Second Stop and Sbottom Searches with a Stealth Stop

The top squarks (stops) may be the most wanted particles after the Higgs boson discovery. The searches for the lightest stop have put strong constraints on its mass. However, there is still a search gap in the low mass region if the spectrum of the stop and the lightest neutralino is compressed. In that case, it may be easier to look for the second stop since naturalness requires both stops to be close to the weak scale. The current experimental searches for the second stop are based on the simplified model approach with the decay modes $\tilde{t}_2 \to \tilde{t}_1 Z$ and $\tilde{t}_2 \to \tilde{t}_1 h$. However, in a realistic supersymmetric spectrum there is always a sbottom lighter than the second stop, hence the decay patterns are usually more complicated than the simplified model assumptions. In particular, there are often large branching ratios of the decays $\tilde{t}_2 \to \tilde{b}_1 W$ and $\tilde{b}_1 \to \tilde{t}_1 W$ as long as they are open. The decay chains can be even more complex if there are intermediate states of additional charginos and neutralinos in the decays. By studying several MSSM benchmark models at the 14 TeV LHC, we point out the importance of the multi-$W$ final states in the second stop and the sbottom searches, such as the same-sign dilepton and multilepton signals, aside from the traditional search modes. The observed same-sign dilepton excesses at LHC Run 1 and Run 2 may be explained by some of our benchmark models. We also suggest that the vector boson tagging and a new kinematic variable may help to suppress the backgrounds and increase the signal significance for some search channels. Due to the complex decay patterns and lack of the dominant decay channels, the best reaches likely require a combination of various search channels at the LHC for the second stop and the lightest sbottom.Comment: 46 pages, 9 figures, updated experimental constraints and benchmark points after the ICHEP2016 data, published in JHE

On cooperation structures resulting from simultaneous proposals

This paper looks at cooperation structures that result from a strategic game where players make simultaneous proposals for cooperation. We identify cooperation structures that maximize the potential of the game, and show how the outcome of potential maximization depends on the players' Shapley values. We do not assume superadditivity and hence, potential-maximizing strategy profiles do not always involve full cooperation. In cases where full cooperation does result from potential maximization it can be inefficient. An example provides intuition.cooperation formation game

A Credit Mechanism for Selecting a Unique Competitive Equilibrium

The enlargement of the general-equilibrium structure to allow default subject to penalties to appririate credit limits and default penalties results in a construction of a simple mechanism for a credit using society. We show that there generically exists a price-normalizing bundle that determines a credit money along with appropriate credit limits and default penalties for a credit mechanism to select a unique competitive equilibrium (CE). With some additional conditions, a common credit money can be applied such that any CE can be a unique selection by the credit mechanism with appropriate credit limits default penalties for the traders. This will include a CE with the minimal cash flow penalty. Such CEs are special for the reason that we minimize the need for a substitute-for-trust (i.e. money) in trade.Competitive equilibrium, Credit mechanism, Marginal utility of income, Welfare economics

Trade through endogenous intermediaries

We apply an intermediation game of Townsend (1983) to analyze trade in an exchange economy through endogenous intermediaries. In this game, each trader has the opportunity to become an intermediary by oering to buy or sell unlimited quantities of the commodities at a certain price vector and for a certain group of customers subject to feasibility constraint. An intermediary will not be active unless some of its customers subsequently choose to trade with it. We introduce an "intermediation core" and show that the subgame-perfect equilibrium allocations of the intermediation game are contained in the intermediation core, similar to the inclusion of competitive equilibrium allocations in the core usually studied. We also identify, in terms of the supporting intermediary structures, intermediation core allocations which are also subgame-perfect equilibrium allocations of the intermediation game. These results provide both a characterization and welfare properties of subgame-perfect equilibrium allocations of the intermediation game.intermediation; core; subgame-perfect equilibrium

Selecting a Unique Competitive Equilibrium with Default Penalties

The enlargement of the general-equilibrium structure to allow default subject to penalties results in a construction of a simple mechanism for selecting a unique competitive equilibrium. We consider economies for which a common credit money can be applied to uniquely select any competitive equilibrium with suitable default penalties. We identify two classes of such economies. One consists of economies with utility functions being homogeneous of degree 1; the other consists of economies with the number of consumers equal to the number of commodities and traders having quasi-linear utility functions with respect to different commodities.Competitive equilibrium, Credit mechanism, Marginal utility of income, Welfare economics

On potential maximization as a refinement of Nash equilibrium

We specify an adjustment process that converges to the set of potential-maximizing strategy profiles for 3-player cooperation-formation games or n-player cooperation-formation games based on a superadditive characteristic function. Our analysis provides a justification for potential maximization as a refinement of Nash equilibrium in these settings.adjustment process.

Pitting damage levels estimation for planetary gear sets based on model simulation and grey relational analysis

The planetary gearbox is a critical mechanism in helicopter transmission systems. Tooth failures in planetary gear sets will cause great risk to helicopter operations. A gear pitting damage level estimation methodology has been devised in this paper by integrating a physical model for simulation signal generation, a three-step statistic algorithm for feature selection and damage level estimation for grey relational analysis. The proposed method was calibrated firstly with fault seeded test data and then validated with the data of other tests from a planetary gear set. The estimation results of test data coincide with the actual test records, showing the effectiveness and accuracy of the method in providing a novel way to model based methods and feature selection and weighting methods for more accurate health monitoring and condition prediction