yuki Tamura

Publications and source records attributed to Yuki Tamura.

5 recordsLinked to original sources

arXiv2025

Characterizing the ELS Values with Fixed-Population Invariance Axioms

We study efficient, linear, and symmetric (ELS) values, a central family of allocation rules for cooperative games with transferable-utility (TU-games) that includes the Shapley value, the CIS value, and the ENSC value. We first show that every ELS value can be written as the Shapley value of a suitably transformed TU-game. We then introduce three types of invariance axioms for fixed player populations. The first type consists of composition axioms, and the second type is active-player consistency. Each of these two types yields a characterization of a subclass of the ELS values that contains the family of least-square values. Finally, the third type is nullified-game consistency: we define three such axioms, and each axiom yields a characterization of one of the Shapley, CIS, and ENSC values.

econ.TH↗

arXiv2025

Characterizations of Proportional Division Value in TU-Games via Fixed-Population Consistency

We study the proportional division value in TU-games, which distributes the grand coalition worth in proportion to the players' stand-alone worths. Focusing on fixed-population consistency, we characterize the proportional division value through three types of axioms: axioms concerning transformations of the grand coalition worth, composition axioms, and nullified-game consistency. The first type captures how payoffs respond when the grand coalition worth changes. The composition axioms require that the outcome be the same whether a game is solved directly or through a two-step procedure based on a reference allocation and an associated adjustment of the game. Nullified-game consistency requires that, when some players' payoffs are fixed, the solution for the remaining players in the adjusted game coincides with their original payoffs. Together with efficiency and/or fairness-related conditions where appropriate, these axioms characterize the proportional division value.

econ.TH↗

arXiv2025

TTC Domains

For the object reallocation problem, we study whether characterizations of Top Trading Cycles (TTC) based on individual rationality, efficiency, and strategyproofness on the unrestricted domain extend to restricted preference domains. We introduce the top-two condition and show that it offers a useful criterion for answering this question. The condition requires that, within every subset of objects, any two objects that can each be ranked first can also be ranked as the top two, in both possible orders. We first show that this condition is sufficient: on every domain satisfying the top-two condition, TTC is the unique rule satisfying the relevant axioms. We also provide a partial converse. For domains that fail the top-two condition within a small subset of objects and satisfy a mild extension condition, we construct a rule distinct from TTC satisfying these axioms. Our results provide a unifying perspective on existing findings for specific domains, such as the single-peaked and single-dipped domains, while also addressing several previously unexplored domains, including the circular and partial-agreement domains.

econ.TH↗

arXiv2024

Development of fall prevention training device that can provide external disturbance to the ankle with pneumatic gel muscles (PGM) while walking

Although the average life expectancy in Japan has been increasing in recent years, the problem of the large gap between healthy life expectancy and average life expectancy is still unresolved. Among the factors that lead to the need for nursing care, injuries due to falls account for a certain percentage of the total. In this paper, we developed boots that can provide external disturbance to the ankle with pneumatic gel muscles (PGM) while walking. We experimented using an angular velocity and acceleration of the heel as evaluation indices to evaluate the effectiveness of fall prevention training using this device, which is smaller and more wearable than conventional devices. In this study, we confirmed that the developed system has enough training intensity to significantly affect the gait waveform.

cs.HC↗

arXiv2022

The Crawler: Three Equivalence Results for Object (Re)allocation Problems when Preferences Are Single-peaked

For object reallocation problems, if preferences are strict but otherwise unrestricted, the Top Trading Cycles rule (TTC) is the leading rule: It is the only rule satisfying efficiency, individual rationality, and strategy-proofness. However, on the subdomain of single-peaked preferences, Bade (2019) defines a new rule, the "crawler", which also satisfies these three properties. (i) The crawler selects an allocation by "visiting" agents in a specific order. A natural "dual" rule can be defined by proceeding in the reverse order. Our first theorem states that the crawler and its dual are actually the same. (ii) Single-peakedness of a preference profile may in fact hold for more than one order and its reverse. Our second theorem states that the crawler is invariant to the choice of the order. (iii) For object allocation problems (as opposed to reallocation problems), we define a probabilistic version of the crawler by choosing an endowment profile at random according to a uniform distribution, and applying the original definition. Our third theorem states that this rule is the same as the "random priority rule".

econ.TH↗