A Local-Dominance Theory of Voting Equilibria

It is well known that no reasonable voting rule is strategyproof. Moreover, the common Plurality rule is particularly prone to strategic behavior of the voters and empirical studies show that people often vote strategically in practice. Multiple game-theoretic models have been proposed to better understand and predict such behavior and the outcomes it induces. However, these models often make unrealistic assumptions regarding voters' behavior and the information on which they base their vote. We suggest a new model for strategic voting that takes into account voters' bounded rationality, as well as their limited access to reliable information. We introduce a simple behavioral heuristic based on \emph{local dominance}, where each voter considers a set of possible world states without assigning probabilities to them. This set is constructed based on prospective candidates' scores (e.g., available from an inaccurate poll). In a \emph{voting equilibrium}, all voters vote for candidates not dominated within the set of possible states. We prove that these voting equilibria exist in the Plurality rule for a broad class of local dominance relations (that is, different ways to decide which states are possible). Furthermore, we show that in an iterative setting where voters may repeatedly change their vote, local dominance-based dynamics quickly converge to an equilibrium if voters start from the truthful state. Weaker convergence guarantees in more general settings are also provided. Using extensive simulations of strategic voting on generated and real preference profiles, we show that convergence is fast and robust, that emerging equilibria are consistent across various starting conditions, and that they replicate widely known patterns of human voting behavior such as Duverger's law. Further, strategic voting generally improves the quality of the winner compared to truthful voting

The Pricing War Continues: On Competitive Multi-Item Pricing

We study a game with \emph{strategic} vendors who own multiple items and a single buyer with a submodular valuation function. The goal of the vendors is to maximize their revenue via pricing of the items, given that the buyer will buy the set of items that maximizes his net payoff. We show this game may not always have a pure Nash equilibrium, in contrast to previous results for the special case where each vendor owns a single item. We do so by relating our game to an intermediate, discrete game in which the vendors only choose the available items, and their prices are set exogenously afterwards. We further make use of the intermediate game to provide tight bounds on the price of anarchy for the subset games that have pure Nash equilibria; we find that the optimal PoA reached in the previous special cases does not hold, but only a logarithmic one. Finally, we show that for a special case of submodular functions, efficient pure Nash equilibria always exist

Minimal Spin-3/2 Dark Matter in a simple ss-channel model

We consider a spin~-~3/2 fermionic dark matter candidate (DM) interacting with Standard Model fermions through a vector mediator in the $s$-channel. We find that for pure vector couplings almost the entire parameter space of the DM and mediator mass consistent with the observed relic density is ruled out by the direct detection observations through DM-nucleon elastic scattering cross-sections. In contrast, for pure axial-vector coupling, the most stringent constraints are obtained from mono-jet searches at the Large Hadron Collider.Comment: 8 pages, 5 figures, Version accepted for publication in EPJ

Spin-3/2 dark matter in a simple tt-channel model

We consider a spin-3/2 fermionic dark matter (DM) particle interacting with the Standard Model quarks through the exchange of a charged and coloured scalar or vector mediator in a simple $t$-channel model. It is found that for the vector mediator case, almost the entire parameter space allowed by the observed relic density is already ruled out by the direct detection LUX data. No such bounds exist on the interaction mediated by scalar particles. Monojet + missing energy searches at the Large Hadron Collider provide the most stringent bounds on the parameters of the model for this case. The collider bounds put a lower limit on the allowed DM masses.Comment: Published EPJC versio

The Concepts of God, Man, and the Environment in Islam: Implications for Islamic Architecture

This paper discusses the concepts of God, man, and the natural environment, as well as some of their implications for Islamic architecture. The paper is divided into eight sections, (1) Introduction: what is Islamic architecture?, (2) Tawhid (God\u27s Oneness), (3) Islam and the role of man on earth, (4) Islam and the environment, (5) The importance of built environment, (6) Peaceful and sustainable coexistence between the environment, architecture and man, (7) The unique soul of Islamic architecture, and (8) Conclusion. The nature of the paper – its content, methodology, and conclusions –, is conceptual and philosophical, rather than empirical. The paper concludes that Islamic architecture is an architecture that through its multidimensionality embodies the message of Islam. It both facilitates the Muslims\u27 realization of the Islamic purpose and its divine principles on earth and promotes a lifestyle generated by such a philosophy and principles. At the core of Islamic architecture lies function with all of its dimensions: corporeal, cerebral and spiritual. The role of the form is an important one too, but only inasmuch as it supplements and enhances function

De novo stone formation in ureteric stump post-nephrectomy

Introduction: The leftover ureteric stump after a simple nephrectomy is rarely symptomatic. Here, we report a unique case of ureteric stump stones that likely developed de novo and patients became symptomatic. Case Report: We report the case of a 53-year-old female, who had benign right nephrectomy for a non-functioning kidney 17 years ago and presented with three years history of recurrent urinary tract infections and right-side abdominal pain. A continuous unenhanced computed tomography scan confirmed the presence of multiple de novo stones in the leftover ureteric stump, which was successfully treated by an open transperitoneal ureteric stumpectomy. She was asymptomatic at 12 months post-operative follow-up. We describe problems of leftover ureteric stumps and the possible pathophysiology of the stones formation in this group of patients. Conclusion: Albeit rare, various symptoms and complications can develop in the leftover stump, including stumpitis, urinary tract infections, and calculi. Therefore, discussion with patients of ureteric stump complications is recommended