438 research outputs found
Piecewise smooth systems near a co-dimension 2 discontinuity manifold: can one say what should happen?
We consider a piecewise smooth system in the neighborhood of a co-dimension 2
discontinuity manifold . Within the class of Filippov solutions, if
is attractive, one should expect solution trajectories to slide on
. It is well known, however, that the classical Filippov
convexification methodology is ambiguous on . The situation is further
complicated by the possibility that, regardless of how sliding on is
taking place, during sliding motion a trajectory encounters so-called generic
first order exit points, where ceases to be attractive.
In this work, we attempt to understand what behavior one should expect of a
solution trajectory near when is attractive, what to expect
when ceases to be attractive (at least, at generic exit points), and
finally we also contrast and compare the behavior of some regularizations
proposed in the literature.
Through analysis and experiments we will confirm some known facts, and
provide some important insight: (i) when is attractive, a solution
trajectory indeed does remain near , viz. sliding on is an
appropriate idealization (of course, in general, one cannot predict which
sliding vector field should be selected); (ii) when loses attractivity
(at first order exit conditions), a typical solution trajectory leaves a
neighborhood of ; (iii) there is no obvious way to regularize the
system so that the regularized trajectory will remain near as long as
is attractive, and so that it will be leaving (a neighborhood of)
when looses attractivity.
We reach the above conclusions by considering exclusively the given piecewise
smooth system, without superimposing any assumption on what kind of dynamics
near (or sliding motion on ) should have been taking place.Comment: 19 figure
Food scares in an uncertain world
This is the accepted version of the following article: Food scares in an uncertain world. Journal of the European Economic Association, Volume 11, Issue 6, pages 1432–1456, December 2013, which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1111/jeea.12057/abstrac
Food scares in an uncertain world
This is the accepted version of the following article: Food scares in an uncertain world. Journal of the European Economic Association, Volume 11, Issue 6, pages 1432–1456, December 2013, which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1111/jeea.12057/abstrac
Quantum decision making by social agents
The influence of additional information on the decision making of agents, who
are interacting members of a society, is analyzed within the mathematical
framework based on the use of quantum probabilities. The introduction of social
interactions, which influence the decisions of individual agents, leads to a
generalization of the quantum decision theory developed earlier by the authors
for separate individuals. The generalized approach is free of the standard
paradoxes of classical decision theory. This approach also explains the
error-attenuation effects observed for the paradoxes occurring when decision
makers, who are members of a society, consult with each other, increasing in
this way the available mutual information. A precise correspondence between
quantum decision theory and classical utility theory is formulated via the
introduction of an intermediate probabilistic version of utility theory of a
novel form, which obeys the requirement that zero-utility prospects should have
zero probability weights.Comment: This paper has been withdrawn by the authors because a much extended
and improved version has been submitted as arXiv:1510.02686 under the new
title "Role of information in decision making of social agents
How brains make decisions
This chapter, dedicated to the memory of Mino Freund, summarizes the Quantum
Decision Theory (QDT) that we have developed in a series of publications since
2008. We formulate a general mathematical scheme of how decisions are taken,
using the point of view of psychological and cognitive sciences, without
touching physiological aspects. The basic principles of how intelligence acts
are discussed. The human brain processes involved in decisions are argued to be
principally different from straightforward computer operations. The difference
lies in the conscious-subconscious duality of the decision making process and
the role of emotions that compete with utility optimization. The most general
approach for characterizing the process of decision making, taking into account
the conscious-subconscious duality, uses the framework of functional analysis
in Hilbert spaces, similarly to that used in the quantum theory of
measurements. This does not imply that the brain is a quantum system, but just
allows for the simplest and most general extension of classical decision
theory. The resulting theory of quantum decision making, based on the rules of
quantum measurements, solves all paradoxes of classical decision making,
allowing for quantitative predictions that are in excellent agreement with
experiments. Finally, we provide a novel application by comparing the
predictions of QDT with experiments on the prisoner dilemma game. The developed
theory can serve as a guide for creating artificial intelligence acting by
quantum rules.Comment: Latex file, 20 pages, 3 figure
Duhemian Themes in Expected Utility Theory
This monographic chapter explains how expected utility (EU) theory arose in von Neumann and Morgenstern, how it was called into question by Allais and others, and how it gave way to non-EU theories, at least among the specialized quarters of decion theory. I organize the narrative around the idea that the successive theoretical moves amounted to resolving Duhem-Quine underdetermination problems, so they can be assessed in terms of the philosophical recommendations made to overcome these problems. I actually follow Duhem's recommendation, which was essentially to rely on the passing of time to make many experiments and arguments available, and evebntually strike a balance between competing theories on the basis of this improved knowledge. Although Duhem's solution seems disappointingly vague, relying as it does on "bon sens" to bring an end to the temporal process, I do not think there is any better one in the philosophical literature, and I apply it here for what it is worth.
In this perspective, EU theorists were justified in resisting the first attempts at refuting their theory, including Allais's in the 50s, but they would have lacked "bon sens" in not acknowledging their defeat in the 80s, after the long process of pros and cons had sufficiently matured.
This primary Duhemian theme is actually combined with a secondary theme - normativity. I suggest that EU theory was normative at its very beginning and has remained so all along, and I express dissatisfaction with the orthodox view that it could be treated as a straightforward descriptive theory for purposes of prediction and scientific test. This view is usually accompanied with a faulty historical reconstruction, according to which EU theorists initially formulated the VNM axioms descriptively and retreated to a normative construal once they fell threatened by empirical refutation. From my historical study, things did not evolve in this way, and the theory was both proposed and rebutted on the basis of normative arguments already in the 1950s. The ensuing, major problem was to make choice experiments compatible with this inherently normative feature of theory. Compability was obtained in some experiments, but implicitly and somewhat confusingly, for instance by excluding overtly incoherent subjects or by creating strong incentives for the subjects to reflect on the questions and provide answers they would be able to defend.
I also claim that Allais had an intuition of how to combine testability and normativity, unlike most later experimenters, and that it would have been more fruitful to work from his intuition than to make choice experiments of the naively empirical style that flourished after him.
In sum, it can be said that the underdetermination process accompanying EUT was resolved in a Duhemian way, but this was not without major inefficiencies. To embody explicit rationality considerations into experimental schemes right from the beginning would have limited the scope of empirical research, avoided wasting resources to get only minor findings, and speeded up the Duhemian process of groping towards a choice among competing theories
Investigation of livestock for presence of Trypanosoma brucei gambiense in Tafa Local Government Area of Niger State, Nigeria
The study investigated the presence of Trypanosoma brucei gambiense in livestock to ascertain their reservoir role and also screened for other pathogenic trypanosomes of animals in Tafa Local Government Area of Niger state, Nigeria. A total of 460 livestock comprising (cattle, sheep, goats, and dogs) selected at random were bled, examined using the buffy coat and Giemsa stained thin film and packed cell volume estimated. Questionnaire was filled for each animal on demography, awareness and management practices. An overall prevalence of 2.17% with Trypanosoma brucei, T. congolense, T. vivax and a mixed infection of T. brucei and T. congolense observed microscopically awaiting characterization. Interviews revealed high awareness (82.8%) of tsetse and trypanosomiasis described as bush disease and abortion in four cows. The PCV values were within the normal range, however, a significant decrease (P<0.05) was observed in sheep aged 7months to 4years in two communities. Therefore, the study indicated the presence of T. brucei and other trypanosomes suggesting that animal trypanosomiasis is still a problem to animal health and wellbeing in the study area. The study recommends effective integrated chemotherapy and vector control including livestock rearing under intensive management system to boost livestock production and productivity
Paradoxes and Mechanisms for Choice under Risk
Experiments on choice under risk typically involve multiple decisions by individual subjects. The choice of mechanism for selecting decision(s) for payoff is an essential design feature unless subjects isolate each one of the multiple decisions. We report treatments with different payoff mechanisms but the same decision tasks. The data show large differences across mechanisms in subjects’ revealed risk preferences, a clear violation of isolation. We illustrate the importance of these mechanism effects by identifying their implications for classical tests of theories of decision under risk. We discuss theoretical properties of commonly used mechanisms, and new mechanisms introduced herein, in order to clarify which mechanisms are theoretically incentive compatible for which theories. We identify behavioral properties of some mechanisms that can introduce bias in elicited risk preferences – from cross-task contamination – even when the mechanism used is theoretically incentive compatible. We explain that selection of a payoff mechanism is an important component of experimental design in many topic areas including social preferences, public goods, bargaining, and choice under uncertainty and ambiguity as well as experiments on decisions under risk
- …