Asymmetric Conflicts with Endogenous Dimensionality

This article examines a two-stage model of asymmetric conflict based on the classic Colonel Blotto game in which players have, in the first stage, the ability to increase the number of battlefields contested. It thereby endogenizes the “dimensionality” of conflict. In equilibrium, if the asymmetry in the players’ resource endowments exceeds a threshold, the weak player chooses to add battlefields, while the strong player never does. Adding battlefields spreads the strong player’s forces more thinly, increasing the incidence of favorable strategic mismatches for the weak player.Asymmetric Conflict, Multi-battle Conflict, Colonel Blotto Game, Stochastic Guerilla Warfare, Endogenous Dimensionality

Feasibility and efficacy of early lung cancer diagnosis with chest computed tomography in HIV-infected smokers

International audienceOBJECTIVE: Lung cancer screening with chest computed tomography (CT) is beneficial in smokers aged 55 to 74 years. We studied the risks, benefits and feasibility of early lung cancer diagnosis with CT in HIV-infected smokers. DESIGN AND SETTING: French, multicentre, single round chest CT study in France, realized between February 2011 and June 2012. PARTICIPANTS: Patients were HIV-infected smokers at least 40 years, at least 20 pack-years, with a CD4 T-lymphocyte nadir count below 350 cells/μl. INTERVENTION: Single chest CT with a proposed standardized workup algorithm of positive images. MAIN OUTCOME MEASURE: The outcome was the number of histologically proven lung cancers diagnosed by CT with a 2-year follow-up. RESULTS: Median age of the 442 included patients was 49.8 years, 81.6% were under 55 years, 84% were men, median smoking was 30 pack-years, median nadir and last CD4 cell counts were 168 and 574 cells/μl, respectively, and 90% of patients had a plasma HIV RNA below 50 copies/ml. A positive image at baseline was reported in 94 (21%) patients, and 15 (3.4%) patients had 18 invasive procedures with no serious adverse events. Lung cancer was diagnosed in 10 patients (six at early stages), of which nine (2.0%, 95% confidence interval: 0.9-3.8) were CT detected, and eight in patients below 55 years. CONCLUSION: Early lung cancer diagnosis with CT in HIV-infected smokers was feasible, safe, and yielded a significant number of cancers. Lung cancer screening of HIV-infected smokers with an important history of immunodeficiency revealed a substantial number of cancers at younger ages than the targeted range in the general populatio

Investigating the potentially contradictory microfoundations of financialization

The existing academic literature on financialization points to multiple instances in which firms attempt to demonstrate the vitality of their stock-market position in ways which ultimately prove to be self-harming. I demonstrate, in the first instance as a matt er of immanent logic, that these actions are linked to the interplay of contradictory tendencies in the microfoundations of financialization. Under conditions of financialization, firms create additional sources of credit to capitalize their productive activities by driving their stock price into greater increases than the market average, thereby generating capital gains. Yet, the more it becomes public knowledge that the financing tricks used to inflate the stock price provide no productive benefit to the firm, the more it would seem to create incentives for fund managers to hold portfolios that replicate the stock market as a whole. In this way, they will minimize their exposure to financial misrepresentation. Such a stance undermines financialized business models, but it does in any case conform to fund managers' basic theoretical training, which revolves around the logical demonstration that an individual stock cannot systematically out-perform the market average. I review the available empirical studies of fund manager decision-making to show that they find against the existence of a simple performativity loop operating between finance theory and fund manager behaviour. However, on many points the empirical evidence does confirm the theoretically derived conclusion concerning the potentially contradictory microfoundations of financialization. Fund managers often do act in a way which is consistent with finance theory's core claim that an index-tracking strategy represents the only equilibrium portfolio, even if this is only rarely as a result of the direct performativity of the theory

Index Cohesive Force Analysis Reveals That the US Market Became Prone to Systemic Collapses Since 2002

BACKGROUND: The 2007-2009 financial crisis, and its fallout, has strongly emphasized the need to define new ways and measures to study and assess the stock market dynamics. METHODOLOGY/PRINCIPAL FINDINGS: The S&P500 dynamics during 4/1999-4/2010 is investigated in terms of the index cohesive force (ICF--the balance between the stock correlations and the partial correlations after subtraction of the index contribution), and the Eigenvalue entropy of the stock correlation matrices. We found a rapid market transition at the end of 2001 from a flexible state of low ICF into a stiff (nonflexible) state of high ICF that is prone to market systemic collapses. The stiff state is also marked by strong effect of the market index on the stock-stock correlations as well as bursts of high stock correlations reminiscence of epileptic brain activity. CONCLUSIONS/SIGNIFICANCE: The market dynamical states, stability and transition between economic states was studies using new quantitative measures. Doing so shed new light on the origin and nature of the current crisis. The new approach is likely to be applicable to other classes of complex systems from gene networks to the human brain

Inference of financial networks using the normalised mutual information rate

In this paper we study data from financial markets using an information theory tool that we call the normalised Mutual Information Rate and show how to use it to infer the underlying network structure of interrelations in foreign currency exchange rates and stock indices of 14 countries world-wide and the European Union. We first present the mathematical method and discuss about its computational aspects, and then apply it to artificial data from chaotic dynamics and to correlated random variates. Next, we apply the method to infer the network structure of the financial data. Particularly, we study and reveal the interrelations among the various foreign currency exchange rates and stock indices in two separate networks for which we also perform an analysis to identify their structural properties. Our results show that both are small-world networks sharing similar properties but also having distinct differences in terms of assortativity. Finally, the consistent relationships depicted among the 15 economies are further supported by a discussion from the economics view point

Cultural transmission and biological markets

Active cultural transmission of fitness-enhancing behavior (sometimes called “teaching”) can be seen as a costly strategy: one for which its evolutionary stability poses a Darwinian puzzle. In this article, we offer a biological market model of cultural transmission that substitutes or complements existing kin selection-based proposals for the evolution of cultural capacities. We explicitly demonstrate how a biological market can account for the evolution of teaching when individual learners are the exclusive focus of social learning (such as in a fast-changing environment). We also show how this biological market can affect the dynamics of cumulative culture. The model works best when it is difficult to have access to the observation of the behavior without the help of the actor. However, in contrast to previous non-mathematical hypotheses for the evolution of teaching, we show how teaching evolves even when innovations are insufficiently opaque and therefore vulnerable to acquisition by emulators via inadvertent transmission. Furthermore, teaching in a biological market is an important precondition for enhancing individual learning abilitie