Analysis of multichannel internet communication.

A novel method employing machine-based learning to identify messages related to other messages is described and evaluated. This technique may enable an analyst to identify and correlate a small number of related messages from a large sample of individual messages. The classic machine learning techniques of decision trees and naive Bayes classification are seeded with few (or no) messages of interest and 'learn' to identify other related messages. The performance of this approach and these specific learning techniques are evaluated and generalized

Games of Incomplete Information and Myopic Equilibria

A new concept of an equilibrium in games is introduced that solves an open question posed by A. Neyman

Neural Circuits Underlying Rodent Sociality: A Comparative Approach

All mammals begin life in social groups, but for some species, social relationships persist and develop throughout the course of an individual’s life. Research in multiple rodent species provides evidence of relatively conserved circuitry underlying social behaviors and processes such as social recognition and memory, social reward, and social approach/avoidance. Species exhibiting different complex social behaviors and social systems (such as social monogamy or familiarity preferences) can be characterized in part by when and how they display specific social behaviors. Prairie and meadow voles are closely related species that exhibit similarly selective peer preferences but different mating systems, aiding direct comparison of the mechanisms underlying affiliative behavior. This chapter draws on research in voles as well as other rodents to explore the mechanisms involved in individual social behavior processes, as well as specific complex social patterns. Contrasts between vole species exemplify how the laboratory study of diverse species improves our understanding of the mechanisms underlying social behavior. We identify several additional rodent species whose interesting social structures and available ecological and behavioral field data make them good candidates for study. New techniques and integration across laboratory and field settings will provide exciting opportunities for future mechanistic work in non-model species

Supersymmetric dark matter in the light of LEP and the Tevatron Collider

We analyze the accelerator constraints on the parameter space of the Minimal Supersymmetric extension of the Standard Model, comparing those now available from LEP II and anticipating the likely sensitivity of Tevatron Run II. The most important limits are those from searches for charginos #chi#"#+-#, neutralinos #chi#_i and Higgs bosons at LEP, and searches for stop squarks, charginos and neutralinos at the Tevatron Collider. We also incorporate the constraints derived from b #-># s#gamma# decay, and discuss the relevance of charge- and colour-breaking minima in the effective potential. We combine and compare the different constraints on the Higgs-mixing parameter #mu#, the gaugino-mass parameter m_1_/_2 and the scalar-mass parameter m_0, incorporating radiative corrections to the physical particle masses. We focus on the resulting limitations on supersymmetric dark matter, assumed to be the lightest neutralino #chi#, incorporating coannihilation effects in the calculation of the relic abundance. We find that m_x > 51 GeV and tan #beta# > 2.2 if all soft supersymmetry-breaking scalar masses are universal, including those of the Higgs bosons, and that these limits weaken to m_x > 46 GeV and tan #beta# > 1.9 if non-universal scalar masses are allowed. Light neutralino dark matter cannot be primarily Higgsino in composition. (orig.)Available from TIB Hannover: RA 2316(2000-05) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Charginos and neutralinos in the light of radiative corrections: sealing the fate of higgsino dark matter

We analyze the LEP constraints from searches for charginos #chi#"#+-# and neutralinos #chi#_i, taking into account radiative corrections to the relations between their masses and the underlying Higgs-mixing and gaugino-mass parameters #mu#, m_1_/_2 and the trilinear mass parameter A_t. Whilst radiative corrections do not alter the excluded domain in m_#chi#"_#+-#" as a function of m_#chi#"_#+-#"-m_#chi#, its mapping into the #mu#, m_1_/_2 plane is altered. We update our previous lower limits on the mass of gaugino dark matter and on tan#beta#, the ratio of Higgs vacuum expectation values, in the light of the latest LEP data and these radiative corrections. We also discuss the viability of Higgsino dark matter, incorporating co-annihilation effects into the calculation of the Higgsino relic abundance. We find that Higgsino dark matter is viable for only a very limited range of #mu# and m_1_/_2, which will be explored completely by upcoming LEP runs. (orig.)27 refs.SIGLEAvailable from TIB Hannover: RR 2916(98-01) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman