200,266 research outputs found

    Study of the Wealth Inequality in the Minority Game

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    To demonstrate the usefulness of physical approaches for the study of realistic economic systems, we investigate the inequality of players' wealth in one of the most extensively studied econophysical models, namely, the minority game (MG). We gauge the wealth inequality of players in the MG by a well-known measure in economics known as the modified Gini index. From our numerical results, we conclude that the wealth inequality in the MG is very severe near the point of maximum cooperation among players, where the diversity of the strategy space is approximately equal to the number of strategies at play. In other words, the optimal cooperation between players comes hand in hand with severe wealth inequality. We also show that our numerical results in the asymmetric phase of the MG can be reproduced semi-analytically using a replica method.Comment: 9 pages in revtex 4 style with 3 figures; minor revision with a change of title; to appear in PR

    The Angular Momentum Distribution within Halos in Different Dark Matter Models

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    We study the angular momentum profile of dark matter halos for a statistical sample drawn from a set of high-resolution cosmological simulations of 2563256^3 particles. Two typical Cold Dark Matter (CDM) models have been analyzed, and the halos are selected to have at least 3×1043\times 10^4 particles in order to reliably measure the angular momentum profile. In contrast with the recent claims of Bullock et al., we find that the degree of misalignment of angular momentum within a halo is very high. About 50 percent of halos have more than 10 percent of halo mass in the mass of negative angular momentum jj. After the mass of negative jj is excluded, the cumulative mass function M(<j)M(<j) follows approximately the universal function proposed by Bullock et al., though we still find a significant fraction of halos (50\sim 50%) which exhibit systematic deviations from the universal function. Our results, however, are broadly in good agreement with a recent work of van den Bosch et al.. We also study the angular momentum profile of halos in a Warm Dark Matter (WDM) model and a Self-Interacting Dark Matter (SIDM) model. We find that the angular momentum profile of halos in the WDM is statistically indistinguishable from that in the CDM model, but the angular momentum of halos in the SIDM is reduced by the self-interaction of dark matter.Comment: 23 pages, 10 figures, 2 tables. Revised version, added a new table, accepted for publication in MNRA

    Subtraction method for NLO corrections in Monte-Carlo event generators for Z boson production

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    We use a subtraction method to construct NLO corrections in a Monte-Carlo event generator for the case of vector boson production in Drell-Yan processes. Our calculations are carried out both for the Bengtsson-Sjostrand-van Zijl (BSZ) algorithm and for a modified algorithm proposed by Collins. In the case of the modified algorithm, we compute the relation between the parton distribution functions and the ones in the MSbar scheme; this relation is the same as the corresponding relation for DIS. For the BSZ algorithm, we show that there is no simple relation.Comment: 16 pages, 4 figures, JHEP class. Misprints correcte

    Decay rate of a Wannier exciton in low dimensional systems

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    The superradiant decay rate of Wannier exciton in one dimensional system is studied. The crossover behavior from 1D chain to 2D film is also examined. It is found that the decay rate shows oscillatory dependence on channel width L. When the quasi 1-D channel is embeded with planar microcavities, it is shown that the dark mode exciton can be examined experimentally.Comment: 12 pages, 1 figur