In: Europhysics Letters, 2009, vol. 88, no. 6, p. 68008
In some recommender systems where users can vote objects by ratings, the similarity between users can be quantified by a benchmark index, namely the Pearson correlation coefficient, which reflects the rating correlations. Another alternative way is to calculate the similarity based solely on the relevance information, namely whether a user has voted an object. The former one uses more information...
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In: Europhysics Letters, 2008, vol. 82, no. 5, p. 58007
Recommender systems are significant to help people deal with the world of information explosion and overload. In this letter, we develop a general framework named self-consistent refinement and implement it by embedding two representative recommendation algorithms: similarity-based and spectrum-based methods. Numerical simulations on a benchmark data set demonstrate that the present method...
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In: Physica C: Superconductivity, 2007, vol. 460-462, no. 2, p. 1153-1154
A trial wave function is proposed for studying the instability of the two-dimensional Hubbard model with respect to d-wave superconductivity. Double occupancy is reduced in a similar way as in previous variational studies, but in addition our wave function both enhances the delocalization of holes and induces a kinetic exchange between the electron spins. These refinements lead to a large energy...
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In: Physica A: Statistical Mechanics and its Applications, 2006, vol. 365, no. 2, p. 529-542
Minority games where groups of agents remember, react or incorporate information with different timescales are investigated. We support our findings by analytical arguments whenever possible.
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In: Physica A: Statistical and Theoretical Physics, 2006, vol. 371, no. 2, p. 732-744
Advances in information technology reduce barriers to information propagation, but at the same time they also induce the information overload problem. For the making of various decisions, mere digestion of the relevant information has become a daunting task due to the massive amount of information available. This information, such as that generated by evaluation systems developed by various web...
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In: Europhysics Letters, 2006, vol. 75, no. 6, p. 1006-1012
With the explosive growth of accessible information, expecially on the Internet, evaluation-based filtering has become a crucial task. Various systems have been devised aiming to sort through large volumes of information and select what is likely to be more relevant. In this letter we analyse a new ranking method, where the reputation of information providers is determined self-consistently.
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In: Physica A: Statistical Mechanics and its Applications, 2004, vol. 332, p. 519-532
Is visitors’ attendance a fair indicator of a web site's quality? Internet sub-domains are usually characterized by power-law distributions of visits, thus suggesting a rich-get-richer process. If this is the case, the number of visits is not a relevant measure of quality. If, on the other hand, there are active players, i.e., visitors who can tell the value of the information available, better...
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In: Physica A: Statistical Mechanics and its Applications, 2004, vol. 338, p. 596-604
We analyze different methods of sorting and selecting a set of objects by their intrinsic value, via pairwise comparisons whose outcome is uncertain. After discussing the limits of repeated Round Robins, two new methods are presented: The ran-fil requires no previous knowledge on the set under consideration, yet displaying good performances even in the least favorable case. The min-ent method...
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In: Physica A: Statistical Mechanics and its Applications, 2005, vol. 345, no. 3-4, p. 705-712
We analyze some voting models mimicking online evaluation systems intended to reduce the information overload. The minimum number of operations needed for a system to be effective is analytically estimated. When herding effects are present, linear preferential attachment marks a transition between trustful and biased reputations.
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